我有单独的类来处理鼠标侦听器。但是当我在另一个类中使用它时，它不起作用，并且我还不知道如何解决这个问题。这是我的Handler类：

some import stuff

public class Handler implements MouseListener, MouseMotionListener {
private final Canvas canvas;

public Handler(Canvas targetCanvas) {
    this.canvas = targetCanvas;
}

// recasting exception
public Canvas getTargetCanvas() {
    return canvas;
}
...
...
@Override
public void mouseDragged(MouseEvent e) {
    // recasting exception
    DrawingCanvas dC = (DrawingCanvas) getTargetCanvas();
    dC.setMouseDragged(true);
}

@Override
public void mouseMoved(MouseEvent e) {
    // recasting exception
    DrawingCanvas dCanvas = (DrawingCanvas) getTargetCanvas();
    dCanvas.setMouseClicked(true);
    dCanvas.setMouseCoordinates(e.getPoint());
}
}

DrawingCanvas类：

some import stuff

public class DrawingCanvas extends Canvas {
private boolean isMouseDragged, isMouseMoved;
private Point mouseCoordinates;

public DrawingCanvas() {
    this.setPreferredSize(new Dimension(790, 500));
    this.setBackground(Color.WHITE);
}

public Point getMouseCoordinates() {
    return mouseCoordinates;
}

public boolean isIsMouseDragged() {
    return isMouseDragged;
}

public boolean isIsMouseMoved() {
    return isMouseMoved;
}
...
...
public void setMouseDragged(boolean dragged) {
    isMouseDragged = dragged;
}

public void setMouseMoved(boolean moved) {
    isMouseMoved = moved;
}

public void setMouseCoordinates(Point coordinates) {
    mouseCoordinates = coordinates;
}
}

StatusBar类：

some import stuff

public class StatusBar extends JPanel {
private JLabel statusBar;

public StatusBar() {
    statusBar = new JLabel();

    this.setPreferredSize(new Dimension(500, 30));
    this.setBackground(new Color(242,241,240));
    this.add(statusBar, new BorderLayout(5,0));

}

public JLabel getStatusBar() {
    return statusBar;
}

public void setStatusBar(JLabel statusBar) {
    this.statusBar = statusBar;
}
}

和MouseEventGUI类：

some import stuff

public class MouseEventGUI extends JFrame {
private DrawingCanvas drawingCanvas;
private StatusBar statusBar;
private MenuBar menuBar;

public MouseEventGUI() {
    super("Learn Mouse Event");

    drawingCanvas = new DrawingCanvas();
    statusBar = new StatusBar();
    menuBar = new MenuBar();

    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setPreferredSize(new Dimension(750, 560));

    this.add(menuBar, BorderLayout.NORTH);
    this.add(drawingCanvas, BorderLayout.CENTER);       
    this.add(statusBar, BorderLayout.SOUTH);
    this.addMouseListener(new Handler(drawingCanvas));
    this.addMouseMotionListener(new Handler(drawingCanvas));

    if(drawingCanvas.isIsMouseMoved()){
        statusBar.getStatusBar().setText(String.format("%d, %d", 
                drawingCanvas.getMouseCoordinates().x, 
                drawingCanvas.getMouseCoordinates().y));
    } else {
        statusBar.getStatusBar().setText("Mouse is not listened.");
    }    
}
}

当我运行该程序时，在状态栏中显示“未监听鼠标”（请参见MouseEventGUI类），希望它在画布中移动时显示鼠标光标的坐标。

[更新]

如果在同一个类中，则 可以 进行一些修改 很好地工作 。这是DrawingCanvas类的代码：

public class DrawingCanvas extends JPanel {
private boolean isMouseClicked,
        isMouseMoved;
private Point mouseCoordinates;
protected StatusBar statusBar;
protected MenuBar menuBar;


public DrawingCanvas(StatusBar st) {
    setPreferredSize(new Dimension(790, 500));
    setBackground(Color.WHITE);
    statusBar = st;
    Handlers handlers = new Handlers();
    addMouseListener(handlers);
    addMouseMotionListener(handlers);
}

**// inner class**
protected class Handlers extends MouseAdapter implements MouseListener, MouseMotionListener {

    @Override
    public void mouseClicked(MouseEvent e) {
        statusBar.getStatusBar().setText("Mouse clicked.");
    }

    @Override
    public void mouseMoved(MouseEvent e) {            
        statusBar.getStatusBar().setText(String.format("%d, %d", e.getX(),e.getY()));

    }

}
}

这里是MouseEventGUI类：

public class MouseEventGUI extends JFrame {
private DrawingCanvas drawingCanvas;
private StatusBar statusBar;
private MenuBar menuBar;

public MouseEventGUI() {
    super("Learn Mouse Event");

    statusBar = new StatusBar();
    menuBar = new MenuBar();
    drawingCanvas = new DrawingCanvas(statusBar);

    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setPreferredSize(new Dimension(750, 560));
    this.add(menuBar, BorderLayout.NORTH);
    this.add(drawingCanvas, BorderLayout.CENTER);       
    this.add(statusBar, BorderLayout.SOUTH);
}
}

但是，出于 可重用的 原因，我计划将其放在单独的类中。