Android 按钮按下效果

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android" >
    
 <item android:state_pressed="true" android:drawable="@drawable/bus_s" />
 
<item android:state_pressed="false" android:state_focused="false"
  android:drawable="@drawable/bus_u" />

<item android:state_focused="true" android:drawable="@drawable/bus_s" />

<item android:state_focused="false" android:drawable="@drawable/bus_u" />

<item android:state_checked="true" android:drawable="@drawable/bus_s"></item>

</selector>

 2./res/layout/team_unit_view.xml
 <?xml version="1.0" encoding="utf-8"?>
 <Button
     android:layout_width="400dp"
     android:layout_height="135dp"
     android:background="@drawable/selector"
     android:orientation="horizontal" >
 </button>