Question

When a user clicks on the corner of a JFrame to resize and drags the mouse around, the JFrame redraws based on the current position of the mouse as the user drags. How can you listen to these events?

Below is the what I have currently tried:

public final class TestFrame extends JFrame {
    public TestFrame() {
        this.addComponentListener(new ComponentAdapter() {
            public void componentResized(ComponentEvent e) {
                // This is only called when the user releases the mouse button.
                System.out.println("componentResized");
            }
        });
    }

    // These methods do not appear to be called at all when a JFrame
    // is being resized.
    @Override
    public void setSize(int width, int height) {
        System.out.println("setSize");
    }

    @Override
    public void setBounds(Rectangle r) {
        System.out.println("setBounds A");
    }

    @Override
    public void setBounds(int x, int y, int width, int height) {
        System.out.println("setBounds B");
    }
}

How can I determine and constrain how the user resizes a window (based on the current aspect ratio of the window) as they are dragging around the mouse around?

Answer 1

You probably need to override something like validate (don’t forget to call the super). Of course, that still may not work if you are using a windowing system to configured to drag outlines.