安卓用代码来实现selector

本文主要是介绍安卓用代码来实现selector，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！

android可以通过XML文件来创建selector，以Drawable对象的形式安装到组件上，以提供统一的风格设置。但是在某些时候，我们需要通过代码的形式来实现相同的功能，例如组件数量非常多，对应不同的图片，这时候如果还用XML的话就需要创建大量的selector文件，非常繁琐。

例如一个TextView使用了如下的selector

 < TextView 
          android:id = "@+id/TextView_title" 
          android:layout_width = "wrap_content" 
          android:layout_height = "wrap_content" 
          android:focusable = "true" 
          android:drawableTop = "@drawable/selector_tabwidget_icon" 
          android:textAlignment = "center" 
          /> 

 <? xml  version = "1.0"  encoding = "utf-8" ?> 
 < selector  xmlns:android = "http://schemas.android.com/apk/res/android"  > 
      <!-- Non focused states --> 
      < item  android:state_focused = "false"  android:state_selected = "false"  android:state_pressed = "false"  android:drawable = "@drawable/contact"  /> 
      < item  android:state_focused = "false"  android:state_selected = "true"  android:state_pressed = "false"  android:drawable = "@drawable/contact_sel"  /> 
      <!-- Focused states --> 
      < item  android:state_focused = "true"  android:state_selected = "false"  android:state_pressed = "false"  android:drawable = "@drawable/contact_sel"  /> 
      < item  android:state_focused = "true"  android:state_selected = "true"  android:state_pressed = "false"  android:drawable = "@drawable/contact_sel"  /> 
      <!-- Pressed --> 
      < item  android:state_selected = "true"  android:state_pressed = "true"  android:drawable = "@drawable/contact_sel"  /> 
      < item  android:state_pressed = "true"  android:drawable = "@drawable/contact_sel"  /> 
 </ selector > 

里面所引用的图片资源文件非常多，如果每个文件都对应一个XML的文件的话，就会非常繁琐，修改起来非常麻烦。

　　实际上，所有XML设定能做的事情，android里同样可以用编码的方式来实现，像上面那个XML文件，就可以就下面的代码来实现：

 StateListDrawable drawable =  new  StateListDrawable(); 
          //Non focused states 
          drawable.addState( new  int []{-android.R.attr.state_focused, -android.R.attr.state_selected, -android.R.attr.state_pressed}, 
                  getResources().getDrawable(R.drawable.contact)); 
          drawable.addState( new  int []{-android.R.attr.state_focused, android.R.attr.state_selected, -android.R.attr.state_pressed}, 
                  getResources().getDrawable(R.drawable.contact_sel)); 
          //Focused states 
          drawable.addState( new  int []{android.R.attr.state_focused,-android.R.attr.state_selected, -android.R.attr.state_pressed}, 
                  getResources().getDrawable(R.drawable.contact_sel)); 
          drawable.addState( new  int []{android.R.attr.state_focused,android.R.attr.state_selected, -android.R.attr.state_pressed}, 
                  getResources().getDrawable(R.drawable.contact_sel)); 
          //Pressed 
          drawable.addState( new  int []{android.R.attr.state_selected, android.R.attr.state_pressed}, 
                  getResources().getDrawable(R.drawable.contact_sel)); 
          drawable.addState( new  int []{android.R.attr.state_pressed}, 
                  getResources().getDrawable(R.drawable.contact_sel)); 
            
          TextView textView = (TextView) findViewById(R.id.TextView_title); 
                   
          textView.setCompoundDrawablesWithIntrinsicBounds( null , drawable,  null ,  null ); 