How to “do something” on Swing component resizing?

Question

I\'ve a class which extends JPanel. I overwrote protected void paintComponent(Graphics g).

There is a variable which has to be recalculate

Answer 1

Like Adam Paynter suggested, you can also add an inner class to your code, like this:

class ResizeListener extends ComponentAdapter {
        public void componentResized(ComponentEvent e) {
            // Recalculate the variable you mentioned
        }
}

The code you have entered between the innermost brackets will be executed everytime the component get resized.

Then you add this listener to your component with

myJPanel.addComponentListener(new ResizeListener());

You can get your component by using e.getComponent(). This way you can call any method of your component from inside the inner class like

e.getComponent().getWeight();