progressBar的样式

<?xml version="1.0" encoding="utf-8"?><layer-list xmlns:android="http://schemas.android.com/apk/res/android" >    <item android:id="@android:id/background"  android:drawable="@drawable/security_progress_bg"></item>    <item android:id="@android:id/secondaryProgress"  android:drawable="@drawable/security_progress"></item>    <item android:id="@android:id/progress"  android:drawable="@drawable/security_progress"></item></layer-list>