如何为Java游戏小程序设置两个定时器

Question

我需要两个定时器。一个用来运行游戏，比如移动对象，执行检查，另一个作为倒数计时器。我尝试了以下几点：

Timer countdownTimer = new Timer(1000,this);
Timer gameTimer = new Timer(30,this);

public void init()
{
   this.actionPerformed(this); //add action listener to content pane
}

@Override
public void actionPerformed(ActionEvent e) 
{
    if(e.getSource() == gameTimer)
    {
        // control the game
    }

    if(e.getSource() == countdownTimer)
    {
       //decremenet the timer
    }
}

但是，当我试图运行applet时，这会返回一个空指针异常。如何正确区分每个定时器和另一个计时器，并在每个计时器滴答时执行所需的操作。谢谢

Answer 1

我假设您使用的是javax.swing.Timer类？this.actionPerformed(this);似乎不正确，因为您的applet不是ActionEvent。此外，您应该在init()方法中启动定时器：

public class GameApplet extends Appel implements ActionListener
    public void init()
    {
        countdownTimer = new Timer(1000,this);
        gameTimer = new Timer(30,this);
        countdownTimer.start();
        gameTimer.start();
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        if(e.getSource() == gameTimer) {
            // control the game
        }

        if(e.getSource() == countdownTimer) {
           //decremenet the timer
        }
    }
}

检查同样重定向到计时器javadoc的关于计时器的Java教程。

Answer 2

使用ScheduledExecutorService。它比计时器更有效率。若要查看其效果，请运行以下代码。

class GameControl {
    private final ScheduledExecutorService scheduler =
            Executors.newScheduledThreadPool(1);

    public void beepForGame() {
        final Runnable beeper = new Runnable() {
            @Override
            public void run() {
                System.out.println("Game");
            }
        };
        final ScheduledFuture<?> beeperHandle =
                scheduler.scheduleAtFixedRate(beeper, 30, 30, SECONDS);
        scheduler.schedule(new Runnable() {
            @Override
            public void run() {
                beeperHandle.cancel(true);
            }
        }, 60 * 60, SECONDS);
    }

    public void beepCountDown() {
        final Runnable beeper = new Runnable() {
            @Override
            public void run() {
                System.out.println("count down");
            }
        };
        final ScheduledFuture<?> beeperHandle =
                scheduler.scheduleAtFixedRate(beeper, 1, 1, SECONDS);
        scheduler.schedule(new Runnable() {
            @Override
            public void run() {
                beeperHandle.cancel(true);
            }
        }, 60 * 60, SECONDS);
    }
    public static void main(String[] args) {
        GameControl bc=new GameControl();
        bc.beepCountDown();
        bc.beepForGame();
    }
}