Java:如何控制JPanel长宽比？

Question

我有一个JPanel我想要保持正方形但是我希望它的大小,以便它填充其父JFrame中可能的最大空间量但仍保持正方形,即它采用JFrame的最短边作为方形宽度.

我搜索了网络,检查了所有布局管理器,似乎没有一个简单的解决方案来解决这个非常简单的问题.

Answer 1

import java.awt.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;

public class YouAreSoSquare {

    private static JPanel createPanel() {
        // GBL is important for the next step..
        JPanel gui = new JPanel(new GridBagLayout());
        JPanel squareComponent = new JPanel() {
            private static final long serialVersionUID = 1L;
            @Override
            public Dimension getPreferredSize() {
                // Relies on being the only component
                // in a layout that will center it without
                // expanding it to fill all the space.
                Dimension d = this.getParent().getSize();
                int newSize = d.width > d.height ? d.height : d.width;
                newSize = newSize == 0 ? 100 : newSize;
                return new Dimension(newSize, newSize);
            }
        };
        squareComponent.setBackground(Color.RED);
        gui.add(squareComponent);
        return gui;
    }

    public static void main(String[] args) {
        Runnable r = new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (Exception useDefault) {
                }
                JFrame mainFrame = new JFrame("..So Square");
                mainFrame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                mainFrame.setLocationByPlatform(true);
                mainFrame.add(createPanel());
                mainFrame.pack();
                mainFrame.setMinimumSize(mainFrame.getSize());
                mainFrame.setVisible(true);
            }
        };
        SwingUtilities.invokeLater(r);
    }
}