特定的RepaintManager可以用于特定的JPanel吗？

Question

我了解到，RepaintManager将合并调用来重新绘制()，对于99%的呈现来说，这是很好的。我有一个JPanel，我想更新一个定时器(100毫秒)的图像，以提供平滑的渲染像视频。在实践中，除非鼠标被移动，否则RepaintManager似乎会窃取/忽略其他每一个重绘()。我想知道我有什么选择来解决这个问题。我还查看了paintImmediately()，但是它产生了与repaint()相同的行为，因此不太有用。提前感谢您提出的有益想法！

1. 是否可以为特定的RepaintManager创建和使用自定义JPanel，并对其他一切使用默认值？
2. 是否有一种方法可以让默认的RepaintManger确定某个面板是“脏的”，从而使它被重新绘制而不是被忽略？

下面是一些说明实现的代码，您将注意到(至少在我的Linux测试中)，数字将跳过几乎所有其他序列。

    public class PanelRepaintIssue
    {
        private static final int kWIDTH = 200;
        private static final int kHEIGHT = 100;
        private static final int kNUM_IMAGES = 10;
        private static final int kREPAINT_DELAY = 250;

        private final JPanel _ImagePanel;
        private final BufferedImage[] _Images;
        private final Timer _Timer;

        private TimerTask _TimerTask;
        private int _Index;

        public PanelRepaintIssue()
        {
            _Index = 0;

            _ImagePanel = new JPanel()
            {
                @Override
                protected void paintComponent(Graphics g)
                {
                    super.paintComponent(g);

                    if (_Index < kNUM_IMAGES)
                    {
                        g.drawImage(_Images[_Index], 0, 0, null);
                    }
                }
            };
            _ImagePanel.setSize(new Dimension(kWIDTH, kHEIGHT));
            _ImagePanel.setPreferredSize(new Dimension(kWIDTH, kHEIGHT));

            _Images = new BufferedImage[kNUM_IMAGES];

            for (int i = 0; i < _Images.length; ++i)
            {
                _Images[i] = new BufferedImage(kWIDTH, kHEIGHT, BufferedImage.TYPE_INT_ARGB);
                Graphics2D t2d = _Images[i].createGraphics();
                t2d.setColor(Color.BLACK);
                t2d.fillRect(0, 0, kWIDTH, kHEIGHT);
                t2d.setColor(Color.RED);
                t2d.drawString(Integer.toString(i), kWIDTH/2, kHEIGHT/2);
                t2d.dispose();
            }

            _Timer = new Timer(this.getClass().getName());
        }

        public JPanel getPanel()
        {
            return _ImagePanel;
        }

        public void start()
        {
            if (null != _TimerTask)
            {
                _TimerTask.cancel();
                _TimerTask = null;
            }

            _TimerTask = new TimerTask()
            {
                @Override
                public void run()
                {
                    ++_Index;

                    if (_Index >= kNUM_IMAGES)
                    {
                        _Index = 0;
                    }

                    _ImagePanel.repaint();
                    // Also tried _ImagePanel.paintImmediately(0, 0, kWIDTH, kHEIGHT);
                }
            };

            _Timer.scheduleAtFixedRate(_TimerTask, 1000, kREPAINT_DELAY);
        }

        public static void main(String[] args)
        {
            PanelRepaintIssue tPanel = new PanelRepaintIssue();
            tPanel.start();
            JFrame tFrame = new JFrame("PanelRepaintIssue");
            tFrame.add(tPanel.getPanel());
            tFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            tFrame.setResizable(false);
            tFrame.pack();
            tFrame.setVisible(true);
        }
    }

Answer 1

这个问题最终是特定于Linux的平台，可能是其他的，但只有Linux进行了测试。通过使用以下方法纠正或避免了这一问题：

_ImagePanel.repaint();
Toolkit.getDefaultToolkit().sync();

添加Toolkit.getDefaultToolkit().sync()确保了重新绘制()实际上更新了屏幕上的图像。

Answer 2

我还是不知道画的问题是什么。

我对你的代码做了一些修改。

1. 我使用SwingUtilities invokeLater方法将Swing组件的创建和执行放在事件调度线程 (EDT)上。
2. 除了绘画代码之外，我从paintComponent方法中删除了所有内容。在paintComponent方法中，除了绘制什么都不应该发生。

这是我运行的代码。

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Timer;
import java.util.TimerTask;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class PanelRepaintIssue {
    private static final int kWIDTH = 200;
    private static final int kHEIGHT = 100;
    private static final int kNUM_IMAGES = 10;
    private static final int kREPAINT_DELAY = 250;

    private final JPanel _ImagePanel;
    private final BufferedImage[] _Images;
    private final Timer _Timer;

    private TimerTask _TimerTask;
    private int _Index;
    private int _TimerCnt;
    private int _PaintCnt;

    public PanelRepaintIssue() {
        _Index = 0;
        _TimerCnt = 0;
        _PaintCnt = 0;

        _ImagePanel = new JPanel() {

            private static final long serialVersionUID = 1L;

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

//              if (_Index < kNUM_IMAGES) {
                    g.drawImage(_Images[_Index], 0, 0, null);
                    ++_PaintCnt;
//                  System.out.println("Timer: " + _TimerCnt + 
//                          " Paint: " + _PaintCnt);
//              }
            }
        };
        _ImagePanel.setSize(new Dimension(kWIDTH, kHEIGHT));
        _ImagePanel.setPreferredSize(
                new Dimension(kWIDTH, kHEIGHT));

        _Images = new BufferedImage[kNUM_IMAGES];

        for (int i = 0; i < _Images.length; ++i) {
            _Images[i] = new BufferedImage(kWIDTH, kHEIGHT, 
                    BufferedImage.TYPE_INT_ARGB);
            Color color = new Color(128, 128, 20 * i);
            Graphics g = _Images[i].getGraphics();
            g.setColor(color);
            g.fillRect(0, 0, kWIDTH, kHEIGHT);
            g.dispose();
        }

        _Timer = new Timer(this.getClass().getName());
    }

    public JPanel getPanel() {
        return _ImagePanel;
    }

    public void start() {
        if (null != _TimerTask) {
            _TimerTask.cancel();
            _TimerTask = null;
        }

        _TimerTask = new TimerTask() {
            @Override
            public void run() {
                ++_TimerCnt;
                ++_Index;

                if (_Index >= kNUM_IMAGES) {
                    _Index = 0;
                }

                _ImagePanel.repaint();

                System.out.println("Timer: " + _TimerCnt + 
                        " Paint: " + _PaintCnt);
                // Also tried _ImagePanel.paintImmediately
                //    (0, 0, kWIDTH, kHEIGHT);
            }
        };

        _Timer.scheduleAtFixedRate(_TimerTask, 1000, 
                kREPAINT_DELAY);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                PanelRepaintIssue tPanel = 
                        new PanelRepaintIssue();
                tPanel.start();
                JFrame tFrame = new JFrame("PanelRepaintIssue");
                tFrame.add(tPanel.getPanel());
                tFrame.setDefaultCloseOperation(
                        JFrame.EXIT_ON_CLOSE);
                tFrame.setResizable(false);
                tFrame.pack();
                tFrame.setVisible(true);
            }   
        });
    }
}

编辑:根据评论中提供的新信息，而不是原来的问题，我重新编写了代码。

我没发现有什么问题。下面是来自println方法的最后4行Timer。

Timer: 200 Paint: 201
Timer: 201 Paint: 202
Timer: 202 Paint: 203
Timer: 203 Paint: 205

正如您所看到的，除了最后一行之外，数字是同步的。这种差异可能是因为我通过Eclipse取消了这个程序。

这是修改后的代码。我还是不明白这个问题。

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Timer;
import java.util.TimerTask;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class PanelRepaintIssue {
    private static final int kWIDTH = 300;
    private static final int kHEIGHT = 200;
    private static final int kNUM_IMAGES = 10;
    private static final int kREPAINT_DELAY = 250;

    private final JPanel _ImagePanel;
    private final BufferedImage[] _Images;
    private final Timer _Timer;

    private TimerTask _TimerTask;
    private int _Index;
    private int _TimerCnt;
    private int _PaintCnt;

    public PanelRepaintIssue() {
        _Index = 0;
        _TimerCnt = 0;
        _PaintCnt = 0;

        _ImagePanel = new JPanel() {

            private static final long serialVersionUID = 1L;

            @Override
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);
                g.drawImage(_Images[_Index], 0, 0, null);
                ++_PaintCnt;
            }
        };
        _ImagePanel.setSize(new Dimension(kWIDTH, kHEIGHT));
        _ImagePanel.setPreferredSize(
                new Dimension(kWIDTH, kHEIGHT));

        _Images = new BufferedImage[kNUM_IMAGES];

        int x = kWIDTH / 2;
        int y = kHEIGHT / 2;

        for (int i = 0; i < _Images.length; ++i) {
            _Images[i] = new BufferedImage(kWIDTH, kHEIGHT, 
                    BufferedImage.TYPE_INT_ARGB);
            String text = Integer.toString(i + 1);
            Graphics g = _Images[i].getGraphics();
            g.setFont(g.getFont().deriveFont(80f));
            g.setColor(Color.BLACK);
            g.drawString(text, x, y);
            g.dispose();
        }

        _Timer = new Timer(this.getClass().getName());
    }

    public JPanel getPanel() {
        return _ImagePanel;
    }

    public void start() {
        if (null != _TimerTask) {
            _TimerTask.cancel();
            _TimerTask = null;
        }

        _TimerTask = new TimerTask() {
            @Override
            public void run() {
                ++_TimerCnt;
                ++_Index;

                if (_Index >= kNUM_IMAGES) {
                    _Index = 0;
                }

                updateImagePanel();

                System.out.println("Timer: " + _TimerCnt + 
                        " Paint: " + _PaintCnt);
            }
        };

        _Timer.scheduleAtFixedRate(_TimerTask, 1000, 
                kREPAINT_DELAY);
    }

    private void updateImagePanel() {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                _ImagePanel.repaint();
            }
        });
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                PanelRepaintIssue tPanel = 
                        new PanelRepaintIssue();
                tPanel.start();
                JFrame tFrame = new JFrame("PanelRepaintIssue");
                tFrame.add(tPanel.getPanel());
                tFrame.setDefaultCloseOperation(
                        JFrame.EXIT_ON_CLOSE);
                tFrame.setResizable(false);
                tFrame.pack();
                tFrame.setVisible(true);
            }   
        });
    }
}

再次编辑:我在准备午餐的时候运行了你的代码。下面是println输出的最后几行。

Timer: 4037 Paint: 4038
Timer: 4038 Paint: 4040
Timer: 4039 Paint: 4040
Timer: 4040 Paint: 4041
Timer: 4041 Paint: 4042
Timer: 4042 Paint: 4043

正如你所看到的，动画中没有一个帧被丢弃。以每帧250毫秒的速度，Swing重绘管理器在绘制图像时没有问题。

为了好玩，我将kREPAINT_DELAY降低到每帧10毫秒。是100帧每秒。

下面是测试中的println行。

Timer: 1104 Paint: 1105
Timer: 1105 Paint: 1106
Timer: 1106 Paint: 1107
Timer: 1107 Paint: 1108
Timer: 1108 Paint: 1109
Timer: 1109 Paint: 1110

再一次，没有一个框掉下来。

问题可能在代码中，而不是在Swing重绘管理器中。