1. <ProgressBar
2.         android:id="@+id/pb"
3.         style="@android:style/Widget.ProgressBar.Horizontal"
4.         android:layout_width="match_parent"
5.         android:layout_height="wrap_content"
6.         android:layout_marginBottom="6dp"
7.         android:layout_marginTop="6dp"
8.         android:minHeight="0dp"
9.         android:progressDrawable="@drawable/progress_horizontal"/>

1. <?xmlversion="1.0"encoding="utf-8"?>
2. <layer-listxmlns:android="http://schemas.android.com/apk/res/android"
   >
3.     <item
4.         android:id="@android:id/background"
5.         android:drawable="@drawable/cloudsync_notice_progressbar_0percent">
6.     </item>
7.     <itemandroid:id="@android:id/secondaryProgress">
8.         <scale
9.             android:drawable="@drawable/progressbar_0percent"
10.             android:scaleWidth
    ="100%"/>
11.     </item>
12.     <itemandroid:id="@android:id/progress">
13.         <scale
14.             android:drawable="@drawable/progressbar_percent"
15.             android:scaleWidth="100%"/>
16.     </item>
17. </layer-list>

注意：secondaryProgress和progress兩個專案使用自定義drawable時要使用<scale/>子項，否則進度條會一直顯示滿的狀態。

轉自：http://blog.csdn.net/javensun/article/details/16946187