面板占用相等的空间答案

【问题标题】：Panels take equal space面板占用相等的空间
【发布时间】：2017-12-24 13:20:52
【问题描述】：

我有两个面板。第一个看起来像这样。

public class BoardPanel extends JPanel
{
    public BoardPanel()
    {
         setLayout(null);
         this.setOpaque(false);

        Button button = new JButton("..");
        button.setLocation(...);
        button.setSize(...);
        add(button);
    }

    public void paintComponent( Graphics g )
    {
        /*
        * Painting some stuff here. 
        */
    }   
}

另一个面板是这样的：

public class OtherPanel extends JPanel
{
    public OtherPanel()
    {
        super();
        this.setLayout(null);
        this.setOpaque(false);

        JPanel panel1 = new JPanel();
        panel1.setLocation(...);
        panel1.setSize(...);
        panel1.setOpaque( .. );

        JPanel panel2 = new JPanel();
        panel2.setLocation(...);
        panel2.setSize(...);
        panel2.setOpaque( .. );

        add(panel1):
        add(panel2);
    }   

}

之后，我将两个面板放在一个框架中。但我希望我的 BoardPanel 比 OtherPanel 占用更多的屏幕。所以我用 GridBagLayout 作为框架

public class MainFrame extends JFrame
{ 
    private GridBagLayout aGridLayout = new GridBagLayout();
    private GridBagConstraints constraints = new GridBagConstraints();

    public MainFrame()
    {
        super("Quoridor");
        setLayout(gridLayout);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(1366, 768);
        setVisible(true);
        setResizable(false);
        this.getContentPane().setBackground(Color.decode("#b2a6a6"));

        BoardPanel boardPanel = new BoardPanel();
        OtherPanel otherPanel = new OtherPanel();

        this.addComponent(boardPanel, 1, 1, 2, 1);
        this.addComponent(otherPanel, 1, 3, 1, 1);
    }

    public void addComponent(Component component , int row , int column , int width
            , int height)
    {
        constraints.gridx = column;
        constraints.gridy = row;
        constraints.gridwidth = width;
        constraints.gridheight = height;
        aGridLayout.setConstraints(component, constraints);
        add(component);
    }
}

问题是，框架为两个面板提供了相等的空间，而没有为 boardPanel 提供更多空间。为什么会这样？它与面板的边界有关吗？

【问题讨论】：

标签： java layout panel frame gridbaglayout

【解决方案1】：

这里有一个很好的 GridBagLayout 教程：https://docs.oracle.com/javase/tutorial/uiswing/layout/gridbag.html。另请参阅下面的代码和屏幕截图。锚字段将组件定位在第一行。 weightx 字段为 boardPanel 的列提供了更多空间。 ipady 字段指定要添加到组件高度的多少。在这里，boardPanel 获得了大部分的宽度和所有的高度。 otherPanel 面板获得一半的高度。

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

public class GridExample {
    private JFrame mainFrame;
    private JPanel boardPanel, otherPanel;

    public GridExample(){
        mainFrame = new JFrame();
        mainFrame.setSize(600,400);
        mainFrame.setLayout(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();

        mainFrame.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent windowEvent){
                System.exit(0);
            }        
        });    

        boardPanel = new JPanel();
        boardPanel.add(new JLabel("board panel"));
        boardPanel.setBackground(Color.yellow);

        otherPanel = new JPanel();
        otherPanel.add(new JLabel("other panel"));
        otherPanel.setBackground(Color.green);

        c.anchor = GridBagConstraints.FIRST_LINE_START;
        c.fill = GridBagConstraints.HORIZONTAL;
        c.weightx = 0.75;
        c.ipady = 400;
        c.gridx = 0;
        c.gridy = 0;
        mainFrame.add(boardPanel, c);

        c.anchor = GridBagConstraints.FIRST_LINE_START;
        c.fill = GridBagConstraints.HORIZONTAL;
        c.weightx = 0.25;
        c.ipady = 200;
        c.gridx = 1;
        c.gridy = 0;    
        mainFrame.add(otherPanel, c);
        mainFrame.setVisible(true);  
    }

    public static void main(String[] args){
        GridExample  swingContainerDemo = new GridExample();  
    }
}

【讨论】：