在 Swing GUI 中提供空白

没有空白的 GUI 显得“拥挤”。如何在不显式设置组件位置或大小的情况下提供空白？

使用各种LayoutManagers可以在各个组件之间提供间距。

1.) 边框布局：

• 重载构造函数： BorderLayout（int水平间隙，int垂直间隙） http://docs.oracle.com/javase/7/docs/api/java/awt/BorderLayout.html#BorderLayout%28int,%20int%29

• Getter 和 Setter 方法

  对于水平间距: BorderLayout.getHgap() http://docs.oracle.com/javase/7/docs/api/java/awt/BorderLayout.html#getHgap%28%29 and BorderLayout.setHgap(int hgap) http://docs.oracle.com/javase/7/docs/api/java/awt/BorderLayout.html#setHgap%28int%29

  对于垂直间距: BorderLayout.getVgap() http://docs.oracle.com/javase/7/docs/api/java/awt/BorderLayout.html#getVgap%28%29 and BorderLayout.setVgap() http://docs.oracle.com/javase/7/docs/api/java/awt/BorderLayout.html#setVgap%28int%29

2.) 流程布局：

• 重载构造函数： FlowLayout（int对齐，int hgap，int vgap） http://docs.oracle.com/javase/7/docs/api/java/awt/FlowLayout.html#FlowLayout%28int,%20int,%20int%29

• Getter 和 Setter 方法

  对于水平间距: FlowLayout.getHgap() http://docs.oracle.com/javase/7/docs/api/java/awt/FlowLayout.html#getHgap%28%29 and FlowLayout.setHgap(int hgap) http://docs.oracle.com/javase/7/docs/api/java/awt/FlowLayout.html#setHgap%28int%29

  对于垂直间距: FlowLayout.getVgap() http://docs.oracle.com/javase/7/docs/api/java/awt/FlowLayout.html#getVgap() and FlowLayout.setVgap() http://docs.oracle.com/javase/7/docs/api/java/awt/FlowLayout.html#setVgap(int)

3.) 网格布局：

• 重载构造函数： GridLayout（int行，int列，int hgap，int vgap） http://docs.oracle.com/javase/7/docs/api/java/awt/GridLayout.html#GridLayout%28int,%20int,%20int,%20int%29

• Getter 和 Setter 方法

  对于水平间距: GridLayout.getHgap() http://docs.oracle.com/javase/7/docs/api/java/awt/GridLayout.html#getHgap() and GridLayout.setHgap(int hgap) http://docs.oracle.com/javase/7/docs/api/java/awt/GridLayout.html#setHgap(int)

  对于垂直间距: GridLayout.getVgap() http://docs.oracle.com/javase/7/docs/api/java/awt/GridLayout.html#getVgap() and GridLayout.setVgap() http://docs.oracle.com/javase/7/docs/api/java/awt/GridLayout.html#setVgap(int)

4.) GridBagLayout :

GridBagConstraints.insets http://docs.oracle.com/javase/7/docs/api/java/awt/GridBagConstraints.html#insets

5.) 卡片布局 (example http://docs.oracle.com/javase/7/docs/api/java/awt/GridLayout.html#setHgap(int)) :

CardLayout(int hGap, int vGap) http://docs.oracle.com/javase/7/docs/api/java/awt/GridLayout.html#getVgap()

显示所有正在运行的构造函数的示例：

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

public class LayoutExample {

    private final int hGap = 5;
    private final int vGap = 5;

    private String[] borderConstraints = {
        BorderLayout.PAGE_START,
        BorderLayout.LINE_START,
        BorderLayout.CENTER,
        BorderLayout.LINE_END,
        BorderLayout.PAGE_END
    };

    private JButton[] buttons;

    private GridBagConstraints gbc;

    private JPanel borderPanel;
    private JPanel flowPanel;
    private JPanel gridPanel;
    private JPanel gridBagPanel;
    private JPanel cardPanel;

    public LayoutExample() {
        buttons = new JButton[16];
        gbc = new GridBagConstraints();
        gbc.anchor = GridBagConstraints.FIRST_LINE_START;   
        gbc.insets = new Insets(hGap, vGap, hGap, vGap);        
    }

    private void displayGUI() {
        JFrame frame = new JFrame("Layout Example");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        JPanel contentPane = new JPanel(
                        new GridLayout(0, 1, hGap, vGap));
        contentPane.setBorder(
            BorderFactory.createEmptyBorder(hGap, vGap, hGap, vGap));
        borderPanel = new JPanel(new BorderLayout(hGap, vGap));
        borderPanel.setBorder(
            BorderFactory.createTitledBorder("BorderLayout"));
        borderPanel.setOpaque(true);
        borderPanel.setBackground(Color.WHITE);
        for (int i = 0; i < 5; i++) {
            buttons[i] = new JButton(borderConstraints[i]);
            borderPanel.add(buttons[i], borderConstraints[i]);
        }
        contentPane.add(borderPanel);

        flowPanel = new JPanel(new FlowLayout(
                    FlowLayout.CENTER, hGap, vGap));
        flowPanel.setBorder(
            BorderFactory.createTitledBorder("FlowLayout"));
        flowPanel.setOpaque(true);
        flowPanel.setBackground(Color.WHITE);
        for (int i = 5; i < 8; i++) {
            buttons[i] = new JButton(Integer.toString(i));
            flowPanel.add(buttons[i]);
        }
        contentPane.add(flowPanel);

        gridPanel = new JPanel(new GridLayout(2, 2, hGap, vGap));
        gridPanel.setBorder(
            BorderFactory.createTitledBorder("GridLayout"));
        gridPanel.setOpaque(true);
        gridPanel.setBackground(Color.WHITE);
        for (int i = 8; i < 12; i++) {
            buttons[i] = new JButton(Integer.toString(i));
            gridPanel.add(buttons[i]);
        }
        contentPane.add(gridPanel);

        gridBagPanel = new JPanel(new GridBagLayout());
        gridBagPanel.setBorder(
            BorderFactory.createTitledBorder("GridBagLayout"));
        gridBagPanel.setOpaque(true);
        gridBagPanel.setBackground(Color.WHITE);
        buttons[12] = new JButton(Integer.toString(12));
        addComp(gridBagPanel, buttons[12], 0, 0, 1, 1
                            , GridBagConstraints.BOTH, 0.33, 0.5);
        buttons[13] = new JButton(Integer.toString(13));
        addComp(gridBagPanel, buttons[13], 1, 0, 1, 1
                            , GridBagConstraints.BOTH, 0.33, 0.5);
        buttons[14] = new JButton(Integer.toString(14));
        addComp(gridBagPanel, buttons[14], 0, 1, 2, 1
                            , GridBagConstraints.BOTH, 0.66, 0.5);
        buttons[15] = new JButton(Integer.toString(15));
        addComp(gridBagPanel, buttons[15], 2, 0, 1, 2
                            , GridBagConstraints.BOTH, 0.33, 1.0);
        contentPane.add(gridBagPanel);

        cardPanel = new JPanel(new CardLayout(hGap, vGap));
        cardPanel.setBorder(
            BorderFactory.createTitledBorder("CardLayout"));
        cardPanel.setOpaque(true);
        cardPanel.setBackground(Color.WHITE);
        cardPanel.add(getPanel(Color.BLUE));
        cardPanel.add(getPanel(Color.GREEN));
        contentPane.add(cardPanel);

        frame.setContentPane(contentPane);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private JPanel getPanel(Color bColor) {
        JPanel panel = new JPanel(new FlowLayout(
                    FlowLayout.CENTER, hGap, vGap));
        panel.setOpaque(true);
        panel.setBackground(bColor.darker().darker());
        JButton swapperButton = new JButton("Next");
        swapperButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent ae) {
                CardLayout cardLayout = (CardLayout) cardPanel.getLayout();
                cardLayout.next(cardPanel);
            }
        });

        panel.add(swapperButton);

        return panel;
    }

    private void addComp(JPanel panel, JComponent comp
                                , int x, int y, int gWidth
                                    , int gHeight, int fill
                                        , double weightx, double weighty) {
        gbc.gridx = x;
        gbc.gridy = y;
        gbc.gridwidth = gWidth;
        gbc.gridheight = gHeight;
        gbc.fill = fill;
        gbc.weightx = weightx;
        gbc.weighty = weighty;      

        panel.add(comp, gbc);
    }

    public static void main(String[] args) {
        Runnable runnable = new Runnable(){
            @Override
            public void run() {
                new LayoutExample().displayGUI();
            }
        };
        EventQueue.invokeLater(runnable);
    }
}

OUTPUT :