android小功能：checkbox使用自己的背景点击切换背景

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android" >
<item android:state_selected="true"  android:drawable="@drawable/hookicon_repost_pressed"></item>
<item android:state_checked="true" android:drawable="@drawable/hookicon_repost_pressed"></item>
<item android:state_pressed="true" android:drawable="@drawable/hookicon_repost_pressed"></item>
<item android:drawable="@drawable/ic_checkbox_normal"></item>
</selector>

<CheckBox
android:id="@+id/xiazai_checkbox"
android:layout_width="25dp"
android:layout_height="25dp"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:layout_marginRight="30dp"
android:layout_marginTop="10dp"
android:button="@null"
android:background="@drawable/xiazai_checkbox"
/>