Handler和ProgressBar实现进度条的开始，暂停，中止，后退和循环

一，涉及的handler类方法

1，

post(Runnable r)

Causes the Runnable r to be added to the message queue.将要执行的线程对象加到队列当中 

2，

removeCallbacks(Runnable r)

Remove any pending posts of Runnable r that are in the message queue.移除队列当中未执行的线程对象

3，

postDelayed(Runnable r, long delayMillis)

Causes the Runnable r to be added to the message queue, to be run after the specified amount of time elapses.

将要执行的线程对象放入到队列当中，待时间结束后，运行制定的线程对象

二，编写程序

程序效果：实现进度条的开始，暂停，中止，后退和循环

主activity

[java]  view plain copy

1. package com.song;  
2.   
3. import android.app.Activity;  
4. import android.os.Bundle;  
5. import android.os.Handler;  
6. import android.view.View;  
7. import android.view.View.OnClickListener;  
8. import android.widget.Button;  
9. import android.widget.ProgressBar;  
10.   
11. public class C93_Handler3Activity extends Activity {  
12.     /** Called when the activity is first created. */  
13.     ProgressBar bar;  
14.     Button start,pause,back,stop;  
15.     Handler handler;  
16.     @Override  
17.     public void onCreate(Bundle savedInstanceState) {  
18.         super.onCreate(savedInstanceState);  
19.         setContentView(R.layout.main);  
20.         handler=new Handler();  
21.         bar=(ProgressBar)findViewById(R.id.bar);  
22.         start=(Button)findViewById(R.id.start);  
23.         pause=(Button)findViewById(R.id.pause);  
24.         back=(Button)findViewById(R.id.back);  
25.         stop=(Button)findViewById(R.id.stop);  
26.         start.setOnClickListener(new OnClickListener() {  
27.               
28.             @Override  
29.             public void onClick(View v) {  
30.                 // TODO Auto-generated method stub  
31.                 //开始按钮，将要执行的线程对象放到队列当中   
32.                 handler.post(runnable);  
33.             }  
34.         });  
35.         pause.setOnClickListener(new OnClickListener() {  
36.               
37.             @Override  
38.             public void onClick(View v) {  
39.                 // TODO Auto-generated method stub  
40.                 //暂停按钮，删除队列当中未执行的线程对象  
41.                 handler.removeCallbacks(runnable);  
42.             }  
43.         });  
44.         back.setOnClickListener(new OnClickListener() {  
45.               
46.             @Override  
47.             public void onClick(View v) {  
48.                 // TODO Auto-generated method stub  
49.                 if(prolength!=0)  
50.                 {  
51.                     prolength=bar.getProgress()-1;  
52.                     bar.setProgress(prolength);  
53.                     setTitle(String.valueOf(prolength));  
54.                 }  
55.             }  
56.         });  
57.         stop.setOnClickListener(new OnClickListener() {  
58.               
59.             @Override  
60.             public void onClick(View v) {  
61.                 // TODO Auto-generated method stub  
62.                 handler.removeCallbacks(runnable);  
63.                 bar.setProgress(0);  
64.                 setTitle(String.valueOf(0));  
65.             }  
66.         });  
67.           
68.     }  
69.     int prolength=0;//定义进程度  
70.     //定义线程  
71.     Runnable runnable=new Runnable() {  
72.           
73.         @Override  
74.         public void run() {  
75.             // TODO Auto-generated method stub  
76.             prolength=bar.getProgress()+1;  
77.             bar.setProgress(prolength);  
78.             setTitle(String.valueOf(prolength));  
79.             //若是进度小于100,则延迟1000毫秒以后重复执行runnable  
80.             if(prolength<100)  
81.             {  
82.                 handler.postDelayed(runnable, 1000);  
83.             }  
84.             //不然，都置零，线程从新执行  
85.             else   
86.             {  
87.                 bar.setProgress(0);  
88.                 setTitle(String.valueOf(0));  
89.                 handler.post(runnable);  
90.             }  
91.         }  
92.     };  
93. }  

布局文件

[html]  view plain copy

1. <?xml version="1.0" encoding="utf-8"?>  
2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
3.     android:layout_width="fill_parent"  
4.     android:layout_height="fill_parent"  
5.     android:orientation="vertical" >  
6.   
7.    <ProgressBar android:layout_width="fill_parent"  
8.        android:layout_height="wrap_content"  
9.        android:id="@+id/bar"  
10.        style="@android :style/Widget.ProgressBar.Horizontal"  
11.        />  
12.    <LinearLayout android:layout_width="fill_parent"  
13.        android:layout_height="fill_parent"  
14.        android:orientation="horizontal">  
15.        <Button android:layout_width="wrap_content"  
16.        android:layout_height="wrap_content"  
17.        android:layout_weight="2"  
18.        android:id="@+id/start"  
19.        android:text="开始"/>  
20.        <Button android:layout_width="wrap_content"  
21.        android:layout_height="wrap_content"  
22.        android:layout_weight="2"  
23.        android:id="@+id/pause"  
24.        android:text="暂停"/>  
25.        <Button android:layout_width="wrap_content"  
26.        android:layout_height="wrap_content"  
27.        android:layout_weight="2"  
28.        android:id="@+id/back"  
29.        android:text="后退"/>  
30.        <Button android:layout_width="wrap_content"  
31.            android:layout_height="wrap_content"  
32.            android:layout_weight="2"  
33.            android:id="@+id/stop"  
34.            android:text="中止"/>  
35.    </LinearLayout>  
36.       
37.   
38. </LinearLayout>  

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