suspendresum.java

SuspendResum为用java线程实现的定时器势力.

import java.awt.*;
import java.awt.event.*;
import java.applet.*;

class Suspender extends Thread
{
	private int count=0;
	private TextField t=new TextField(30);
	
	public Suspender(Container c)
	{
		c.add(t);
	}
	
	public void run()
	{
		while(true)
		{
			t.setText("count="+(count++));
			try
			{
				sleep(100);
			}catch(InterruptedException e){}
		}
	}
}

public class SuspendResum extends Applet
{
	private Button
		start=new Button("Start"),
		suspend=new Button("Suspend"),
		resume=new Button("Ressume");
	private boolean started=false;
	private boolean suspended=false;   //暂停标志
	private Suspender s1=new Suspender(this);
	public void init()
	{
		start.addActionListener(new StartL());
		add(start);
		suspend.addActionListener(new SuspendL());
		add(suspend);
		resume.addActionListener(new ResumeL());
		add(resume);
	}
	
	class StartL implements ActionListener
	{
		//添加Start按钮事件
		public void actionPerformed(ActionEvent e)
		{
			if(!started)
			{
				//线程启动后将标志位started置为true,使"Start"按钮
				//被多次单击时也只会创建一个进程
				started=true;
				s1.start();
			}
		}
	}
	class SuspendL implements ActionListener
	{
		//添加Suspend按钮事件
		public void actionPerformed(ActionEvent e)
		{
			//如果没有被暂停则调用suspend()方法暂停进程
			if(!suspended)
			{
				suspended=true;
				s1.suspend();    //调用suspend（）方法暂停进程
			}
		}
	}
	class ResumeL implements ActionListener
	{
		public void actionPerformed(ActionEvent e)
		{
			//如果线程已被暂停则调用resume（）方法恢复执行
			if(suspended)
			{
				suspended=false;
				s1.resume();  //调用resume()方法恢复执行
			}
		}
	}
	public static void main(String[] arg)
	{
		SuspendResum applet=new SuspendResum();
		Frame aFrame=new Frame("Suspender");
		aFrame.addWindowFocusListener(
			new WindowAdapter()
			{
				public void windowClosing(WindowEvent e)
				{
					System.exit(0);
				}
			});
			aFrame.add(applet,BorderLayout.CENTER);
			aFrame.setSize(250,150);
			applet.init();
			applet.start();
			aFrame.setVisible(true);
	}
}