android Button 颜色的变化（点击，放开，点击不放）

参考：

http://endual.iteye.com/blog/1534258

总结：

定义res/drawable/button_style.xml文件

<?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/play_press" />
	<item android:state_focused="true" android:drawable="@drawable/play_press" />
	<item android:drawable="@drawable/play" />
</selector>

以上需要放两种图片，play_press.png和play.png

也可以直接使用颜色：

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

  使用style文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:orientation="vertical" android:layout_width="fill_parent"
	android:layout_height="fill_parent">
	<TextView android:layout_width="fill_parent"
		android:layout_height="wrap_content" android:text="@string/hello" />
	<Button android:id="@+id/button1"
		android:layout_width="wrap_content" android:layout_height="wrap_content"
		android:background="@drawable/button_style"
		></Button>
</LinearLayout>