在 Java GUI 中如何有效使用布局管理器

在Java GUI中，布局管理器是用于自动排列组件以适应不同屏幕尺寸和分辨率的关键工具

1. 使用BorderLayout：BorderLayout将容器分为五个区域：北、南、东、西和中。将组件添加到相应的区域，以便在窗口大小改变时它们能够正确调整位置。

import javax.swing.*;

public class BorderLayoutExample {
    public static void main(String[] args) {
        JFrame frame = new JFrame("BorderLayout Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 400);

        JPanel panel = new JPanel(new BorderLayout());

        JButton northButton = new JButton("North");
        JButton southButton = new JButton("South");
        JButton eastButton = new JButton("East");
        JButton westButton = new JButton("West");
        JButton centerButton = new JButton("Center");

        panel.add(northButton, BorderLayout.NORTH);
        panel.add(southButton, BorderLayout.SOUTH);
        panel.add(eastButton, BorderLayout.EAST);
        panel.add(westButton, BorderLayout.WEST);
        panel.add(centerButton, BorderLayout.CENTER);

        frame.add(panel);
        frame.setVisible(true);
    }
}

2. 使用FlowLayout：FlowLayout按照组件添加的顺序从左到右排列它们。当一行填满时，下一个组件将移到下一行。可以通过设置组件之间的间距和垂直对齐方式来自定义布局。

import javax.swing.*;

public class FlowLayoutExample {
    public static void main(String[] args) {
        JFrame frame = new JFrame("FlowLayout Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 400);

        JPanel panel = new JPanel(new FlowLayout());

        JButton button1 = new JButton("Button 1");
        JButton button2 = new JButton("Button 2");
        JButton button3 = new JButton("Button 3");
        JButton button4 = new JButton("Button 4");
        JButton button5 = new JButton("Button 5");

        panel.add(button1);
        panel.add(button2);
        panel.add(button3);
        panel.add(button4);
        panel.add(button5);

        frame.add(panel);
        frame.setVisible(true);
    }
}

3. 使用GridLayout：GridLayout将容器分为指定行数和列数的网格。每个组件占据一个单元格，并且它们在网格中均匀分布。

import javax.swing.*;

public class GridLayoutExample {
    public static void main(String[] args) {
        JFrame frame = new JFrame("GridLayout Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 400);

        JPanel panel = new JPanel(new GridLayout(3, 3));

        for (int i = 1; i <= 9; i++) {
            JButton button = new JButton("Button " + i);
            panel.add(button);
        }

        frame.add(panel);
        frame.setVisible(true);
    }
}

4. 使用BoxLayout：BoxLayout沿着一条直线排列组件，可以水平或垂直方向。可以通过设置组件之间的间距和垂直对齐方式来自定义布局。

import javax.swing.*;

public class BoxLayoutExample {
    public static void main(String[] args) {
        JFrame frame = new JFrame("BoxLayout Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 400);

        JPanel panel = new JPanel();
        panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));

        JButton button1 = new JButton("Button 1");
        JButton button2 = new JButton("Button 2");
        JButton button3 = new JButton("Button 3");

        panel.add(button1);
        panel.add(button2);
        panel.add(button3);

        frame.add(panel);
        frame.setVisible(true);
    }
}

5. 使用GridBagLayout：GridBagLayout是一种灵活的布局管理器，允许组件跨越多个行和列。它还允许您自定义组件在其显示区域内的对齐方式和填充方式。

import javax.swing.*;

public class GridBagLayoutExample {
    public static void main(String[] args) {
        JFrame frame = new JFrame("GridBagLayout Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 400);

        JPanel panel = new JPanel(new GridBagLayout());
        GridBagConstraints GridBagConstraints = new GridBagConstraints();

        JButton button1 = new JButton("Button 1");
        GridBagConstraints.gridx = 0;
        GridBagConstraints.gridy = 0;
        panel.add(button1, GridBagConstraints);

        JButton button2 = new JButton("Button 2");
        GridBagConstraints.gridx = 1;
        GridBagConstraints.gridy = 0;
        panel.add(button2, GridBagConstraints);

        JButton button3 = new JButton("Button 3");
        GridBagConstraints.gridx = 0;
        GridBagConstraints.gridy = 1;
        GridBagConstraints.gridwidth = 2;
        panel.add(button3, GridBagConstraints);

        frame.add(panel);
        frame.setVisible(true);
    }
}

了解这些布局管理器及其使用方法后，您可以根据实际应用程序的需求选择合适的布局管理器来创建Java GUI界面。