android Button 颜色的变化（点击，放开，点击不放）

<?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>

<?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>

<?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>