java - Swing 中的同步

Question

有什么方法可以使事件调度线程与 swing.Timer、SwingWorker 或 new Thread() 创建的另一个线程同步？我希望 EDT 等待另一个线程工作(例如在屏幕上移动对象)并在完成此工作后立即执行一些任务。是否可以？我必须使用另一个线程，因为如果我尝试在 EDT 中更改对象的坐标，我在屏幕上看不到运动。

Answer 1

您不想在 EDT 上同步或让它加入其他线程，因为这可能会卡住您的程序。最好的办法可能是使用监听器类型的结构来通知 Swing 代码后台线程已完成，例如可以通过将 PropertyChangeListener 添加到 SwingWorker 并监听“state”属性更改为 SwingWorker.StateValue.DONE。如果您确实使用了它，请务必在您的 PropertyChangeListener 中调用您的 SwingWorker 上的 get() 以捕获所有可能已发生的异常从后台线程中抛出。

For example

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编辑
您在评论中声明:

But I'll try to explain. User presses the button. I want some JPanel object to continuously move to another place on screen as a result of button press. This movement will take about 0.4 seconds and I really don't want any button to respond during this time. Movement is provided by coordinates change + Thread.sleep(5). Seems it's impossible to realize this movement in Event Dispatch Thread. Am I right?

1. 是的，如果您使用 Swing Timer，则很有可能在 EDT 上进行运动。 Swing 计时器使用后台线程在幕后 重复调用其 ActionListener 的 actionPerformed 方法，但有延迟。使用它的关键是它的 actionPerformed 方法中的所有代码都在 EDT 上调用。
2. 如果您想停用按钮，则通过调用 setEnabled(false) 将按钮设置为禁用 1(或更好，它是 Action)。动画完成后撤消此操作。

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例如:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;

import javax.swing.*;

public class MoveBall extends JPanel {
   private static final int PREF_W = 800;
   private static final int PREF_H = PREF_W;
   private static final int BALL_W = 40;
   private static final int BALL_H = BALL_W;
   private static final Color BALL_COLOR = Color.red;
   public static final int TIMER_DELAY = 20;
   private int ballX = BALL_W / 2;
   private int ballY = BALL_H / 2;
   private BufferedImage ballImg;
   private ButtonAction buttonAction = new ButtonAction("Start Animation");
   private Timer timer;

   public MoveBall() {
      ballImg = new BufferedImage(BALL_W, BALL_H, BufferedImage.TYPE_INT_ARGB);
      Graphics2D g2 = ballImg.createGraphics();
      g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);
      g2.setColor(BALL_COLOR);
      g2.fillOval(1, 1, BALL_W - 2, BALL_H - 2);
      g2.dispose();

      add(new JButton(buttonAction));
   }

   @Override
   protected void paintComponent(Graphics g) {
      super.paintComponent(g);
      if (ballImg != null) {
         int x = ballX - BALL_W / 2;
         int y = ballY - BALL_H / 2;
         g.drawImage(ballImg, x, y, null);
      }
   }

   @Override
   public Dimension getPreferredSize() {
      if (isPreferredSizeSet()) {
         return super.getPreferredSize();
      }
      return new Dimension(PREF_W, PREF_H);
   }

   private class ButtonAction extends AbstractAction {
      public ButtonAction(String name) {
         super(name);
         int mnemonic = (int)name.charAt(0);
         putValue(MNEMONIC_KEY, mnemonic);
      }

      @Override
      public void actionPerformed(ActionEvent e) {
         ballX = BALL_W / 2;
         ballY = BALL_H / 2;
         repaint();
         setEnabled(false);
         new Timer(TIMER_DELAY, new TimerListener()).start();
      }
   }

   private class TimerListener implements ActionListener {
      @Override
      public void actionPerformed(ActionEvent e) {
         if (ballX + BALL_W / 2 >= getWidth()) {
            stopBall(e);
         } else if (ballY + BALL_H / 2 >= getHeight()) {
            stopBall(e);
         } else {
            ballX++;
            ballY++;
         }
         repaint();
      }

      private void stopBall(ActionEvent e) {
         buttonAction.setEnabled(true);
         ((Timer) e.getSource()).stop();
      }
   }

   private static void createAndShowGui() {
      MoveBall mainPanel = new MoveBall();

      JFrame frame = new JFrame("MoveBall");
      frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}