android背景设置报错 <item> tag requires a 'drawable' attribute or child tag defining a drawable<转>

android背景设置报错 tag requires a ‘drawable’ attribute or child tag defining a drawable<转>
今天本来只是想实现一个简单的按下ImageButton背景变颜色的功能，结果碰到 tag requires a ‘drawable’ attribute or child tag defining a drawable的错误。这句话的意思很简单，就是说item标签下需要drawable属性。在逛了无数国内论坛无果后，我尝试进了一个英文网站，结果如醍醐灌顶，深深的感觉到国内和国外的差距。
The problem here is that you cannot define the background color using a color selector, you need a drawable selector. So, the necessary changes would look like this:
你不能将颜色选择器用在background上，应该使用drawable selector，所以你应该这样修改(假设文件名为selector.xml)：<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item
android:state_pressed="true"
android:drawable="@drawable/selected_state" />
</selector>awable/selected_state"/>
</selector>
You would also need to move that resource to the drawable directory where it would make more sense since it’s not a color selector per se.
Then you would have to create the res/drawable/selected_state.xml file like this:
同时你也要将selected_state.xml放在drawable目录下而不是color目录，然后这样定义res/drawable/selected_state.xml：

<?xml version="1.0" encoding="UTF-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android"    android:shape="rectangle">    <solid android:color="@color/semitransparent_white" /></shape>

and finally, you would use it like this:
最后在imageView中我们这样定义background：
android:background=”@drawable/selector”
其实这种方法将selector和颜色的定义分开了 我们可以将selector和shape的定义放在一起：

<selector xmlns:android="http://schemas.android.com/apk/res/android">    <item android:state_pressed="true">        <shape>            <solid android:color="#F1F1F1"/>        </shape>    </item>    <item android:state_selected="true">        <shape>            <solid android:color="#F1F1F1"/>        </shape>               </item></selector>