Java Swing: How JToolbar changes appearance of a button?

Question

When you add a JButton to a JToolbar, the button takes a specific look (not the same that if you add it to a Jpanel). I created some component similar to a JToolbar and I would like the same behavior. Problem: I checked the JToolbar class to find some specific code in charge to change the appearence of added components (change component specific paint method or UI delegates, etc). I didn't find anything! I don't understand how JToolbar works. Could anyone explain me how it works?

Thanks a lot,

Herve Guillaume

Answer 1

This appears to be handled by the update() method of the MetalButtonUI class. Here is the code from JDK5_07:

public void update(Graphics g, JComponent c) {
    AbstractButton button = (AbstractButton)c;
    if ((c.getBackground() instanceof UIResource) &&
              button.isContentAreaFilled() && c.isEnabled()) {
        ButtonModel model = button.getModel();
        if (!MetalUtils.isToolBarButton(c)) {
            if (!model.isArmed() && !model.isPressed() &&
                    MetalUtils.drawGradient(
                    c, g, "Button.gradient", 0, 0, c.getWidth(),
                    c.getHeight(), true)) {
                paint(g, c);
                return;
            }
        }
        else if (model.isRollover() && MetalUtils.drawGradient(
                    c, g, "Button.gradient", 0, 0, c.getWidth(),
                    c.getHeight(), true)) {
            paint(g, c);
            return;
        }
    }
    super.update(g, c);
}

The isToolBarButton() method just checks if the parent Container is a JToolBar, so I guess one solution is to always add your JButton to a JToolBar and then add the toolbar to your real Container.

Otherwise, I guess, you would need to write your own custom UI and override the update() method.