关于selector的有关问题

关于selector的问题
问什么selector没有出现效果？求大神 啊


调用的时候：android:background="@drawable/selector"

HTML code

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

[解决办法]
没效果是只显示tab_btn_bg_f这张还是tab_btn_bg这张？

写这么复杂真心用的着么？
[解决办法]
使用的不对吧
[解决办法]
最简单的，
<?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/spinner_dropdown_pressed" /> 
<item android:state_focused="true" android:drawable="@drawable/spinner_dropdown_pressed" /> 
<item android:drawable="@drawable/spinner_dropdown_normal" /> 
</selector>
这样试试