Java( Swing ): MouseMoved not working at all

Question

这让我抓狂。这一定是一个非常简单的问题，但我不可能看到它。

基本上永远不会调用 mouseMoved。下面是代码。

public class MouseMotionThing {
public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {

        @Override
        public void run() {
            JFrame jFrame = new JFrame();
            jFrame.setContentPane(new ContentPane());
            jFrame.setSize(400, 400);
            jFrame.setVisible(true);
            jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        }
    }); 
}
}

还有我的面板。此实现使用 MouseInputListener:

class ContentPane extends JPanel implements MouseInputListener {
int x = 0, y = 0;

public ContentPane() {
    setOpaque(true);
    addMouseListener(this);
    addMouseMotionListener(this);

}

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

    g.drawLine(0, 0, x, y);
}

@Override
public void mouseDragged(MouseEvent e) {
    System.out.println("Mouse Dragged!");
}

@Override
public void mouseMoved(MouseEvent e) {
    System.out.println("CALLED MOUSE MOVED");
    x = e.getX();
    y = e.getY();

    repaint();
}

@Override
public void mouseClicked(MouseEvent e) {
}

@Override
public void mousePressed(MouseEvent e) {
}

@Override
public void mouseReleased(MouseEvent e) {
}

@Override
public void mouseEntered(MouseEvent e) {
}

@Override
public void mouseExited(MouseEvent e) {
}
}

而此替代实现仅使用 MouseMotionListener:

class ContentPane extends JPanel implements MouseMotionListener {
int x = 0, y = 0;

public ContentPane() {
    setOpaque(true);
    addMouseMotionListener(this);

}

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

    g.drawLine(0, 0, x, y);
}

@Override
public void mouseDragged(MouseEvent e) {
    System.out.println("Mouse Dragged!");
}

@Override
public void mouseMoved(MouseEvent e) {
    System.out.println("CALLED MOUSE MOVED");
    x = e.getX();
    y = e.getY();

    repaint();
}
}

在上述替代实现中，都没有调用过 mouseMoved。我每次都在添加正确的听众，但它根本不起作用。 mouseDragged 虽然工作正常。我错过了什么？

LE:我在 Ubuntu 12.10 和 JDK 7 上测试了代码，运行良好。然后当我回到我的 W8 机器时，它开始工作了。除了重新启动笔记本电脑外，我什么也没做。我无法重现问题，也无法追踪到它，但如果我再次遇到它并设法找到一些东西，我会回来的。

Answer 1

尚不清楚哪里出了问题；它可能有助于进行完整构建。作为引用，我重构了你的 sscce使用 MouseAdapter 并从 JPanel 中删除泄漏的 this。

import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class MouseMotionThing {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame jFrame = new JFrame();
                jFrame.add(new MousePanel());
                jFrame.pack();
                jFrame.setSize(400, 400);
                jFrame.setVisible(true);
                jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            }
        });
    }

    private static class MousePanel extends JPanel {

        Point p = new Point();

        public MousePanel() {
            setOpaque(true);
            addMouseMotionListener(new MouseHandler());
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.drawLine(0, 0, p.x, p.y);
        }

        private class MouseHandler extends MouseAdapter {

            @Override
            public void mouseDragged(MouseEvent e) {
                update(e);
            }

            @Override
            public void mouseMoved(MouseEvent e) {
                update(e);
            }

            private void update(MouseEvent e) {
                System.out.println(e.paramString());
                MousePanel.this.p = e.getPoint();
                MousePanel.this.repaint();
            }
        }
    }
}