JFrame maintains same window aspect ratio when resized

php editor Zimo brings you this issue of java Q&A. We will discuss how to maintain the same window aspect ratio when resizing a JFrame. JFrame is a commonly used window component in Java, but maintaining the aspect ratio when resizing has always been a concern for developers. In this article, we will share some practical methods and tips to help you solve this dilemma. Let’s dive in!

Question content

I am studying linux gnome.

I want the window to maintain a 16:9 ratio. For example, if you scale the width, the code only modifies the height, so user input is not touched.

With this approach, the window resizes itself beyond what it should be. For example, I scaled the width slightly, but the height is much larger than it should be.

import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Main
{
    public static void main(String[] args)
    {
        JPanel panel = new JPanel();
        panel.setPreferredSize(new Dimension(1280, 720));
        panel.setBackground(new Color(89, 108, 171, 255));

        JFrame frame = new JFrame("Test");
        frame.setLocation(100, 100);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(panel);
        frame.pack();
        frame.setVisible(true);

        panel.addComponentListener(new ComponentAdapter()
        {
            @Override
            public void componentResized(ComponentEvent e)
            {
                int targetWidth = frame.getSize().width;
                int targetHeight = frame.getSize().width * 9 / 16;

                if (targetHeight > frame.getSize().height)
                {
                    targetHeight = frame.getSize().height;
                    targetWidth = frame.getSize().height * 16 / 9;
                }

                frame.setSize(targetWidth, targetHeight);
            }
        }); 
    }
}

Solution

This is my idea.

JPanel panel = new JPanel();
    panel.setPreferredSize(new Dimension(1280, 720));
    panel.setBackground(new Color(89, 108, 171, 255));

    JFrame frame = new JFrame("Test");
    frame.setLocation(100, 100);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JPanel p2 = new JPanel();
    p2.add(panel);
    frame.setContentPane(p2);
    frame.pack();
    frame.setVisible(true);

    p2.addComponentListener(new ComponentAdapter()
    {
        @Override
        public void componentResized(ComponentEvent e)
        {
            int fw = frame.getSize().width;
            int fh = frame.getSize().height;
            if( 16*fh > 9*fw ){
                panel.setPreferredSize( new Dimension(fw, 9*fw/16) );
            } else{
                Dimension d = new Dimension(16*fh/9, fh);
                panel.setPreferredSize( d );
            }

            frame.validate();
        }
    });

This way you don't change the value that the user is adjusting. (size of the frame) You are responding to changes and making sure the panel is still the correct size.

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