Android: 押されるとカクッと画像の角度が変わるボタン

button_stateful.xml

<?xml version="1.0" encoding="utf-8" ?>  
<selector xmlns:android="http://schemas.android.com/apk/res/android">  
    <item android:state_pressed="true">
	    <rotate 
	        android:fromDegrees="10"
	        android:toDegrees="10"
	        android:pivotX="50%"
	        android:pivotY="50%"
	        android:drawable="@drawable/ic_launcher" />
    </item>  

    <item android:state_pressed="false">  
	    <bitmap android:src="@drawable/ic_launcher" android:antialias="true" />
	</item>  
</selector>