Java:如何控制 JPanel 纵横比?

I have a JPanel which I want to remain a square however I want it to size so that it fills the maximum amount of space possible in its parent JFrame but remains square i.e. it takes the shortest side of the JFrame as the square width.

I've searched the net, checked all layout managers and none seem to have a simple solution to this very simple problem.

解决方案

You may use a GridBagLayout and ComponentListener,

For example: (inspired from: https://community.oracle.com/thread/1265752?start=0&tstart=0)

public class AspectRatio {
    public static void main(String[] args) {
        final JPanel innerPanel = new JPanel();
        innerPanel.setBackground(Color.YELLOW);

        final JPanel container = new JPanel(new GridBagLayout());
        container.add(innerPanel);
        container.addComponentListener(new ComponentAdapter() {
            @Override
            public void componentResized(ComponentEvent e) {
                resizePreview(innerPanel, container);
            }
        });
        final JFrame frame = new JFrame("AspectRatio");
        frame.getContentPane().add(container);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(600, 600);
        frame.setVisible(true);
    }

    private static void resizePreview(JPanel innerPanel, JPanel container) {
        int w = container.getWidth();
        int h = container.getHeight();
        int size =  Math.min(w, h);
        innerPanel.setPreferredSize(new Dimension(size, size));
        container.revalidate();
    }
}