如何将多个MouseListeners添加到单个JFrame？

Question

我有两件事情要做：在鼠标悬停时突出显示JPanel，在鼠标拖动时移动一个蓝色方块。问题是，这需要我将MouseListeners添加到不同的组件中。当我这样做时，我只能使用一个功能——另一个被阻止了。我该怎么做才能让两个功能都工作？

注意：有时候JFrame不会显示任何东西——你只需要一直运行它，直到它显示为止（通常需要2-3次尝试）。如果它做了任何其他奇怪的事情，就继续运行它，直到它工作。如果之后仍然不起作用，请发表评论

Main（创建JFrame、容器和子对象，并添加鼠标侦听器）

public class Main extends JFrame{
    private static final long serialVersionUID = 7163215339973706671L;
    private static final Dimension containerSize = new Dimension(640, 477);
    static JLayeredPane layeredPane;
    static JPanel container;

    public Main() {
        super("Multiple MouseListeners Test");
        setSize(640, 477);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setResizable(false);
        setVisible(true);

        layeredPane = new JLayeredPane();
        layeredPane.setPreferredSize(containerSize);
        getContentPane().add(layeredPane);

        createContainer();

        layeredPane.add(container, JLayeredPane.DEFAULT_LAYER);

        createChildren(4, 4);

        new MovableObject();

        MovableObjectMouseListener moml = new MovableObjectMouseListener();
        //comment these two out and the highlighter works
        layeredPane.addMouseListener(moml);
        layeredPane.addMouseMotionListener(moml);
    }

    private void createChildren(int columns, int rows){
        for (int i = 0; i < columns; i++){
            for (int j = 0; j < rows; j++){
                JPanel child = new JPanel(new BorderLayout());
                child.setBackground(Color.LIGHT_GRAY);
                //comment this out and you can move the MovableObject
                child.addMouseListener(new HighlightJPanelsMouseListener());
                container.add(child);
            }
        }
    }

    private JPanel createContainer(){
        container = new JPanel();
        container.setLayout(createLayout(4, 4, 1, 1));
        container.setPreferredSize(containerSize);
        container.setBounds(0, 0, containerSize.width, containerSize.height);
        return container;
    }

    private GridLayout createLayout(int rows, int columns, int hGap, int vGap){
        GridLayout layout = new GridLayout(rows, columns);
        layout.setHgap(hGap);
        layout.setVgap(vGap);
        return layout;
    }

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

HighlightJPanelMouseListener（创建将添加到子级的MouseListener）

public class HighlightJPanelsMouseListener implements MouseListener{
    private Border grayBorder = BorderFactory.createLineBorder(Color.DARK_GRAY);

    public HighlightJPanelsMouseListener() {
    }

    public void mouseEntered(MouseEvent e) {
        Component comp = (Component) e.getSource();
        JPanel parent = (JPanel) comp;
        parent.setBorder(grayBorder);
        parent.revalidate();
    }

    public void mouseExited(MouseEvent e) {
        Component comp = (Component) e.getSource();
        JPanel parent = (JPanel) comp;
        parent.setBorder(null);
        parent.revalidate();
    }

    public void mousePressed(MouseEvent e){}
    public void mouseReleased(MouseEvent e){}
    public void mouseClicked(MouseEvent e) {}
}

MovableObject（创建MovableObject）

下载blueSquare。png，或使用其他图像。记住把下面图片的名字改成你的名字。

public class MovableObject {
    public MovableObject() {
        JPanel parent = (JPanel) Main.container.findComponentAt(10, 10);
        ImageIcon icon = null;
        //use any image you might have laying around your workspace - or download the one above
        URL imgURL = MovableObject.class.getResource("/blueSquare.png");

        if (imgURL != null){
            icon = new ImageIcon(imgURL);
        }else{
            System.err.println("Couldn't find file");
        }

        JLabel movableObject = new JLabel(icon);
        parent.add(movableObject);
        parent.revalidate();
    }
}

MovableObjectMouseListener（创建用于MovableObject的MouseListener）

public class MovableObjectMouseListener implements MouseListener, MouseMotionListener{
    private JLabel replacement;
    private int xAdjustment, yAdjustment;

    public void mousePressed(MouseEvent e){
        replacement = null;
        Component c =  Main.container.findComponentAt(e.getX(), e.getY());

        if (!(c instanceof JLabel)){
            return;
        }

        Point parentLocation = c.getParent().getLocation();
        xAdjustment = parentLocation.x - e.getX();
        yAdjustment = parentLocation.y - e.getY();
        replacement = (JLabel)c;
        replacement.setLocation(e.getX() + xAdjustment, e.getY() + yAdjustment);

        Main.layeredPane.add(replacement, JLayeredPane.DRAG_LAYER);
        Main.layeredPane.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
    }

    public void mouseDragged(MouseEvent me){
        if (replacement == null){
            return;
        }

        int x = me.getX() + xAdjustment;
        int xMax = Main.layeredPane.getWidth() - replacement.getWidth();
        x = Math.min(x, xMax);
        x = Math.max(x, 0);

        int y = me.getY() + yAdjustment;
        int yMax = Main.layeredPane.getHeight() - replacement.getHeight();
        y = Math.min(y, yMax);
        y = Math.max(y, 0);

        replacement.setLocation(x, y);
     }


    public void mouseReleased(MouseEvent e){
        Main.layeredPane.setCursor(null);

        if (replacement == null){
            return;
        }

        int xMax = Main.layeredPane.getWidth() - replacement.getWidth();
        int x = Math.min(e.getX(), xMax);
        x = Math.max(x, 0);

        int yMax = Main.layeredPane.getHeight() - replacement.getHeight();
        int y = Math.min(e.getY(), yMax);
        y = Math.max(y, 0);


        Component c = Main.container.findComponentAt(x, y);
        Container parent = (Container) c;
        parent.add(replacement);
        parent.validate();  
    }

    public void mouseClicked(MouseEvent e) {}
    public void mouseMoved(MouseEvent e) {}
    public void mouseEntered(MouseEvent e) {}
    public void mouseExited(MouseEvent e) {}
}

Answer 1

我没有详细查看您的代码，但我建议您需要将拖动MouseListener添加到可移动对象（即JLabel），而不是面板。然后标签将获得拖动事件，面板将获得鼠标输入/退出事件。

这将导致在移动标签时生成mouseExited事件的另一个问题（这是您不希望发生的）。查看：如何避免在任何嵌套组件上启动鼠标，以解决此问题。