JPanel侦听器和线程问题

Question

这是用于以给定的延迟率在帧内的面板上的面板上显示半径变化的圆的代码，但是该代码显示的是最终输出而不是中间阶段，即，圆不是一一出现，而是所有圆立即作为最终输出。 可能存在一些与按钮操作侦听器和面板线程有关的错误。 代码采用初始圆的半径和迭代的总数（要显示的圆的总数），每个下一个圆的半径增加10。

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class ControlCircle extends JFrame {
  private JButton jbtEnlarge = new JButton("Start");
  private JButton jbtShrink = new JButton("Stop");
  private CirclePanel canvas = new CirclePanel();

  private int radius = 0;
  private int iter;

  public ControlCircle() {
    JPanel panel = new JPanel();
    JPanel jp = new JPanel();
    jp.setPreferredSize(new Dimension(300, 0));
    panel.add(jbtEnlarge);
    panel.add(jbtShrink);

    this.add(jp, BorderLayout.WEST);
    this.add(canvas, BorderLayout.CENTER);
    this.add(panel, BorderLayout.SOUTH);

    final JTextField f1 = new JTextField(8),f2 = new JTextField(8);

    jp.setLayout(new FlowLayout(FlowLayout.RIGHT, 50, 30));
    jp.add(new JLabel("Radius"));
    jp.add(f1);
    jp.add(new JLabel("Iteration"));
    jp.add(f2);

    f1.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        radius = Integer.parseInt(new String(f1.getText()));
      }
    });

    f2.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        iter = Integer.parseInt(new String(f2.getText()));
      }
    });

    jbtEnlarge.addActionListener(new EnlargeListener());
    jbtShrink.addActionListener(new ShrinkListener());
  }

  public static void main(String[] args) {
    JFrame frame = new ControlCircle();

    frame.setTitle("ControlCircle");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(800, 600);
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
  }

  class EnlargeListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      canvas.enlarge();
    }
  }

  class ShrinkListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      //canvas.shrink();
    }
  }

  class CirclePanel extends JPanel {
    private int r = radius;

    public void enlarge() {
      //radius += 2;

      repaint();
    }

    public void shrink() {
      radius -= 2;

      repaint();
    }

    protected void paintComponent(Graphics g) {
      super.paintComponent(g);

      for (int i = 0; i < iter; i++) {
        g.drawOval(getWidth() / 2 - r, getHeight() / 2 - r, 2 * r, 2 * r);

        try {
          Thread.sleep(100);
        } catch (Exception exp) {
        }

        r = r + 10;
      }

      r = 0;
    }
  }
}

Answer 1

您遇到的问题很普遍。

Swing是一个单线程框架。 这意味着所有与UI相关的交互都必须在此线程的上下文中发生（又称为事件调度线程）。

除其他事项外，EDT负责调度重涂请求。 如果代码的任何部分停止了该线程（阻止I / O，耗时的过程， Thread.sleep ），则EDT将无法处理任何新事件。

阅读Swing中的并发以了解更多详细信息。

您现在面临两个问题...

1. 您不能阻止EDT
2. 您无法从EDT以外的任何线程更新UI。

幸运的是，有许多解决方案。 最简单的javax.swing.Timer是使用javax.swing.Timer 。

这个计时器触发它在EDT中的滴答事件，但在它自己的线程中等待...

import com.sun.org.apache.bcel.internal.generic.LSTORE;
import java.awt.AlphaComposite;
import java.awt.BorderLayout;
import java.awt.Composite;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Droplets {

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

    public Droplets() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new DropletPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }
    protected static final int MAX_RADIUS = 50;
    protected static final int GROWTH_RATE = 1;

    public class DropletPane extends JPanel {

        private List<Droplet> droplets;

        public DropletPane() {
            droplets = new ArrayList<>(25);
            addMouseListener(new MouseAdapter() {
                @Override
                public void mousePressed(MouseEvent e) {
                    droplets.add(new Droplet(e.getPoint()));
                }
            });

            Timer timer = new Timer(40, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    for (Droplet droplet : droplets.toArray(new Droplet[droplets.size()])) {
                        droplet.grow();
                        if (droplet.getRadius() >= MAX_RADIUS) {
                            droplets.remove(droplet);
                        }
                    }
                    repaint();
                }
            });
            timer.setRepeats(true);
            timer.setCoalesce(true);
            timer.start();
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            Composite comp = g2d.getComposite();
            for (Droplet droplet : droplets) {

                float alpha = 1f - ((float) droplet.getRadius() / (float) MAX_RADIUS);
                g2d.setComposite(AlphaComposite.SrcOver.derive(alpha));
                Point p = droplet.getLocation();
                int radius = droplet.getRadius();
                g2d.drawOval(p.x - (radius / 2), p.y - (radius / 2), radius, radius);
                g2d.setComposite(comp);

            }
            g2d.dispose();
        }
    }

    public class Droplet {

        private Point p;
        private int radius;

        public Droplet(Point p) {
            this.p = p;
        }

        public Point getLocation() {
            return p;
        }

        public int getRadius() {
            return radius;
        }

        public void grow() {
            radius += GROWTH_RATE;
            if (radius > MAX_RADIUS) {
                radius = MAX_RADIUS;
            }
        }
    }
}

扩展示例

当您单击“开始”按钮时，此示例将以随机间隔（在每个墨滴之间）创建随机数量的墨滴。 您可以多次按启动键，它将使输出复合。

import static droplets.Droplets.MAX_RADIUS;
import java.awt.AlphaComposite;
import java.awt.BorderLayout;
import java.awt.Composite;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagLayout;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingWorker;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Droplets02 {

    public static void main(String[] args) {
        new Droplets02();
    }

    public Droplets02() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new DropletPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }
    protected static final int MAX_RADIUS = 50;
    protected static final int GROWTH_RATE = 1;

    public interface Pool {

        public void addDroplet(Droplet droplet);

        public Dimension getSize();
    }

    public class DropletPane extends JPanel implements Pool {

        private List<Droplet> droplets;
        private Timer timer;

        public DropletPane() {

            setLayout(new GridBagLayout());
            JButton button = new JButton("Start");
            button.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    new DropletWorker(DropletPane.this).execute();
                }
            });
            add(button);

            droplets = new ArrayList<>(25);
            timer = new Timer(40, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    if (!droplets.isEmpty()) {
                        for (Droplet droplet : droplets.toArray(new Droplet[droplets.size()])) {
                            droplet.grow();
                            if (droplet.getRadius() >= MAX_RADIUS) {
                                droplets.remove(droplet);
                            }
                        }
                        if (droplets.isEmpty()) {

                            ((Timer) e.getSource()).stop();

                        }
                        repaint();
                    }
                }
            });
            timer.setRepeats(true);
            timer.setCoalesce(true);

        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            Composite comp = g2d.getComposite();
            for (Droplet droplet : droplets) {

                float alpha = 1f - ((float) droplet.getRadius() / (float) MAX_RADIUS);
                g2d.setComposite(AlphaComposite.SrcOver.derive(alpha));
                Point p = droplet.getLocation();
                int radius = droplet.getRadius();
                g2d.drawOval(p.x - (radius / 2), p.y - (radius / 2), radius, radius);
                g2d.setComposite(comp);

            }
            g2d.dispose();
        }

        @Override
        public void addDroplet(Droplet droplet) {
            if (!timer.isRunning()) {
                timer.start();
            }
            droplets.add(droplet);
        }
    }

    public class Droplet {

        private Point p;
        private int radius;

        public Droplet(Point p) {
            this.p = p;
        }

        public Point getLocation() {
            return p;
        }

        public int getRadius() {
            return radius;
        }

        public void grow() {
            radius += GROWTH_RATE;
            if (radius > MAX_RADIUS) {
                radius = MAX_RADIUS;
            }
        }
    }

    public class DropletWorker extends SwingWorker<Void, Droplet> {

        private Pool pool;

        public DropletWorker(Pool pool) {
            this.pool = pool;
        }

        public Pool getPool() {
            return pool;
        }

        protected int random(int minRange, int maxRange) {
            return minRange + (int) (Math.round(Math.random() * (maxRange - minRange)));
        }

        @Override
        protected Void doInBackground() throws Exception {

            int dropCount = random(1, 100);
            Pool pool = getPool();
            Dimension size = pool.getSize();
            for (int index = 0; index < dropCount; index++) {
                Thread.sleep(random(10, 1000));
                int x = random(0, size.width);
                int y = random(0, size.height);
                Droplet droplet = new Droplet(new Point(x, y));
                publish(droplet);
            }

            return null;
        }

        @Override
        protected void process(List<Droplet> chunks) {
            for (Droplet droplet : chunks) {
                getPool().addDroplet(droplet);
            }
        }
    }
}

动画基础

您需要三件事来执行动画。

• 开始状态
• 目标状态
• 增量或时间范围。

（您还需要某种方式来存储当前状态）

起始状态和目标状态不言自明，它们描述了您现在所在的位置以及您要更改的位置。

增量将是在达到“增量”之前每个“时间间隔”（或刻度）上应用于当前状态的数量。

要么

时间范围将是您要用于从开始状态转换到结束状态的时间量。

增量法是一种更简单的机制，但不如时间范围法那么灵活...

设置好这些基本元素之后，您需要以固定的间隔触发某种“滴答”，以便您计算当前状态，该状态可以是从开始状态到目标状态（增量）的线性移动，也可以是随时间（时间范围）变化的进度

最后的全面工作返工

除了尝试在绘画方法中阻止EDT并未能遵循Swing的“ 初始线程”要求外，我发现的唯一另一个重要问题是您对radius和iter值的依赖。

基本上，除非您按Enter键，否则永远不会设置这些……我不是。

本示例使用您发布的代码和第一个示例中的想法...

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class ControlCircles extends JFrame {

    private JButton jbtEnlarge = new JButton("Start");
    private JButton jbtShrink = new JButton("Stop");
    private CirclePanel canvas = new CirclePanel();
    private JTextField f1 = new JTextField(8);
    private JTextField f2 = new JTextField(8);

    public ControlCircles() {
        JPanel panel = new JPanel();
        JPanel jp = new JPanel();
        jp.setPreferredSize(new Dimension(300, 0));
        panel.add(jbtEnlarge);
        panel.add(jbtShrink);

        this.add(jp, BorderLayout.WEST);
        this.add(canvas, BorderLayout.CENTER);
        this.add(panel, BorderLayout.SOUTH);


        jp.setLayout(new FlowLayout(FlowLayout.RIGHT, 50, 30));
        jp.add(new JLabel("Radius"));
        jp.add(f1);
        jp.add(new JLabel("Iteration"));
        jp.add(f2);

        jbtEnlarge.addActionListener(new EnlargeListener());
        jbtShrink.addActionListener(new ShrinkListener());
    }

    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) {
                }

                JFrame frame = new ControlCircles();

                frame.setTitle("ControlCircle");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setSize(800, 600);
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }

        });
    }

    class EnlargeListener implements ActionListener {

        public void actionPerformed(ActionEvent e) {
            int radius = Integer.parseInt(f1.getText());
            int iter = Integer.parseInt(f2.getText());
            canvas.start(radius, iter);

        }

    }

    class ShrinkListener implements ActionListener {

        public void actionPerformed(ActionEvent e) {
            //canvas.shrink();
        }

    }

    class CirclePanel extends JPanel {

        private int radius;
        private int iterations;

        private int iteration;

        private List<Integer> circles;
        private Timer timer;

        public CirclePanel() {
            circles = new ArrayList<>(25);
            timer= new Timer(100, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    iteration++;
                    if (iteration < iterations) {
                        circles.add(radius);
                        radius += 10;
                    } else {
                        ((Timer)e.getSource()).stop();
                    }
                    repaint();
                }
            });
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            int width = getWidth() - 1;
            int height = getHeight()- 1;
            g.drawRect(0, 0, width, height);
            for (Integer radius : circles) {
                int x = (width - radius) / 2;
                int y = (height - radius) / 2;
                g.drawOval(x, y, radius, radius);
            }
        }

        public void start(int radius, int iter) {
            timer.stop();
            circles.clear();
            this.radius = radius;
            iterations = iter;
            iteration = 0;
            System.out.println("radius = " + radius);
            System.out.println("iterations = " + iterations);
            timer.start();
        }
    }
}

该代码通过纠正Swing中的动画常见错误而根据您的问题描述进行工作，但是您的某些代码对我而言并不太有意义（例如， enlarge和shrink ），因此，我着重介绍了您提供的描述。

Answer 2

这个想法是使用“ Start ，“ Stop ”按钮来控制用作画布的面板上的绘图动画，我添加了“ Continue和“ Reset其他控件以更好地解释这个想法。 这些按钮控制动画线程的执行，从而在绘图表面上绘制圆。 我作为内部类分离的绘图表面仅具有绘制所执行内容的功能。 采取此方法的另一种想法是逐步绘制圆，直到完成绘制为止，因此使用了增量绘制。

我使用了上面的代码，并对其进行了一些更改以支持我的想法。 如果您需要更多（通常是更好）的示例，请查看本文 。

下面的代码，我没有完善它以具有生产明智的外观和感觉，但仅用于演示目的。

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;

public class ControlCircle extends JFrame implements Runnable {
  private JButton jbtStart = new JButton("Start");
  private JButton jbtStop = new JButton("Stop");
  private JButton jbtContinue = new JButton("Continue");
  private JButton jbtReset = new JButton("Reset");
  private CirclePanel canvas = new CirclePanel();

  private JTextField f1;
  private int radius = 0;

  private JTextField f2;
  private int iter;

  protected boolean  incrementalPainting;

  /**
   * Flag indicates that a thread is suspended
   */
  private boolean suspended = false;


  /**An instance of the class Thread.*/
  private Thread thread = null;

  public ControlCircle() {
    JPanel panel = new JPanel();
    JPanel jp = new JPanel();
    jp.setPreferredSize(new Dimension(300, 0));
    panel.add(jbtStart);
    panel.add(jbtStop);
    panel.add(jbtContinue);
    panel.add(jbtReset);

    this.add(jp, BorderLayout.WEST);
    this.add(canvas, BorderLayout.CENTER);
    this.add(panel, BorderLayout.SOUTH);

    f1 = new JTextField(8);
    f2 = new JTextField(8);

    jp.setLayout(new FlowLayout(FlowLayout.RIGHT, 50, 30));
    jp.add(new JLabel("Radius"));
    jp.add(f1);
    jp.add(new JLabel("Iteration"));
    jp.add(f2);


    jbtStart.addActionListener(new StartListener());
    jbtStop.addActionListener(new StopListener());
    jbtContinue.addActionListener(new ContinueListener());
    jbtReset.addActionListener(new ResetListener());
  }

  public static void main(String[] args) {
    JFrame frame = new ControlCircle();

    frame.setTitle("ControlCircle");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(800, 600);
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
  }

  class StartListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      if (thread == null) {
        repaint();
        startThread();
      }
    }
  }

  class StopListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      if (thread != null){
        mySuspend();
      }
    }
  }

  class ContinueListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      myResume();
    }
  }

  class ResetListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      if (thread != null) {
        stopThread();
      }
      repaint();
    }

  }

  /**
   * my Suspend
   */
  private void mySuspend() {
    System.out.println("mySyspend()");
    suspended = true;
  }

  /**
   * my Resume
   */
  private synchronized void myResume(){
    System.out.println("myResume()");
    suspended = false;
    notifyAll();
  }

  public void run(){
    System.out.println("run() - started");

    Thread me = Thread.currentThread();
    while (thread == me) {
      radius = Integer.parseInt(f1.getText());
      iter = Integer.parseInt(f2.getText());
      for (int i = 0; i < iter; i++) {
        if (thread == null) return;
        incrementalPainting = true;
        myRepaint();
        try {
          Thread.sleep(1000);
        }
        catch(InterruptedException e){}
        radius += 10;
      }
      if(thread != null) thread = null; // exiting while
    }
    System.out.println("run() - exiting");
  }

  /**
   * start Thread
   */
  private void startThread(){
    System.out.println("startThread()");
    if(thread == null){
      thread = new Thread(this);
      thread.start();
    }
  }

  /**
   *  stop Thread
   */
  private synchronized void stopThread() {
    System.out.println("stopThread()");
    thread = null; // exiting from while
    if (suspended) {
      suspended = false;
      notify();
    }
  }

  /**
   * This is called from the run method to invoke painting.
   */
  private void myRepaint() {
    System.out.println("myRepaint()");
    incrementalPainting = true;
    repaint();
    synchronized (this) {
      while (incrementalPainting) {
        System.out.println("wait while incremental painting");
        try {
          wait();
        } catch (InterruptedException e) {
          System.out.println("interrupted");
        }
      }
    }

    suspend();
  }
  /**
   * This method should place somewhere when run() has started. Perfectly
   * when repaint() performed.
   */
  private void suspend(){
    System.out.println("suspend()");
    synchronized (this) {
      while (suspended) {
        System.out.println("wait while suspended");
        try {
          wait();
        } catch (InterruptedException e) {
          System.out.println("interrupted");
        }
      }
    }

  }

  public synchronized void myPaint(Graphics g) {
    if (g == null){
      if (incrementalPainting){
        incrementalPainting = false;
        notifyAll();
      }
      return;
    }
    if (incrementalPainting){
      myDraw(g);
      incrementalPainting = false;
      notifyAll();

    }
    else {
      myDraw(g);
    }
  }

  public void myDraw(Graphics g){
    g.drawOval(getWidth() / 2 - radius, getHeight() / 2 - radius, 2 * radius, 2 * radius);
  }

  protected final class CirclePanel extends JPanel {
    //Offscreen buffer of this canvas
    private BufferedImage backBuffer = null;

    public void paintComponent (Graphics g) {
      System.out.println("incrementalPainting="+incrementalPainting);
      // First paint background
      super.paintComponent(g);
      Dimension d = this.getSize();
      if (! incrementalPainting)
        backBuffer = (BufferedImage) this.createImage(d.width, d.height);
      Graphics2D g2 = backBuffer.createGraphics();
      if (! incrementalPainting){
        g2.setColor(Color.WHITE);
        g2.fillRect(0,0, d.width, d.height);
      }
      myPaint(g2);
      g.drawImage(backBuffer, 0, 0, this);

    }

  }

}