从 5 到 0 的摇摆倒计时

Question

我正在创建一个 Java Swing 游戏，并且在每个新游戏之前，我都希望有一个帧显示和从 5 秒到 0 秒的倒计时。

在发生这种情况时，我希望后台游戏等到倒计时完成。让游戏在后台等待的最佳方法是什么？

我已经尝试过 Thread.sleep 但这会导致事件调度线程进入睡眠状态并且 GUI 不会更新。但是，它在我第一次运行时有效，但在第二次时无效。

感谢您的帮助。

public class CountdownPresenterPanel {
    JFrame mainFrame;
    int currentNumber = 5;
    JLabel textLabel;

    CountdownPresenterPanel() {
        mainFrame = new JFrame();
        textLabel = new JLabel(String.valueOf(currentNumber), SwingConstants.CENTER);
        textLabel.setFont(new Font("Arial", Font.BOLD, 55));
        textLabel.setVerticalAlignment(SwingConstants.CENTER);
        mainFrame.add(textLabel);
        mainFrame.setUndecorated(true); // Remove bar including close, minimize
        mainFrame.setSize(600,300);
        mainFrame.setLocationRelativeTo(null);
        mainFrame.setVisible(true);
        Timer timer = new Timer(1000, new ActionListener() { 
            @Override
            public void actionPerformed(ActionEvent e) {
                if(currentNumber > 0) {
                    currentNumber--;
                    textLabel.setText(String.valueOf(currentNumber));
                } else {
                    mainFrame.setVisible(false);
                    mainFrame.dispose();
                }
            }
        });
        timer.setRepeats(true);
        timer.start();
    }
}

解决方案

import java.awt.*;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.SwingConstants;
import javax.swing.Timer;

public class CountdownPresenterPanel {
    private int currentNumber = 5;
    private JLabel textLabel;
    private final JDialog dialog;
    CountdownPresenterPanel() {
        Timer timer = new Timer(1000, new ActionListener() { 
            @Override
            public void actionPerformed(ActionEvent e) {
                if(currentNumber > 0) {
                    currentNumber--;
                    textLabel.setText(String.valueOf(currentNumber));
                } else {
                    dialog.dispose();
                }
            }
        });
        Frame window = new Frame();
        dialog = new JDialog(window, "Alert", true);
        textLabel = new JLabel(String.valueOf(currentNumber), SwingConstants.CENTER);
        textLabel.setFont(new Font("Arial", Font.BOLD, 55)); // Increase the font-size
        dialog.add(textLabel);
        dialog.setSize(400, 200);
        dialog.setLocationRelativeTo(null);
        timer.setRepeats(true);
        timer.start();
        dialog.setUndecorated(true);
        dialog.setVisible(true);
    }
}

Answer 1

不要使用JFrame，使用某种模式对话框

查看How to Make Dialogs了解更多详情

Answer 2

您似乎想要SplashScreen之类的东西。你看过SplasScreen Tutorial from Oracle? 那里Thread.sleep() 是安全使用的，它会正确更新图形。我认为这是您独特的解决方案。让正在进行的应用程序等待的唯一方法是使用相同的线程。您的 Timer 不起作用的原因是它创建了另一个线程来运行自己。

Answer 3

另一种选择是使用SwingWorker：

import java.awt.*;
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.beans.*;
import javax.swing.*;

public class CountdownPresenterPanel2 {
  public static void main(String[] args) {
    final JFrame frame = new JFrame();
    final JDialog splashScreen = new JDialog(null, Dialog.ModalityType.DOCUMENT_MODAL);
    final JLabel textLabel = new JLabel(String.valueOf(5), SwingConstants.CENTER);

    EventQueue.invokeLater(new Runnable() {
      @Override public void run() {
        textLabel.setFont(new Font("Arial", Font.BOLD, 55));
        textLabel.setVerticalAlignment(SwingConstants.CENTER);
        splashScreen.setUndecorated(true);
        splashScreen.getContentPane().add(textLabel);
        splashScreen.setSize(600, 300);
        splashScreen.setLocationRelativeTo(null);
        splashScreen.setVisible(true);
      }
    });
    (new GamePanelInitTask() {
      @Override protected void process(java.util.List<Integer> chunks) {
        for (Integer value : chunks) {
          textLabel.setText(value.toString());
        }
      }
      @Override public void done() {
        splashScreen.dispose();
        try {
          MainGamePanel p = get();
          frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
          frame.getContentPane().add(p);
          frame.setSize(320, 240);
          frame.setLocationRelativeTo(null);
          frame.setVisible(true);
        } catch (InterruptedException | ExecutionException ex) {
          ex.printStackTrace();
        }
      }
    }).execute();
  }
}

class GamePanelInitTask extends SwingWorker<MainGamePanel, Integer> {
  @Override public MainGamePanel doInBackground() {
    int currentNumber = 5;
    MainGamePanel game = new MainGamePanel();
    while (currentNumber > 0 && !isCancelled()) {
      currentNumber--;
      publish(currentNumber);
      game.add(new JLabel(String.format("Label: %d", currentNumber)));
      try {
        Thread.sleep(1000); //dummy task
      } catch (InterruptedException ie) {
        ie.printStackTrace();
        return null;
      }
    }
    return game;
  }
}

class MainGamePanel extends JPanel {
  public MainGamePanel() {
    super();
    try {
      Thread.sleep(1000); //dummy task
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
  }
}