Does MousePressed Method Inhibit MouseReleased from Triggering in JLabel Drag and Drop?-javaTutorial-php.cn

Does MousePressed Method Inhibit MouseReleased from Triggering in JLabel Drag and Drop?

Mary-Kate Olsen

Release： 2024-10-24 02:41:29

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Does MousePressed Method Inhibit MouseReleased from Triggering in JLabel Drag and Drop?

JLabel Mouse Events for Drag and Drop

Question:

Implementing drag and drop for a JLabel via mouse event overrides, the mouseReleased event fails to trigger upon mouse release when defined within the mousePressed event. Is there something am I doing incorrectly?"

Code:

<code class="java">Thumbnails[I_Loop].addMouseListener( new MouseAdapter() {
    public void  mouseReleased(MouseEvent me) {
           System.out.println("here mouse released");
      }
    public void mousePressed(MouseEvent me) {
        System.out.println("here mouse pressed");
        JComponent comp = (JComponent) me.getSource();
        TransferHandler handler = comp.getTransferHandler();
        handler.exportAsDrag(comp, me, TransferHandler.COPY);
    });</code>

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Answer:

While @Thomas's solution is correct, here are two alternative approaches to consider:

1. Using JLayeredPane:

This example demonstrates dragging a component using JLayeredPane. This variation expands on the same concept, while a more recent example uses a similar approach.

Code:

<code class="java">// ...
private Point mousePt;
private Point dragPt;
private Rectangle bounds;

public MouseDragTest() {
    this.addMouseMotionListener(new MouseMotionAdapter() {

        @Override
        public void mouseDragged(MouseEvent e) {
            int dx = e.getX() - mousePt.x;
            int dy = e.getY() - mousePt.y;
            dragPt.setLocation(dragPt.x + dx, dragPt.y + dy);
            super.mouseDragged(e);
        }
    });
    this.addMouseListener(new MouseAdapter() {

        @Override
        public void mousePressed(MouseEvent e) {
            bounds = getBounds();
            Point p = SwingUtilities.convertPoint(this, e.getPoint(), Bounds.Parent);
            if (bounds.contains(p)) {
                dragPt = p;
                mousePt = e.getPoint();
            }
        }
    });
    // ...
}</code>

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2. Using MouseMotionListener:

This code demonstrates using a MouseMotionListener. This more complex example uses the same principle.

Code:

<code class="java">// ...
private Point offset;

public MouseDragTest() {
    this.addMouseMotionListener(new MouseMotionAdapter() {

        @Override
        public void mouseDragged(MouseEvent e) {
            Point delta = e.getPoint();
            Point pt = new Point(getLocation().x + delta.x - offset.x,
                    getLocation().y + delta.y - offset.y);
            setLocation(pt);
        }
    });
    this.addMouseListener(new MouseAdapter() {

        @Override
        public void mousePressed(MouseEvent e) {
            offset = e.getPoint();
        }
    });
    // ...
}</code>

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