如何获得 GridBagLayout 来排列列宽？

Question

这是一个非常简单的布局（包括代码），其中不均匀的列大小可以改善填充。

有没有办法使用单个 GridBagLayout 让组件很好地组合在一起？

我认为对前两个组件使用 3 的宽度，然后对接下来的两行使用 5 和 1 的宽度会影响对齐，但我无法让它保持齐平。我目前的解决方案（不包括在内）是创建一个带有红色和绿色面板的子面板。

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

public class GridBagWrong{
    public static void main(String[] args){
        JPanel content = new JPanel(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        //create five panels to layout.
        JPanel a = new JPanel();
        a.setPreferredSize( new Dimension(300, 30) );
        a.setBorder( BorderFactory.createLineBorder(Color.BLUE) );
        JPanel b = new JPanel();
        b.setPreferredSize( new Dimension(300, 30) );
        b.setBorder( BorderFactory.createLineBorder(Color.BLUE) );
        JPanel c = new JPanel();
        c.setPreferredSize( new Dimension(500, 30) );
        c.setBorder( BorderFactory.createLineBorder(Color.GREEN) );
        JPanel d = new JPanel();
        d.setPreferredSize( new Dimension(500, 30) );
        d.setBorder( BorderFactory.createLineBorder(Color.GREEN) );
        JPanel e = new JPanel();
        e.setPreferredSize( new Dimension(100, 60) );
        e.setBorder( BorderFactory.createLineBorder(Color.RED) );
        //place them in a gridbaglayout.
        gbc.gridwidth = 3;
        content.add(a, gbc);
        gbc.gridx = 3;
        content.add(b, gbc);
        gbc.gridx = 0;
        gbc.gridy = 1;
        gbc.gridwidth = 5;
        content.add(c, gbc);
        gbc.gridy = 2;
        content.add(d, gbc);
        
        gbc.gridy = 1;
        gbc.gridx = 5;
        gbc.gridheight = 2;
        gbc.gridwidth = 1;
        content.add(e, gbc);
        
        JFrame frame = new JFrame("test");        
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.setContentPane( content );
        frame.pack();
        frame.setVisible(true);
    }

}

Answer 1

您可以使用上面的评论跟进我的评论：

//JPanel content = new JPanel(new GridBagLayout());
GridBagLayout gbl = new GridBagLayout();
int[] columns = new int[6];
Arrays.fill(columns, 100);
gbl.columnWidths = columns;
JPanel content = new JPanel(gbl);

上面的代码说明 6 列中的每一列的最小宽度为 100。

如果将组件添加到具有gridwidth = 1 的列中，则该组件的首选大小将用作列的宽度。

所以现在当您指定gridwidth = 3 时，它是有意义的，因为布局可以使用添加到列的组件的宽度或最小宽度来确定组件的实际大小。

Answer 2

出于某种原因，GridBagLayout 正在为其计算添加额外空间，但我不知道为什么。一开始我以为是LineBorder，但是当我修改你的代码去掉边框的时候，还是不行……

我不知道右边多余的间距是从哪里来的（可能真的很明显，但我看不到）

Sooo，这是我“翻转桌子”和“愤怒”而不是“破解它”的那些时刻之一

由于第一行和第二行之间似乎存在脱节，出于某种原因，我将第一行的两个面板合并为一个面板，并摆脱了所有gridwidths（或多或少）

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            //create five panels to layout.
            JPanel a = new LayoutPane();
            a.setForeground(Color.BLUE);
            a.setPreferredSize(new Dimension(300, 30));

            JPanel b = new LayoutPane();
            b.setPreferredSize(new Dimension(300, 30));
            b.setForeground(Color.BLUE);

            JPanel c = new LayoutPane();
            c.setPreferredSize(new Dimension(500, 30));
            c.setForeground(Color.GREEN);

            JPanel d = new LayoutPane();
            d.setPreferredSize(new Dimension(500, 30));
            d.setForeground(Color.GREEN);

            JPanel e = new LayoutPane();
            e.setPreferredSize(new Dimension(100, 60));
            e.setForeground(Color.RED);

            JPanel topPane = new JPanel(new GridBagLayout());

            //place them in a gridbaglayout.
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.fill = GridBagConstraints.HORIZONTAL;            
            topPane.add(a, gbc);
            gbc.gridx++;
            topPane.add(b, gbc);

            gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.fill = GridBagConstraints.HORIZONTAL;            
            add(topPane, gbc);


            gbc = new GridBagConstraints();
            gbc.gridx = 0;
            gbc.gridy = 1;
            gbc.anchor = GridBagConstraints.WEST;
            add(c, gbc);

            gbc.gridy = 2;
            add(d, gbc);

            gbc = new GridBagConstraints();
            gbc.gridy = 1;
            gbc.gridx++;
            gbc.gridheight = 2;
            gbc.anchor = GridBagConstraints.EAST;
            add(e, gbc);
        }

    }

    public class LayoutPane extends JPanel {

        public LayoutPane() {
            setOpaque(false);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(getForeground());
            g2d.drawRect(0, 0, getWidth() - 1, getHeight() - 1);
            String text = getWidth() + "x" + getHeight();
            FontMetrics fm = g2d.getFontMetrics();
            int x = (getWidth() - fm.stringWidth(text)) / 2;
            int y = ((getHeight() - fm.getHeight()) / 2) + fm.getAscent();
            g2d.drawString(text, x, y);
            g2d.dispose();
        }

    }
}