安卓Selector详细介绍

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="https://schemas.android.com/apk/res/android" >
    <!-- 默许情形,item必需放在最后 -->
    
    <!-- 非触摸模式下取得焦点并单击时的背景图片 -->
    <item 
        android:state_focused="true"
        android:state_pressed="true"
        android:drawable="@drawable/ic_launcher"
        />
    <!-- 触摸模式下单击时的背景图片-->
    <item 
        android:state_focused="false"
        android:state_pressed="true"
        android:drawable="@drawable/ic_launcher"
        />
    <!--选中时的图片背景-->
    <item 
        android:state_selected="true"
        android:drawable="@drawable/ic_launcher"
        />
    <!--取得焦点时的图片背景-->
    <item 
        android:state_focused="true"
        android:drawable="@drawable/ic_launcher"
        />
    <item 
        android:drawable="@drawable/button_bg_default"
        />
</selector><?xml version="1.0" encoding="utf-8"?>
<selector x