網格包布局25P%%

這是防止 GridBagLayout 單元格相對于其內容調整大小的正確方法嗎？

gbl_panel.columnWidths = new int[] {1000, 4000, 1000};

SSCCE

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;

import javax.swing.AbstractListModel;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.border.EmptyBorder;

public class GridBagLayoutTemplate extends JFrame {

private JPanel contentPane;

public GridBagLayoutTemplate() {
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(100, 100, 450, 300);
    contentPane = new JPanel();
    contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
    contentPane.setLayout(new BorderLayout(0, 0));
    setContentPane(contentPane);


    JPanel panel = new JPanel();
    contentPane.add(panel);

    GridBagLayout gbl_panel = new GridBagLayout();
    gbl_panel.rowHeights = new int[] {1};
    gbl_panel.columnWidths = new int[] {1000, 4000, 1000};
    gbl_panel.columnWeights = new double[]{1.0, 4.0, 1.0};
    gbl_panel.rowWeights = new double[]{1.0};
    panel.setLayout(gbl_panel);

    JScrollPane scrollPane = new JScrollPane();
    GridBagConstraints gbc_scrollPane = new GridBagConstraints();
    gbc_scrollPane.insets = new Insets(0, 0, 0, 5);
    gbc_scrollPane.fill = GridBagConstraints.BOTH;
    gbc_scrollPane.gridx = 0;
    gbc_scrollPane.gridy = 0;
    panel.add(scrollPane, gbc_scrollPane);

    JList list = new JList();
    scrollPane.setViewportView(list);
    list.setModel(new AbstractListModel() {
        String[] values = new String[] {"qwe"};
        public int getSize() {
            return values.length;
        }
        public Object getElementAt(int index) {
            return values[index];
        }
    });

    JScrollPane scrollPane_1 = new JScrollPane();
    GridBagConstraints gbc_scrollPane_1 = new GridBagConstraints();
    gbc_scrollPane_1.insets = new Insets(0, 0, 0, 5);
    gbc_scrollPane_1.fill = GridBagConstraints.BOTH;
    gbc_scrollPane_1.gridx = 1;
    gbc_scrollPane_1.gridy = 0;
    panel.add(scrollPane_1, gbc_scrollPane_1);

    JList list_1 = new JList();
    scrollPane_1.setViewportView(list_1);
    list_1.setModel(new AbstractListModel() {
        String[] values = new String[] {"qwe"};
        public int getSize() {
            return values.length;
        }
        public Object getElementAt(int index) {
            return values[index];
        }
    });

    JScrollPane scrollPane_2 = new JScrollPane();
    GridBagConstraints gbc_scrollPane_2 = new GridBagConstraints();
    gbc_scrollPane_2.fill = GridBagConstraints.BOTH;
    gbc_scrollPane_2.gridx = 2;
    gbc_scrollPane_2.gridy = 0;
    panel.add(scrollPane_2, gbc_scrollPane_2);

    JList list_3 = new JList();
    scrollPane_2.setViewportView(list_3);
    list_3.setModel(new AbstractListModel() {
        String[] values = new String[] {"qweqweqweqweqwqweqweqweqweqweqweqweqweqwqweqweqweqweqweqweqweqwqweqweqweqweqweqweqweqweqwqweqweqweqweqweqweqweqweqwqweqweqweqweqwqweqweqweqweqweqweqweqweqwqweqweqweqweqweqweqweqweqwqweqweqweqwe"};
        public int getSize() {
            return values.length;
        }
        public Object getElementAt(int index) {
            return values[index];
        }
    });
}
}

public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                GridBagLayoutTemplate frame = new GridBagLayoutTemplate();
                frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

uj5u.com熱心網友回復：

有趣的。我以前從未見過這樣的方法。

通常使用 GridBagLayout 以便：

1. 每個組件都根據其首選大小分配空間
2. 如果有額外空間可用，則根據分配給每個組件的 weightx（權重）值將空間分配給每個組件。

因此，僅以 25% 50% 25% 的比例分配額外的空間。

您的方法似乎忽略了組件的首選大小，并以 25% 50% 25% 的比例分配空間。

但是，您首先需要進行以下更改以獲得正確的比率：

//gbl_panel.columnWidths = new int[] {1000, 4000, 1000};
//gbl_panel.columnWeights = new double[]{1.0, 4.0, 1.0};
gbl_panel.columnWidths = new int[] {1000, 2000, 1000};
gbl_panel.columnWeights = new double[]{1.0, 2.0, 1.0};

下面是我用來測驗在 400 像素寬的面板上為組件分配空間的簡化代碼：

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

public class GridBagLayoutRelative extends JPanel
{
    public GridBagLayoutRelative()
    {
        setPreferredSize( new Dimension(400, 300) );

        //  Components will be allocated relative widths of 25%, 50%, 25%
        //  (preferred width will be ignored)

        GridBagLayout gbl = new GridBagLayout();
        //gbl.columnWidths = new int[] {25, 50, 25}; // doesn't work
        gbl.columnWidths = new int[] {250, 500, 250}; // larger value in same ratio
        gbl.columnWeights = new double[] {25.0, 50.0, 25.0};
        setLayout(gbl);

        GridBagConstraints gbc = new GridBagConstraints();
        gbc.fill = GridBagConstraints.BOTH;
        gbc.weighty = 1.0;
        gbc.gridy = 0;

        JPanel red = new JPanel();
        red.setBackground( Color.RED );
        red.setPreferredSize( new Dimension(30, 200) );
        gbc.gridx = 0;
        add(red, gbc);

        JPanel green = new JPanel();
        green.setBackground( Color.GREEN );
        green.setPreferredSize( new Dimension(40, 200) );
        gbc.gridx = 1;
        add(green, gbc);

        JPanel blue = new JPanel();
        blue.setBackground( Color.BLUE );
        blue.setPreferredSize( new Dimension(50, 200) );
        gbc.gridx = 2;
        add(blue, gbc);

        addComponentListener( new ComponentAdapter()
        {
            @Override
            public void componentResized(ComponentEvent e)
            {
                System.out.println( e.getComponent().getSize() );

                for (Component c: getComponents())
                    System.out.println( "\t"   c.getSize() );
            }
        });
    }

    private static void createAndShowGUI()
    {
        JFrame frame = new JFrame("GridBagLayout Relative");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(new GridBagLayoutRelative());
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationByPlatform( true );
        frame.setVisible( true );
    }

    public static void main(String[] args) throws Exception
    {
        java.awt.EventQueue.invokeLater( () -> createAndShowGUI() );
    }
}

結果是：

java.awt.Dimension[width=100,height=300]
java.awt.Dimension[width=200,height=300]
java.awt.Dimension[width=100,height=300]

所以我會說這種方法有效。

注意：如果您有興趣，過去我曾建議您可以使用專為此類布局設計且更易于使用的相對布局。

使用RelativeLayout上述行為將通過使用復制：

RelativeLayout rl = new RelativeLayout(RelativeLayout.X_AXIS);
rl.setFill(true);
setLayout( rl );

JPanel red = new JPanel();
red.setBackground( Color.RED );
red.setPreferredSize( new Dimension(30, 200) );
add(red, new Float(25));

JPanel green = new JPanel();
green.setBackground( Color.GREEN );
green.setPreferredSize( new Dimension(40, 200) );
add(green, new Float(50));

JPanel blue = new JPanel();
blue.setBackground( Color.BLUE );
blue.setPreferredSize( new Dimension(50, 200) );
add(blue, new Float(25));

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