Android实现带有进度条的按钮效果

<relativelayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:paddingbottom="@dimen/activity_vertical_margin"
    android:paddingleft="@dimen/activity_horizontal_margin"
    android:paddingright="@dimen/activity_horizontal_margin"
    android:paddingtop="@dimen/activity_vertical_margin"
    tools:context=".mainactivity" >
 
   <textview
     android:id="@+id/text"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:text="带有进度条的button" />
 
   <relativelayout
     android:layout_width="fill_parent"
     android:layout_height="50dp"
     android:layout_centerhorizontal="true"
     android:layout_centervertical="true"
     android:gravity="bottom" >
 
     <progressbar
       android:id="@+id/progressbar"
       style="?android:attr/progressbarstylehorizontal"
       android:layout_width="fill_parent"
       android:layout_height="fill_parent"
       android:background="@drawable/aa_button_gray_normal"
       android:max="100"
       android:progress="0"
       android:progressdrawable="@drawable/progress_selector" />
 
     <button
       android:id="@+id/downloadbtn"
       android:layout_width="fill_parent"
       android:layout_height="fill_parent"
       android:layout_centerhorizontal="true"
       android:layout_centervertical="true"
       android:background="@drawable/btn_selector"
       android:text="下载" />
   </relativelayout>
 
</relativelayout>

package com.example.buttondemo;
 
import android.app.activity;
import android.os.bundle;
import android.os.handler;
import android.os.message;
import android.view.view;
import android.widget.button;
import android.widget.progressbar;
import android.widget.textview;
 
 public class mainactivity extends activity {
   int i = 0;
   progressbar progressbar = null;
   button downloadbtn = null;
   handler handler = new handler() {
     public void handlemessage(android.os.message msg) {
       switch (msg.what) {
       case 1:
         i += 5;
         progressbar.setprogress(i);
         if (i != 100) {
           handler.sendemptymessagedelayed(new message().what = 1, 500);
           downloadbtn.settext(i + "%");
         } else if (i == 100) {
           downloadbtn.settext("下载完成");
           // 进度条运行完成时按钮可用
           downloadbtn.setenabled(true);
         }
         break;
 
       default:
         break;
       }
     };
   };
 
   @override
   protected void oncreate(bundle savedinstancestate) {
     super.oncreate(savedinstancestate);
     setcontentview(r.layout.activity_main);
     textview tx = (textview) findviewbyid(r.id.text);
     progressbar = (progressbar) findviewbyid(r.id.progressbar);
     downloadbtn = (button) findviewbyid(r.id.downloadbtn);
     downloadbtn.setonclicklistener(new view.onclicklistener() {
 
       @override
       public void onclick(view v) {
         i = 0;
         handler.sendemptymessage(new message().what = 1);
         // 进度条运行时按钮不可用
         downloadbtn.setenabled(false);
       }
     });
   }
 
}