selector + drawable 多状态图形

select_drawble.xml
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <!-- 按下的图片 (必须写在前面)-->
    <item android:state_pressed="true" android:drawable="@drawable/main_index_search_pressed"></item>
    <!-- 正常情况下的图片 -->
    <item android:drawable="@drawable/main_index_search_normal"></item>

</selector>

    <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:background="@drawable/select_drawble"
            android:onClick="clickIV" />