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

package com.song;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;

public class C93_Handler3Activity extends Activity {
/** Called when the activity is first created. */
ProgressBar bar;
Button start,pause,back,stop;
Handler handler;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
handler=new Handler();
bar=(ProgressBar)findViewById(R.id.bar);
start=(Button)findViewById(R.id.start);
pause=(Button)findViewById(R.id.pause);
back=(Button)findViewById(R.id.back);
stop=(Button)findViewById(R.id.stop);
start.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
//开始按钮，将要执行的线程对象放到队列当中
handler.post(runnable);
}
});
pause.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
//暂停按钮，删除队列当中未执行的线程对象
handler.removeCallbacks(runnable);
}
});
back.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if(prolength!=0)
{
prolength=bar.getProgress()-1;
bar.setProgress(prolength);
setTitle(String.valueOf(prolength));
}
}
});
stop.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
handler.removeCallbacks(runnable);
bar.setProgress(0);
setTitle(String.valueOf(0));
}
});

}
int prolength=0;//定义进程度
//定义线程
Runnable runnable=new Runnable() {

@Override
public void run() {
// TODO Auto-generated method stub
prolength=bar.getProgress()+1;
bar.setProgress(prolength);
setTitle(String.valueOf(prolength));
//如果进度小于100,则延迟1000毫秒之后重复执行runnable
if(prolength<100)
{
handler.postDelayed(runnable, 1000);
}
//否则，都置零，线程重新执行
else
{
bar.setProgress(0);
setTitle(String.valueOf(0));
handler.post(runnable);
}
}
};
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<ProgressBar android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="@+id/bar"
style="@android:style/Widget.ProgressBar.Horizontal"
/>
<LinearLayout android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal">
<Button android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="2"
android:id="@+id/start"
android:text="开始"/>
<Button android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="2"
android:id="@+id/pause"
android:text="暂停"/>
<Button android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="2"
android:id="@+id/back"
android:text="后退"/>
<Button android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="2"
android:id="@+id/stop"
android:text="停止"/>
</LinearLayout>

</LinearLayout>