步骤
1 放置两张图片ok1和ok2到drawable-mdpi文件夹中

2 在layout文件夹下建立xml文件,如下

<?xml version="1.0" encoding="utf-8"?>
<!-- "@drawable/ok1"表示未点击按钮时的图片 -->
<!-- "@drawable/ok2"表示点击按钮时的图片 -->
<selector xmlns:android="http://schemas.android.com/apk/res/android" >
   <item 
        android:state_pressed="false"
        android:drawable="@drawable/ok1"
   />
   <item 
        android:state_pressed="true"
        android:drawable="@drawable/ok2"
    />
</selector>

3 main.xml文件如下

<?xml version="1.0" encoding="utf-8"?>
<!-- android:background="@layout/ok_selector"图片的背景 -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >
    <ImageButton 
        android:id="@+id/ImageButton1"
        android:background="@layout/ok_selector"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:visibility="visible"
        />
</LinearLayout>