0

我花了一些时间来开发一个程序，显示经过的时间或剩余时间，从用户单击开始按钮开始，就像秒表或计时器一样，它测量时间，直到您停止和重置。测量经过时间的其他示例是赛车游戏中的单圈时间和其他游戏中的时间限制（以毫秒为单位）。

不过，我遇到了一些麻烦，因为我自己的秒表运行速度与实际时间不同。我的计时器向下或向上运行一秒钟需要超过一秒钟的时间。

代码就在这里：（GUI工作得很好；我更关心如何控制值以显示经过的时间，每经过一秒，显示的时间JLabel就会减少一秒。我无法修改传入的参数，Thread.sleep因为它会使计时器变得更糟。）

import javax.swing.*;

import java.awt.event.*;
import java.awt.*;
import java.text.DecimalFormat;
import java.util.concurrent.*;

public class StopwatchGUI3 extends JFrame 
{

    private static final long serialVersionUID = 3545053785228009472L;

    // GUI Components
    private JPanel panel;
    private JLabel timeLabel;

    private JPanel buttonPanel;
    private JButton startButton;
    private JButton resetButton;
    private JButton stopButton;

    // Properties of Program.
    private byte centiseconds = 0;
    private byte seconds = 30;
    private short minutes = 0;

    private Runnable timeTask;
    private Runnable incrementTimeTask;
    private Runnable setTimeTask;
    private DecimalFormat timeFormatter;
    private boolean timerIsRunning = true;

    private ExecutorService executor = Executors.newCachedThreadPool();

    public StopwatchGUI3()
    {
        panel = new JPanel();
        panel.setLayout(new BorderLayout());

        timeLabel = new JLabel();
        timeLabel.setFont(new Font("Consolas", Font.PLAIN, 13));
        timeLabel.setHorizontalAlignment(JLabel.CENTER);
        panel.add(timeLabel);


        buttonPanel = new JPanel();
        buttonPanel.setLayout(new FlowLayout(FlowLayout.CENTER));

        startButton = new JButton("Start");
        startButton.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e)
            {
                if (!timerIsRunning)
                    timerIsRunning = true;

                executor.execute(timeTask);
            }
        });
        buttonPanel.add(startButton);

        resetButton = new JButton("Reset");
        resetButton.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e)
            {
                timerIsRunning = false;

                centiseconds = 0;
                seconds = 30;
                minutes = 0;

                timeLabel.setText(timeFormatter.format(minutes) + ":" 
                        + timeFormatter.format(seconds) + "." 
                        + timeFormatter.format(centiseconds));
            }
        });

        buttonPanel.add(resetButton);

        stopButton = new JButton("Stop");
        stopButton.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e)
            {
                timerIsRunning = false;
            }
        });

        buttonPanel.add(stopButton);


        panel.add(buttonPanel, BorderLayout.SOUTH);


        timeFormatter = new DecimalFormat("00");

        timeTask = new Runnable(){
            public void run()
            {
                while(timerIsRunning)
                {
                    executor.execute(incrementTimeTask);

                    try
                    {
                        Thread.sleep(10);
                    }
                    catch (InterruptedException ex)
                    {
                        ex.printStackTrace();
                    }
                 }
            }
        };

        incrementTimeTask = new Runnable(){
            public void run()
            {
                if (centiseconds > 0)
                    centiseconds--;
                else
                {
                    if (seconds == 0 && minutes == 0)
                        timerIsRunning = false;
                    else if (seconds > 0)
                    {
                        seconds--;
                        centiseconds = 99;
                    }
                    else if (minutes > 0)
                    {
                        minutes--;
                        seconds = 59;
                        centiseconds = 99;
                    }
                }

                executor.execute(setTimeTask);
            }
        };

        setTimeTask = new Runnable(){
            public void run()
            {
                timeLabel.setText(timeFormatter.format(minutes) + ":" 
                        + timeFormatter.format(seconds) + "." 
                        + timeFormatter.format(centiseconds));
            }
        };

        timeLabel.setText(timeFormatter.format(minutes) + ":" 
                + timeFormatter.format(seconds) + "." 
                + timeFormatter.format(centiseconds));

        add(panel);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        setTitle("StopwatchGUI.java");

        pack();
        setVisible(true);
    }

    public static void main(String[] args) 
    {
        new StopwatchGUI3();
    }
}

必须有另一种方法使计时器与实时同步，就像真正的秒表一样，而不必依赖三个单独的线程，我认为这对于如此大型的编程项目来说太多了，但对于入门级来说还可以现在。（哦，顺便说一句，该DecimalFormat课程将像真正的秒表一样正确格式化数字，尽管没有要四舍五入的十进制值。直到现在，在我发布此内容时，才存在一个名为的文本类SimpleDateFormat。）

换句话说，我希望这个程序只是一个真正的秒表。如果不是这种情况，那么如何在 Java 游戏中创建或使用秒表？

4

2 回答 2

4

您将面临的最大问题是能够让各种Runnables 以一致的速度运行。基本上，没有真正的方法可以知道何时Executor实际执行您提供的任务，因为它有自己的开销。

在这种特殊情况下，我建议将活动Threads 的数量减少到一个，这样可以减少创建和执行其他 s 所涉及的任何额外开销，Thread并为您提供最好的控制，让事情尽可能接近您想要的时间尽可能。

Thread我不会使用 a ，而是使用 a , javax.swing.Timerprimary 因为它很简单并且在 EDT 的上下文中执行，这使得从内部更新 UI 更安全，例如

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DecimalFormat;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class StopwatchGUI3 extends JFrame {

    private static final long serialVersionUID = 3545053785228009472L;

    // GUI Components
    private JPanel panel;
    private JLabel timeLabel;

    private JPanel buttonPanel;
    private JButton startButton;
    private JButton resetButton;
    private JButton stopButton;

    // Properties of Program.
    private byte centiseconds = 0;
    private byte seconds = 30;
    private short minutes = 0;

    private DecimalFormat timeFormatter;

    private Timer timer;

    public StopwatchGUI3() {
        panel = new JPanel();
        panel.setLayout(new BorderLayout());

        timeLabel = new JLabel();
        timeLabel.setFont(new Font("Consolas", Font.PLAIN, 13));
        timeLabel.setHorizontalAlignment(JLabel.CENTER);
        panel.add(timeLabel);

        buttonPanel = new JPanel();
        buttonPanel.setLayout(new FlowLayout(FlowLayout.CENTER));

        startButton = new JButton("Start");
        startButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {

                timer.start();

            }
        });
        buttonPanel.add(startButton);

        resetButton = new JButton("Reset");
        resetButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {

                timer.stop();

                centiseconds = 0;
                seconds = 30;
                minutes = 0;

                timeLabel.setText(timeFormatter.format(minutes) + ":"
                        + timeFormatter.format(seconds) + "."
                        + timeFormatter.format(centiseconds));
            }
        });

        buttonPanel.add(resetButton);

        stopButton = new JButton("Stop");
        stopButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                timer.stop();
            }
        });

        buttonPanel.add(stopButton);

        panel.add(buttonPanel, BorderLayout.SOUTH);

        timeFormatter = new DecimalFormat("00");

        timer = new Timer(10, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                if (centiseconds > 0) {
                    centiseconds--;
                } else {
                    if (seconds == 0 && minutes == 0) {
                        timer.stop();
                    } else if (seconds > 0) {
                        seconds--;
                        centiseconds = 99;
                    } else if (minutes > 0) {
                        minutes--;
                        seconds = 59;
                        centiseconds = 99;
                    }
                }
                timeLabel.setText(timeFormatter.format(minutes) + ":"
                        + timeFormatter.format(seconds) + "."
                        + timeFormatter.format(centiseconds));
            }
        });

        timeLabel.setText(timeFormatter.format(minutes) + ":"
                + timeFormatter.format(seconds) + "."
                + timeFormatter.format(centiseconds));

        add(panel);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        setTitle("StopwatchGUI.java");

        pack();
        setVisible(true);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                new StopwatchGUI3();
            }
        });
    }
}

我当时也会停止“猜测”。根本无法保证“更新”之间经过的时间量是准确的。

相反，我会在秒表启动时获取当前时间，并在 的每个刻度上Timer，从当前时间中减去它，给你已经过去的时间量。然后，您可以使用它来确定秒表的当前值应该是什么......

例如...

添加以下实例字段...

private long startTime;
private long runTime = 30000; // 30 seconds...

更新startButton以包括捕获开始时间...

startButton.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {

        startTime = System.currentTimeMillis();
        timer.start();

    }
});

然后更新Timer如下...

timer = new Timer(10, new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {

        long now = System.currentTimeMillis();
        long dif = now - startTime;
        if (dif >= runTime) {

            timer.stop();
            dif = runTime;

        }

        dif = runTime - dif;

        long minutes = dif / (60 * 1000);
        dif = Math.round(dif % (60 * 1000));
        long seconds = dif / 1000;
        dif = Math.round(dif % 1000);
        long centiseconds = dif / 10;

        timeLabel.setText(timeFormatter.format(minutes) + ":"
                + timeFormatter.format(seconds) + "."
                + timeFormatter.format(centiseconds));
    }
});

查看Swing 中的并发以获取更多详细信息

于 2014-01-09T05:13:31.370 回答
2

“必须有另一种方法使计时器与实时同步，就像真正的秒表一样，而不是依赖三个单独的线程，我认为对于这样一个大型编程项目来说太多了，”

你可以只使用一个javax.swing.Timer. 它相当容易使用。基本构造函数如下所示

Timer(int duration, ActionListener listener)

所以你可以做的就是将一个Timer对象声明为类成员。然后在构造函数中，对其进行初始化。像这样的东西

public Constructor() {
    timer = new Timer(1000, new ActionLisentener(){
        public void actionPerformed(ActionEvent e) {
            // do something
        }
    });
}

您可以在计时器中增加一个计数。计时器也有方法stop() start()，restart()您可以使用。

如果你想要一个看起来更干净的构造函数，你总是可以创建一个内部监听器类，比如

private class TimerListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
        // do something
    }
}

然后像这样初始化你的计时器

timer = new Timer(1000, new TimerListener());
于 2014-01-09T05:12:24.143 回答