CODEWITHSUNDEEP
javaswinggraphicsjpanel
charmae
charmae

Reputation: 1080

Draw line over multiple panels in Java

I'm trying to draw a line (Red line in the image) over multiple panels, but I can't seem to make it work. How can I make this possible? Any suggestions?

Drawing of required functionality

Upvotes: 11

Views: 2411

Answers (2)

kleopatra
kleopatra

Reputation: 51535

JDK 7 added JLayer to support visual decorations on top of arbitrary components. For earlier versions, there's the project JXLayer at java.net which actually is its predecessor with very similar api

Here's a rudimentary example, using a custom LayerUI which draws a straight line from one component in a container to another component in a different container. The common parent of the two containers is decorated with a JLayer using that ui:

    JComponent comp = Box.createVerticalBox();
    final JComponent upper = new JPanel();
    final JButton upperChild = new JButton("happy in upper");
    upper.add(upperChild);
    final JComponent lower = new JPanel();
    final JButton lowerChild = new JButton("unhappy in lower");
    lower.add(lowerChild);
    comp.add(upper);
    comp.add(lower);
    LayerUI<JComponent> ui = new LayerUI<JComponent>() {

        @Override
        public void paint(Graphics g, JComponent c) {
            super.paint(g, c);
            Rectangle u = SwingUtilities.convertRectangle(upper, upperChild.getBounds(), c);
            Rectangle l = SwingUtilities.convertRectangle(lower, lowerChild.getBounds(), c);

            g.setColor(Color.RED);
            g.drawLine(u.x, u.y + u.height, l.x, l.y);
        }

    };
    JLayer<JComponent> layer = new JLayer<JComponent>(comp, ui);

Upvotes: 6

Andrew Thompson
Andrew Thompson

Reputation: 168845

Draw onto the glass pane.

Upvotes: 10

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