点击图片缩小放开又弹回来的效果

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="true">
        <layer-list>
            <item android:drawable="@drawable/test"
                android:top="3dp"
                android:bottom="3dp"
                android:left="3dp"
                android:right="3dp"/>
        </layer-list>
    </item>
    <item android:drawable="@drawable/test" />
</selector>