GridBagLayout-如何使此单元格填充其下方的空间？

Question

I'm creating a JFrame with 4 JPanels. Using GridBagLayout, I create three rows and two columns, two panels per column. By changing the blue panel's cellheight from 1 to 2 I can make it cover the cell below it. I'd like to do the same for the green panel, to fill the space below it. Here's what my code currently produces:

I tried changing the green panel's gridheight to 2 but I end up with this:

Am I using GridBagLayout incorrectly? What is the appropriate way of doing this?

Here's my code:

import java.awt.Color;
import java.awt.Container;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Main {

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        addComponents(frame.getContentPane());
        frame.setSize(800, 600);
        frame.setVisible(true);
    }

    public static void addComponents(Container contentPane) {
        contentPane.setLayout(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();
        c.insets = new Insets(3,3,3,3);
        c.fill = GridBagConstraints.BOTH;

        c.gridx = 0;
        c.gridy = 0;
        c.gridwidth = 1;
        c.gridheight = 2;
        c.weightx = 1;
        c.weighty = 0.85;
        JPanel panel1 = new JPanel();
        panel1.setBackground(Color.BLUE);
        contentPane.add(panel1, c);

        c.gridx = 0;
        c.gridy = 2;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.weightx = 1.1;
        c.weighty = 0.35;
        JPanel panel2 = new JPanel();
        panel2.setBackground(Color.YELLOW);
        contentPane.add(panel2, c);

        c.gridx = 1;
        c.gridy = 0;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.weightx = 0.15;
        c.weighty = 0.5;
        JPanel panel3 = new JPanel();
        panel3.setBackground(Color.RED);
        contentPane.add(panel3, c);

        c.gridx = 1;
        c.gridy = 1;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.weightx = 0.38;
        c.weighty = 0.5;
        JPanel panel4 = new JPanel();
        panel4.setBackground(Color.GREEN);
        contentPane.add(panel4, c);
    }
}

Answer 1

I create three rows and two columns,

Actually you only have two rows, since you only ever add components with a gridy value of 0 and 1. The fact that one of the components has a gridheight of 2 doesn't create a new row.

One solution is to use nested panels.

Create a panel for the blue and yellow components. This would use a GridBagLayout with one column and 2 rows. You then set the weighty values for each component to give your desired height.

Then you create a second panel for the red and green components again with 1 column and two rows. The weighty would be set to 0.5 for each.

Finally you create a third panel with 2 columns and one row. You set the desired weightx and add the above two panels to this panel and then add the panel to the frame.

Answer 2

The layout starts to behave as expected if there is a 3rd column of three cells, each with a row span of 1.

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

public class AnotherFourPanelLayout {

    private JComponent ui = null;

    AnotherFourPanelLayout() {
        initUI();
    }

    public void initUI() {
        if (ui != null) {
            return;
        }

        ui = new JPanel(new BorderLayout(4, 4));
        ui.setBorder(new EmptyBorder(4, 4, 4, 4));

        addComponents(ui);
    }

    public void addComponents(Container contentPane) {
        contentPane.setLayout(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();
        c.insets = new Insets(3, 3, 3, 3);
        c.fill = GridBagConstraints.BOTH;

        c.gridx = 0;
        c.gridy = 0;
        c.gridwidth = 1;
        c.gridheight = 2;
        c.weightx = 0.66;
        c.weighty = 0.66;
        JPanel panel1 = new JPanel();
        addLabel(panel1, c);
        panel1.setBackground(Color.CYAN);
        contentPane.add(panel1, c);

        c.gridx = 0;
        c.gridy = 2;
        c.gridwidth = 1;
        c.gridheight = 1;
        //c.weightx = 1.1; // logical?
        c.weightx = 0.66; 
        c.weighty = 0.33;
        JPanel panel2 = new JPanel();
        addLabel(panel2, c);
        panel2.setBackground(Color.YELLOW);
        contentPane.add(panel2, c);

        c.gridx = 1;
        c.gridy = 0;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.weightx = 0.33;
        c.weighty = 0.33;
        JPanel panel3 = new JPanel();
        addLabel(panel3, c);
        panel3.setBackground(Color.RED);
        contentPane.add(panel3, c);

        c.gridx = 1;
        c.gridy = 1;
        c.gridwidth = 1;
        c.gridheight = 2;
        c.weightx = 0.33;
        c.weighty = 0.66;
        JPanel panel4 = new JPanel();
        addLabel(panel4, c);
        panel4.setBackground(Color.GREEN);
        contentPane.add(panel4, c);

        // hack to fix?
        c.gridx = 2;
        c.gridy = 0;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.weightx = 0.01;
        c.weighty = 0.33;
        JPanel panelH1 = new JPanel();
        //addLabel(panelH1, c);
        panelH1.setBackground(Color.MAGENTA);
        contentPane.add(panelH1, c);

        c.gridy = 1;
        JPanel panelH2 = new JPanel();
        //addLabel(panelH2, c);
        panelH2.setBackground(Color.MAGENTA);
        contentPane.add(panelH2, c);

        c.gridy = 2;
        JPanel panelH3 = new JPanel();
        //addLabel(panelH3, c);
        panelH3.setBackground(Color.MAGENTA);
        contentPane.add(panelH3, c);
    }

    private void addLabel(JPanel panel, GridBagConstraints gbc) {
        panel.add(new JLabel(constraintsToString(gbc)));
    }

    private String constraintsToString(GridBagConstraints gbc) {
        StringBuilder sb = new StringBuilder();

        sb.append("<html><table>");
        sb.append(addRowToTable("Grid X", gbc.gridx));
        sb.append(addRowToTable("Grid Y", gbc.gridy));
        sb.append(addRowToTable("Weight X", gbc.weightx));
        sb.append(addRowToTable("Weight Y", gbc.weighty));
        sb.append(addRowToTable("Grid Width", gbc.gridwidth));
        sb.append(addRowToTable("Grid Height", gbc.gridheight));

        return sb.toString();
    }

    private String addRowToTable(String label, double value) {
        StringBuilder sb = new StringBuilder("<tr><td>");

        sb.append(label);
        sb.append("</td><td>");
        sb.append(value);
        sb.append("</td></tr>");


        return sb.toString();
    }

    public JComponent getUI() {
        return ui;
    }

    public static void main(String[] args) {
        Runnable r = new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (Exception useDefault) {
                }
                AnotherFourPanelLayout o = new AnotherFourPanelLayout();

                JFrame f = new JFrame(o.getClass().getSimpleName());
                f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                f.setLocationByPlatform(true);

                f.setContentPane(o.getUI());
                f.pack();
                f.setMinimumSize(f.getSize());

                f.setVisible(true);
            }
        };
        SwingUtilities.invokeLater(r);
    }
}