Drawing graphics on top of a JButton

Question

I have a situation wherein I have a bunch of JButtons on a GridLayout. I need each of the JButtons to have:

1. a background image (but retain the ability to keep the default button look if needed)
2. custom graphics drawn on top by other classes

I have no trouble with the background image, since I am using setIcon() but I am having problems drawing things on top of the background. At one point I was able to draw on top of the button, but after the button was clicked, the drawings disappeared. How can make the button keep this drawing state?

Basically, I need a way for my JButtons to have public methods that would allow another class to draw anything on it such as:

public void drawSomething() {
  Graphics g = this.getGraphics();
  g.drawOval(3,2,2,2);
  repaint();
}

or

public Graphics getGraphics() {
  return this.getGraphics();
}

then another class could do this:

button.getGraphics().drawSomething();

The latter is more what I am looking for but the first is equally useful.

Is there any way to go about this? Also, overriding the parent class method paintComponent() doesn't help since I need each button to have different graphics.

Answer 1

you can subclass JButton and override paintComponent(). you can handle each button having a different graphic by providing an external 'painter' to the subclass. Or just have a different subclass for each different graphic.

public class MyButton extends JButton {
    private Painter painter;

    public void paintComponent(Graphics g) {
       super.paintComponent(Graphics g);
       painter.paint(g);
    }
}

public interface Painter {
    public void paint(Graphics g);
}

you cannot just paint on the button as you are doing as the painting will get lost when the button is next repainted.

Answer 2

You can create a BufferedImage and do custom painting on it and then draw the image in your custom paintComponent(...) method.

Look at the DrawOnImage example from Custom Painting Approaches.