Android-《第一行代码》阅读收获

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1.如何隐藏标题栏

requestWindowFeature(Window.FEATURE_NO_TITLE);

2.自定义Toast

最基础的Toast

Context context = getApplicationContext();
CharSequence text = "Hello toast!";
int duration = Toast.LENGTH_SHORT;Toast toast = Toast.makeText(context, text, duration);
toast.show();

toast.setGravity(Gravity.TOP|Gravity.LEFT, 0, 0);

可以设置Toast的显示位置差数的意义 a Gravity constant, an x-position offset, and a y-position offset.

那么到该怎么

Creating a Custom Toast View

首先写一个xml( toast_layout.xml)

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:id="@+id/toast_layout_root"android:orientation="horizontal"android:layout_width="fill_parent"android:layout_height="fill_parent"android:padding="8dp"android:background="#DAAA"><ImageView android:src="@drawable/droid"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_marginRight="8dp"/><TextView android:id="@+id/text"android:layout_width="wrap_content"android:layout_height="wrap_content"android:textColor="#FFF"/>
</LinearLayout>

然后通过setView方法

LayoutInflater inflater = getLayoutInflater();
View layout = inflater.inflate(R.layout.custom_toast,(ViewGroup) findViewById(R.id.toast_layout_root));TextView text = (TextView) layout.findViewById(R.id.text);
text.setText("This is a custom toast");Toast toast = new Toast(getApplicationContext());
toast.setGravity(Gravity.CENTER_VERTICAL, 0, 0);
toast.setDuration(Toast.LENGTH_LONG);
toast.setView(layout);
toast.show();

就是这么简单

3.Menu

分为3类

Options menu and action bar 选项菜单

Context menu and contextual action mode 上下文菜单当长时间点击某些东西的时候响应

Popup menu 弹出菜单

首先是编写main.xml menu标签如：

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"><item android:id="@+id/new_game"android:icon="@drawable/ic_new_game"android:title="@string/new_game"android:showAsAction="ifRoom"/><item android:id="@+id/help"android:icon="@drawable/ic_help"android:title="@string/help" />
</menu>

其中 showAsAction的解析是

android:showAsAction

Specifies when and how this item should appear as an action item in the action bar.

下面是这些属性的具体语法：

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"><item android:id="@[+][package:]id/resource_name"android:title="string"android:titleCondensed="string"android:icon="@[package:]drawable/drawable_resource_name"android:onClick="method name"android:showAsAction=["ifRoom" | "never" | "withText" | "always" | "collapseActionView"]android:actionLayout="@[package:]layout/layout_resource_name"android:actionViewClass="class name"android:actionProviderClass="class name"android:alphabeticShortcut="string"android:numericShortcut="string"android:checkable=["true" | "false"]android:visible=["true" | "false"]android:enabled=["true" | "false"]android:menuCategory=["container" | "system" | "secondary" | "alternative"]android:orderInCategory="integer" /><group android:id="@[+][package:]id/resource name"android:checkableBehavior=["none" | "all" | "single"]android:visible=["true" | "false"]android:enabled=["true" | "false"]android:menuCategory=["container" | "system" | "secondary" | "alternative"]android:orderInCategory="integer" ><item /></group><item ><menu><item /></menu></item>
</menu>

下面就来看看如何使用吧

首先你得知道2.3之前和和3.0之后的选项菜单是不一样的 2.3是在底部弹出 3.0是在actionBar那里是不一样的

重写方法

onCreateOptionsMenu

@Override
public boolean onCreateOptionsMenu(Menu menu) {MenuInflater inflater = getMenuInflater();inflater.inflate(R.menu.game_menu, menu);return true;
}

在onOptionsItemSelected里面响应事件

@Override
public boolean onOptionsItemSelected(MenuItem item) {// Handle item selectionswitch (item.getItemId()) {case R.id.new_game:newGame();return true;case R.id.help:showHelp();return true;default:return super.onOptionsItemSelected(item);}
}