【MVVM】Data Binding高级用法-Observable、动态生成Binding Class（三）

本文主要是介绍【MVVM】Data Binding高级用法-Observable、动态生成Binding Class（三），希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

设置View的id

虽然说Data Binding这种分层模式使得我们对数据的传递简单明了，一般情况下我们可以不设置View的id，不使用findViewById即可对View进行数据上一系列的操作，不过有时候根据情况我们需要对某些View设置id，但是还是可以不findViewById即可得到该控件的对象，因为设置id后ViewDataBinding类会自动生成对应的控件对象，如：

<code class="hljs xml has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">layout</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">xmlns:android</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"http://schemas.android.com/apk/res/android"</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">data</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">variable</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">name</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"user"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">type</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"com.sunzxyong.User"</span>/></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">data</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">LinearLayout
</span>       <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:orientation</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"vertical"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_width</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"match_parent"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_height</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"match_parent"</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">TextView</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_width</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"wrap_content"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_height</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"wrap_content"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:text</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"@{user.userName}"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:id</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"@+id/userName"</span>/></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">TextView</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_width</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"wrap_content"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_height</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"wrap_content"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:text</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"@{user.userPassword}"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:id</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"@+id/userPassword"</span>/></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">LinearLayout</span>></span>
<span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">layout</span>></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li></ul>

那么在ViewDataBinding类中会自动生成相应的控件对象：

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> TextView userName;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> TextView userPassword;</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

这些对象名和id名是一样的，然后我们可以通过：

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">ActivityMainBinding mBinding = DataBindingUtil<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setContentView</span>(this, R<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.layout</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.activity</span>_main)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
TextView mTvUserName = mBinding<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.userName</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
TextView mTvPassword = mBinding<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.userPassword</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

即可得到TextView的对象了，再进行后续操作。。。

Observable观察者

我们知道，Data Binding中如果我们直接修改Model实体对象（也就是POJO）中的数据，这些数据并不能直接更新到UI，所以Data Binding给了我们一套很好的通知机制，分别有三类： Observable objects, observable fields, and observable collections，分别表示观察对象、观察字段、观察集合，若相应的对象、字段、集合中数据变化时候，那么UI将会自动更新数据。下面我们一一来介绍它们的用法：

Observable objects

因为Observable是个接口，Google为我们提供了一个BaseObservable类，我们只要把Model类继承自它就获得了通知UI更新数据的能力了，然后再getter方法上添加Bindable注解，在setter方法中使用notifying提醒UI更新数据。如：

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">User</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">BaseObservable</span> {</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> String userName;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> String userPassword;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">User</span>(String userName, String userPassword) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.userName = userName;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.userPassword = userPassword;}<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Bindable</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> String <span class="hljs-title" style="box-sizing: border-box;">getUserName</span>() {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> userName;}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">setUserName</span>(String userName) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.userName = userName;notifyPropertyChanged(BR.userName);}<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Bindable</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> String <span class="hljs-title" style="box-sizing: border-box;">getUserPassword</span>() {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> userPassword;}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">setUserPassword</span>(String userPassword) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.userPassword = userPassword;notifyPropertyChanged(BR.userPassword);}
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li></ul>

首先我们需要在getter方法上添加Bindable注解后，Bindable注解会自动生成一个BR类，该类位于app module包下，通过BR类我们设置更新的数据，当Model中的数据发生变化时，setter方法中的notifyPropertyChanged()就会通知UI更新数据了。

下面我们通过一个Demo来看看效果吧： 
原先的User类： 
我们没有继承BaseObservable

<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> User  {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> String userName;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> String userPassword;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">User</span>(String userName, String userPassword) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.userName = userName;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.userPassword = userPassword;}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> String <span class="hljs-title" style="box-sizing: border-box;">getUserName</span>() {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> userName;}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">setUserName</span>(String userName) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.userName = userName;}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> String <span class="hljs-title" style="box-sizing: border-box;">getUserPassword</span>() {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> userPassword;}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">setUserPassword</span>(String userPassword) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.userPassword = userPassword;}}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li></ul>

然后onCreate()方法中代码为：

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onCreate</span>(Bundle savedInstanceState) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.onCreate(savedInstanceState);ActivityMainBinding mBinding = DataBindingUtil.setContentView(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>, R.layout.activity_main);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> User user = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> User(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Sunzxyong"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"12345678"</span>);mBinding.setUser(user);<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//点击按钮改变User的数据</span>mBinding.btn.setOnClickListener(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> android.view.View.OnClickListener() {<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onClick</span>(android.view.View v) {user.setUserName(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Hello"</span>);user.setUserPassword(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"87654321"</span>);}});}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li></ul>

效果如下： 
 
我们无论怎么点击UI界面上都没有更新数据。。。

那么我们把User类继承自BaseObservable：

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">User</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">BaseObservable</span> {</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> String userName;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> String userPassword;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">User</span>(String userName, String userPassword) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.userName = userName;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.userPassword = userPassword;}<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Bindable</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> String <span class="hljs-title" style="box-sizing: border-box;">getUserName</span>() {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> userName;}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">setUserName</span>(String userName) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.userName = userName;notifyPropertyChanged(BR.userName);}<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Bindable</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> String <span class="hljs-title" style="box-sizing: border-box;">getUserPassword</span>() {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> userPassword;}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">setUserPassword</span>(String userPassword) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.userPassword = userPassword;notifyPropertyChanged(BR.userPassword);}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li></ul>

onCreate()的代码还是一样：

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"> protected void onCreate(Bundle savedInstanceState) {super<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.onCreate</span>(savedInstanceState)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">com</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.sunzxyong</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.binding</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.databinding</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ActivityMainBinding</span> mBinding = DataBindingUtil<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setContentView</span>(this, R<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.layout</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.activity</span>_main)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>final User user = new User(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Sunzxyong"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"12345678"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mBinding<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setUser</span>(user)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mBinding<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.btn</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setOnClickListener</span>(new android<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.view</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.View</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.OnClickListener</span>() {@Overridepublic void onClick(android<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.view</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.View</span> v) {user<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setUserName</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Hello"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>user<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setUserPassword</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"87654321"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>}})<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li></ul>

效果如下： 

可以看到Model中的数据更新时UI界面上的数据也同时更新了。

ObservableFields

我们刚刚介绍的通知UI更新的方法是用User类继承自BaseObservable，然后在getter上添加注解、在setter中添加notify方法，这感觉总是有点麻烦，步骤繁琐，于是，Google推出ObservableFields类，使用它我们可以简化我们的Model类，如：

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">User</span>{</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> ObservableField<String> userName = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ObservableField<>();<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> ObservableField<String> userPassword = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ObservableField<>();
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

没错刚刚那一堆代码就变成了两行，然后通过：

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">User user = new User()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
user<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.userName</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.set</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"sunzxyong"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
user<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.userPassword</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.set</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"12345678"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
String userName = user<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.userName</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.get</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
String userPassword = user<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.userPassword</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.get</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>

来设置和获取数据，这样就简便多了。于是onCreate()方法中的代码就变成了这样：

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">protected void onCreate(Bundle savedInstanceState) {super<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.onCreate</span>(savedInstanceState)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>ActivityMainBinding mBinding = DataBindingUtil<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setContentView</span>(this, R<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.layout</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.activity</span>_main)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>final User user = new User()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>user<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.userName</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.set</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"sunzxyong"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>user<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.userPassword</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.set</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"12345678"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mBinding<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setUser</span>(user)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mBinding<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.btn</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setOnClickListener</span>(new android<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.view</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.View</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.OnClickListener</span>() {@Overridepublic void onClick(android<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.view</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.View</span> v) {user<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.userName</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.set</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"hello"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>user<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.userPassword</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.set</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"87654321"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>}})<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li></ul>

我们还是来看一下效果： 
 
UI还是正常更新数据。 
当然ObservableField<T>中传入的泛型可以是java中的基本类型，当然我们还可以使用 ObservableBoolean, ObservableByte, ObservableChar, ObservableShort, ObservableInt, ObservableLong, ObservableFloat, ObservableDouble, ObservableParcelable等具体的类型，效果也和ObservableField<T>是一样的，如：

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">User</span>{</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> ObservableField<String> userName = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ObservableField<>();<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> ObservableField<Integer> userPassword = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ObservableField<>();<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> ObservableInt userAge = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ObservableInt();
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>

Observable Collections

Google也为我们提供了一些通知类型的集合，有这三种：ObservableArrayList<T>、ObservableArrayMap<K,V>、ObservableMap<K,V>，它和平场使用的List、Map用法一样，但是多了通知功能。 
我们在layout中的<data>区域导入包后就可以直接用它了，当它内部的数据发生改变时就自动会通知UI界面更新。如：

<code class="hljs lasso has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;"><</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">data</span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">></span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;"><</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">type</span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span><span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"android.databinding.ObservableMap"</span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">/</span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">></span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;"><</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">type</span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span><span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"com.sunzxyong.binding.Keys"</span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">/</span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">></span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;"><</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">variable</span>name<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span><span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"map"</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">type</span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span><span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"ObservableMap&lt;String,Object>"</span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">/</span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">></span>
<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;"><</span>/<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">data</span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">></span>
<span class="hljs-attribute" style="box-sizing: border-box;">...</span><span class="hljs-attribute" style="box-sizing: border-box;">...</span>
<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;"><</span>TextViewandroid:layout_width<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span><span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"wrap_content"</span>android:layout_height<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span><span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"wrap_content"</span>android:text<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span><span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"@{map[Keys.name]}"</span> <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">/</span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">></span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;"><</span>TextViewandroid:layout_width<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span><span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"wrap_content"</span>android:layout_height<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span><span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"wrap_content"</span>android:text<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span><span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"@{String.valueOf(1+(Integer)map[Keys.age])}"</span> <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">/</span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li></ul>

我来看一个Demo，使用ObservableMap<K,V>，当map中的数据改变时候同时也通知了UI界面更新。 
xml布局为：

<code class="hljs xml has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">layout</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">xmlns:android</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"http://schemas.android.com/apk/res/android"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">xmlns:tools</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"http://schemas.android.com/tools"</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">data</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">import</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">type</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"android.databinding.ObservableMap"</span>/></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">import</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">type</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"com.sunzxyong.binding.Keys"</span>/></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">variable
</span>            <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">name</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"map"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">type</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"ObservableMap&lt;String,Object>"</span>/></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">data</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">LinearLayout
</span>        <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_width</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"match_parent"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_height</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"match_parent"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:orientation</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"vertical"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">tools:context</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">".MainActivity"</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">TextView
</span>            <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_width</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"wrap_content"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_height</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"wrap_content"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:text</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"@{map[Keys.name]}"</span> /></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">TextView
</span>            <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_width</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"wrap_content"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_height</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"wrap_content"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:text</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"@{String.valueOf(1+(Integer)map[Keys.age])}"</span> /></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">Button
</span>            <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:id</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"@+id/btn"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_marginTop</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"30dp"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_width</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"wrap_content"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_height</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"wrap_content"</span><span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:text</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"changeData"</span> /></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">LinearLayout</span>></span>
<span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">layout</span>></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li></ul>

onCreate()方法：

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">    protected void onCreate(Bundle savedInstanceState) {super<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.onCreate</span>(savedInstanceState)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>ActivityMainBinding mBinding = DataBindingUtil<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setContentView</span>(this, R<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.layout</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.activity</span>_main)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>final ObservableMap<String, Object> map = new ObservableArrayMap<>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.put</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"name"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"sunzxyong"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.put</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"age"</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">22</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mBinding<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setMap</span>(map)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mBinding<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.btn</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setOnClickListener</span>(new android<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.view</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.View</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.OnClickListener</span>() {@Overridepublic void onClick(android<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.view</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.View</span> v) {map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.put</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"name"</span>,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"hello"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>map<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.put</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"age"</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">20</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>}})<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li></ul>

Keys类：

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Keys</span>{</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> String name = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"name"</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> String age = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"age"</span>;
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

效果： 

创建Binding类

我们将数据绑定到xml文件后，Binding类是自动根据xml布局文件名生成的（继承自android.databinding.ViewDataBinding），我们创建Binding对象一般有以下几种方法：

1. 直接使用自动创建的Binding类创建

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">MyLayoutBinding binding = MyLayoutBinding<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.inflate</span>(layoutInflater)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
MyLayoutBinding binding = MyLayoutBinding<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.inflate</span>(layoutInflater, viewGroup, false)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

1. 绑定根布局View

<code class="hljs fix has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-attribute" style="box-sizing: border-box;">MyLayoutBinding binding </span>=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;"> MyLayoutBinding.bind(viewRoot);</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

1. 使用DataBindingUtil创建

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">ViewDataBinding binding = DataBindingUtil<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.inflate</span>(LayoutInflater, layoutId,parent, attachToParent)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
ViewDataBinding binding = DataBindingUtil<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.bindTo</span>(viewRoot, layoutId)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

Dynamic Variables动态变量

根据Google官方文档：

At times, the specific binding class won’t be known. For example, a RecyclerView.Adapter operating against arbitrary layouts won’t know the specific binding class. It still must assign the binding value during the onBindViewHolder(VH, int).

说明在使用ListView、GridView、RecyclerView的时候，由于绑定的类不能确定，比如RecyclerView只有在onBindViewHolder()方法中才能确定绑定的Item，所以我们只有在该办法中动态得到Binding Class（ViewModel）、动态绑定数据。方法是： 
1、先创建好一个item布局，在布局中绑定数据：

<code class="hljs r has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><?xml version=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"1.0"</span> encoding=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"utf-8"</span>?>
<layout xmlns:android=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"http://schemas.android.com/apk/res/android"</span>><data><variablename=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"user"</span>type=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"com.sunzxyong.binding.model.User"</span>/></data><LinearLayout<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span>><TextViewandroid:layout_width=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"wrap_content"</span>android:layout_height=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"wrap_content"</span>android:text=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"@{user.userName}"</span>android:textSize=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"20sp"</span>android:textColor=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"#ffffff"</span> />
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span></LinearLayout>
</layout></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li></ul>

2、创建ViewHolder时定义一个和item布局 对应的Binding 对象，通过getter和setter对这个Binding对象操作：

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">BindingHolder</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">RecyclerView</span>.<span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">ViewHolder</span> {</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> RecyclerItemBinding binding;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">BindingHolder</span>(View itemView) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>(itemView);}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> RecyclerItemBinding <span class="hljs-title" style="box-sizing: border-box;">getBinding</span>() {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> binding;}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">setBinding</span>(RecyclerItemBinding binding) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.binding = binding;}
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li></ul>

3、在Adapter中onCreateViewHolder()方法中使用DataBindingUtil.inflate()创建Binding 对象，然后创建一个ViewHolder对象，通过ViewHolder的set把Binding对象设置进去：

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">RecyclerItemBinding mItemBinding = DataBindingUtil<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.inflate</span>(LayoutInflater<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.from</span>(mContext), R<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.layout</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.recycler</span>_item, parent, false)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
BindingHolder mHolder = new BindingHolder(mItemBinding<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getRoot</span>())<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
mHolder<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setBinding</span>(mItemBinding)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;//把mItemBinding设置给ViewHolder</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

4、在onBindViewHolder()方法中通过holder的getBinding()方法得到item对应的Binding 对象，再设置数据：

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">//通过holder<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getBinding</span>()得到Binding Class
User user = users<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.get</span>(position)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
holder<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getBinding</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setVariable</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">com</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.sunzxyong</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.binding</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.BR</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.user</span>,user)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
holder<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getBinding</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.executePendingBindings</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;//立即更新UI</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

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好了Data Binding的高级用法就讲完了，下一篇我们通过一个Demo来看看怎么整体使用Data Binding。。。

这篇关于【MVVM】Data Binding高级用法-Observable、动态生成Binding Class（三）的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！

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