在 JPanel 上使用 GridBagLayout 并将 JButton 放入其中时遇到问题

Question

这就是我所拥有的。我有两个 JPanel，每个都有 GridBagLayout。它们的权重 x = 0.5 并填充两个方向。所以基本上窗口是一个 JPanel 的一半，另一个 JPanel 的一半。它应该保持这种状态。但是，如果我将 JButton 放入其中一个，则 JPanel 会变宽并占用第二个 JPanel 的一些空间。

我应该怎样做才能防止这种行为？是否还有其他布局可以按照我描述的方式工作？

这是我一直在测试的代码。

`

JFrame f = new JFrame();
        f.setLayout(new BorderLayout());
        f.setTitle("Start Window");
        f.setDefaultCloseOperation(f.EXIT_ON_CLOSE);
        f.setSize(400,300);
        f.setResizable(true);

        JPanel top = new JPanel();
        JPanel right = new JPanel();
        JPanel bottom = new JPanel();
        JPanel left = new JPanel();

        top.setPreferredSize(new Dimension(30,30));
        right.setPreferredSize(new Dimension(30,30));
        bottom.setPreferredSize(new Dimension(30,30));
        left.setPreferredSize(new Dimension(30,30));

        f.add(top,BorderLayout.NORTH);
        f.add(right,BorderLayout.EAST);
        f.add(bottom,BorderLayout.SOUTH);
        f.add(left,BorderLayout.WEST);

        JPanel centerContainer = new JPanel(new GridBagLayout());
        GridBagConstraints centerLayout = new GridBagConstraints();
        centerContainer.setBackground(Color.blue);
        f.add(centerContainer);

        JPanel centerLeft = new JPanel(new GridBagLayout());
        GridBagConstraints centerLeftLayout = new GridBagConstraints();
        centerLayout.gridx=0;
        centerLayout.gridy=0;
        centerLayout.weightx=0.5;
        centerLayout.weighty=1;
        centerLayout.fill = GridBagConstraints.BOTH;
        centerLeft.setBackground(Color.red);
        centerContainer.add(centerLeft,centerLayout);

        JPanel centerRight = new JPanel();
        centerLayout.gridx=1;
        centerLayout.gridy=0;
        centerLayout.weightx=0.5;
        centerLayout.weighty=1;
        centerLayout.fill = GridBagConstraints.BOTH;
        centerRight.setBackground(Color.green);
        centerContainer.add(centerRight,centerLayout);

        JPanel leftElement = new JPanel(new GridBagLayout());
        GridBagConstraints leftElementLayout = new GridBagConstraints();

        centerLeftLayout.gridx=0;
        centerLeftLayout.gridy=0;
        centerLeftLayout.weightx=1;
        centerLeftLayout.weighty=1;
        centerLeftLayout.fill = GridBagConstraints.HORIZONTAL;

        centerLeft.add(leftElement,centerLeftLayout);

        JButton leftBtn = new JButton("CLIIIIICK!!!");
        leftBtn.setLayout(new GridBagLayout());
        leftElementLayout.gridx=0;
        leftElementLayout.gridy=0;
        leftElementLayout.weighty=0;
        leftElementLayout.weightx=1;
        leftElementLayout.fill=GridBagConstraints.HORIZONTAL;


        leftElement.add(leftBtn,leftElementLayout);


        f.setVisible(true);

`

Answer 1

解决方案：需要时使用更简单的布局。在这里，最好将这些中心 JPanel 保存在 1 行 2 列的 GridLayout 中，因为这将保证它们将面板精确地分成两部分。

旁注：

• 没有必要（或没有意义）给 JButton 一个布局管理器，除非你要向它添加组件，这将是一个不寻常的事情，但我见过这样做，尽管很少。
• 如果您想要组件周围有 30 像素的边框，请使用空边框：

int ebGap = 30;
setBorder(BorderFactory.createEmptyBorder(ebGap, ebGap, ebGap, ebGap));

例如：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import javax.swing.*;

@SuppressWarnings("serial")
public class SwingFoo02 extends JPanel {
    
    private static final int PREF_W = 400;
    private static final int PREF_H = 300;
    
    public SwingFoo02() {
        int ebGap = 30;
        setBorder(BorderFactory.createEmptyBorder(ebGap, ebGap, ebGap, ebGap));
        
        JPanel centerLeft = new JPanel(new GridBagLayout());
        JPanel centerRight = new JPanel();
        
        centerLeft.setBackground(Color.RED);
        centerRight.setBackground(Color.GREEN);        

        JButton leftBtn = new JButton("CLIIIIICK!!!");
        GridBagConstraints gbc = new GridBagConstraints();        
        gbc.anchor = GridBagConstraints.CENTER;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.weightx = 1.0;
        gbc.weighty = 0.0;
        gbc.gridx = 1;
        gbc.gridy = 1;
        centerLeft.add(leftBtn, gbc);
        
        setLayout(new GridLayout(1, 2));
        add(centerLeft);
        add(centerRight);

    }
    

    @Override
    public Dimension getPreferredSize() {
        Dimension supSize = super.getPreferredSize();
        int w = Math.max(supSize.width, PREF_W);
        int h = Math.max(supSize.height, PREF_H);
        return new Dimension(w, h);
    }
    
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            SwingFoo02 mainPanel = new SwingFoo02();

            JFrame frame = new JFrame("GUI");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.add(mainPanel);
            frame.pack();
            frame.setLocationRelativeTo(null);
            frame.setVisible(true);
        });
    }

}