CODEWITHSUNDEEP
javaswingnetbeanslinedraw
AgentPaper
AgentPaper

Reputation: 109

Drawing on a jPanel that has sub-panels

I have a jPanel, which contains a number of sub-panels that can be dragged around. What I want to do, is to draw lines connecting some of those sub-panels together.

However, while it seems like this should be simple, it's proven very frustrating. The best I've gotten, is to override the paintComponent function in the original jPanel as such:

panCharDisplay = new javax.swing.JPanel() {
    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        paintLines(g);
    }
};

And then draw the lines as such:

public void paintLines(Graphics g) {
    g.setColor(Color.BLUE);
    for (Character c : characters) {
        if (c.female && c.spouse != null) {
            g.drawLine(c.display.getX(), c.display.getY(), c.spouse.display.getX(), c.spouse.display.getY());
        }
    }
}

This works in a sense, in that it does technically draw the lines, in the right place, the right color, and so on, but only if I scroll away from where the line should be, and then scroll back. Whenever I drag a component around it causes weird graphics errors, as it draws only parts of the line and doesn't erase the ones before. The lines also show up below the sub-panels instead of over them, making them hidden a lot of the time.

I assume the reason for this is that I'm drawing the lines at the wrong time, and need to draw them after drawing the sub-panels, and also make sure that they are re-drawn every time the panels are dragged around.

Is there another place I can put in an override to make the lines show up more consistently? Another method I tried, was to make a class that extends JPanel, and try to use that to handle the drawing, but I couldn't get it to work at all.

Upvotes: 0

Views: 582

Answers (2)

camickr
camickr

Reputation: 324118

Whenever I drag a component around it causes weird graphics errors, as it draws only parts of the line and doesn't erase the ones before.

You probably need to invoke repaint() on the panel's parent as you drag the panel around.

The lines also show up below the sub-panels instead of over them, making them hidden a lot of the time.

You should be able to override either the paint() or paintChildren() method instead of the paintComponent() method. Whichever method you override make sure to invoke super.XXX() first so that the default painting is done before you attempt to draw your lines.

Personally I like the lines painted below the component as is demonstrated in trashgod's GraphPanel example. The example does custom painting for the shapes, but I would guess the logic would be similar for the components.

Upvotes: 2

StanislavL
StanislavL

Reputation: 57381

You can get this JConnector project and use as is or adapt the sources as you need.

Upvotes: 1

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