How to maintain the aspect ratio of the screen after being resized by the user?

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How to maintain the aspect ratio of the screen after being resized by the user?

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I need to restrict a certain proportion of a JFrame so that the layout of what I want to display on it is not distorted, but I would not want to have to block resize with setRezisable() . The minimum aspect ratio for testing is 350x500 (7:10 ratio), but I would like to keep that ratio every time the screen changes size.

I've done an example to see how it looks:

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;

import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class KeepAspectRatioTest extends JFrame {

    private static final long serialVersionUID = 1L;

    private static final int WIDTH = 350;
    private static final int HEIGHT = 500;

    public static void main(String[] args) {

        SwingUtilities.invokeLater(() -> {

            KeepAspectRatioTest screen = new KeepAspectRatioTest();
            screen.setVisible(true);
        });
    }

    public KeepAspectRatioTest() {

        initUI();
    }

    private void initUI() {

        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setPreferredSize(new Dimension(WIDTH, HEIGHT));
        setTitle("Keep Aspect Ratio");

        JPanel board = new JPanel();
        board.setBorder(BorderFactory.createMatteBorder(1, 1, 1, 1, Color.black));


        JPanel sidePanel = new JPanel();
        sidePanel.setBorder(BorderFactory.createMatteBorder(1, 1, 1, 1, Color.red));
        sidePanel.setLayout(new BoxLayout(sidePanel, BoxLayout.Y_AXIS));
        sidePanel.setPreferredSize(new Dimension(WIDTH/6, HEIGHT));

        add(board, BorderLayout.CENTER);
        add(sidePanel, BorderLayout.EAST);

        pack();
        setLocationRelativeTo(null);

    }
}

How do I keep the aspect ratio of the screen after resizing?

Q: I think I need to use a ComponentListener , I just do not know how to control it with this listener, especially since, by allowing resizing, it is also enabled to maximize the screen.

java swing jframe redimensionamento

asked by anonymous 29.09.2017 / 13:06

1 answer

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score 0 · Answer 1

You can use componentResized of componentListener to perform the calculation according to ratio . Remember that the ratio is 10: 7 or approximately 1.42 to stay horizontal or 7:10 = 0.7 to stay vertical. Works for conteiners and painels . Ex:

public class AspectRatio {
    static final double RATIO = 0.7;
    public static void main(String[] args) {
        final JPanel innerPanel = new JPanel();
        innerPanel.setBackground(Color.BLUE);

        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, 800);
        frame.setVisible(true);
    }

    private static void resizePreview(JPanel innerPanel, JPanel container) {
        int width = container.getWidth();
        int height = container.getHeight();
        float currentAspectRatio = (float) width / height;

        if (currentAspectRatio > RATIO) {
                 width = (int) (height * RATIO);
        } else {
                 height = (int) (width / RATIO);
        }
        innerPanel.setPreferredSize(new Dimension(width, height));
        container.revalidate();
    }
}

If you want to keep the Jframe aspect itself, you need to override the paint() method of JFrame , but will work only if it is resized by the corners. Remember that it is not a good approximation, since the user should have total control over the resizing of the window, which should keep the aspect is the content inside it:

public class AspectRatio {
    static final double RATIO = 1.42;
    static JFrame frame;
    public static void main(String[] args) {
        final JPanel innerPanel = new JPanel();
        innerPanel.setBackground(Color.BLUE);

        final JPanel container = new JPanel(new GridBagLayout());
        container.add(innerPanel);

        frame = new JFrame("AspectRatio") {
            public void paint(Graphics g) {
                super.paint(g);
                resizePreview(frame);
            };
        };
        frame.getContentPane().add(container);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 600);
        frame.setVisible(true);
    }

    private static void resizePreview(JFrame jFrame) {
        int width = jFrame.getWidth();
        int height = jFrame.getHeight();
        float currentAspectRatio = (float) width / height;

        if (currentAspectRatio > RATIO) {
            width = (int) (height * RATIO);
        } else {
            height = (int) (width / RATIO);
        }
        jFrame.setSize(new Dimension(width, height));
        jFrame.revalidate();
        jFrame.repaint();
    }
}

I hope I have helped!