Java 可以使用 GridBagLayout 来组织 CardLayout 中使用的 JPanel

Question

我是布局方面的新手，我现在使用的是 CardLayout，它有两张不同的卡片，目前绘制了背景图像和一个按钮。如下所示，该按钮位于屏幕顶部，我想将其放置在靠近底部的位置。我的理解是 GridBagLayout 将是实现该目标的最佳方式。所以我的第一个问题是，这是真的吗？而且，如果我想放置 GridBagLayout 的 JPanel 是 CardLayout 中的卡片，是否可以这样做。随着我进一步深入项目，我想将许多其他对象放入 GridBagLayout(如果这是最好的方法并且可能的话)，因此非常感谢任何关于正确方向的建议。

import java.awt.*;
import java.awt.event.*;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;

public class Cards implements ActionListener {    
private JPanel cards;
private JButton button1;
private JButton button2;
private Image backgroundImage;

public void addComponentToPane(Container pane) throws IOException {
    try {           
        backgroundImage = ImageIO.read(getClass().getResource("resources/background.jpg"));         
    } catch (IOException ex) {
        ex.printStackTrace(System.err);
    }

    //create cards
    JPanel card1 = new JPanel()
    {
        @Override
        public void paintComponent(Graphics g)
        {
            super.paintComponent(g);
            g.drawImage(backgroundImage, 0, 0, null);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(
                    backgroundImage.getWidth(null),
                    backgroundImage.getHeight(null));
        }
    };
    JPanel card2 = new JPanel()
    {
        @Override
        public void paintComponent(Graphics g)
        {
            super.paintComponent(g);
            g.drawImage(backgroundImage, 0, 0, null);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(
                    backgroundImage.getWidth(null),
                    backgroundImage.getHeight(null));
        }
    };
    //create buttons
    button1 = new JButton("Button 1");
    button2 = new JButton("Button 2");
    button1.addActionListener(this);
    button2.addActionListener(this);
    //add buttons to cards
    card1.add(button1);        
    card2.add(button2);
    //create panel that contains cards
    cards = new JPanel(new CardLayout());
    cards.add(card1, "Card 1");
    cards.add(card2, "Card 2");
    pane.add(cards, BorderLayout.SOUTH);        
}

public void itemStateChanged(ItemEvent evt) {
    CardLayout cl = (CardLayout)(cards.getLayout());
    cl.show(cards, (String)evt.getItem());
}

public static void createAndShowGUI() throws IOException  {
    //create and setup window
    JFrame frame = new JFrame("Frame"); 
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        
    //create and setup content pane
    Cards main = new Cards();
    main.addComponentToPane(frame.getContentPane());        
    //display window
    frame.pack();       
    //frame.setResizable(false);
    frame.setVisible(true);
}

public void actionPerformed(ActionEvent ae) {
    if (ae.getSource() == button1) {
        CardLayout cl = (CardLayout) (cards.getLayout());
        cl.show(cards, "Card 2");     
    } else if (ae.getSource() == button2) {
        CardLayout cl = (CardLayout) (cards.getLayout());
        cl.show(cards, "Card 1");
    }        
}            

public static void main(String[] args) {
    //set look and feel
    try {
        UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
    } catch (UnsupportedLookAndFeelException ex) {
        ex.printStackTrace();
    } catch (IllegalAccessException ex) {
        ex.printStackTrace();
    } catch (InstantiationException ex) {
        ex.printStackTrace();
    } catch (ClassNotFoundException ex) {
        ex.printStackTrace();
    }                

    //schedule job for the event dispatch thread creating and showing GUI        
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
        public void run() {                   
                    try {
                        createAndShowGUI();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }                
        }
    });     
}   
}

Answer 1

一个 GridBagLayout 会做你想做的，是的。它是可用的最灵活(但也是最复杂的)LayoutManager 之一。这是否是“最佳”方法取决于您要添加到面板的其他控件，是否要调整它们的大小，父 JPanel 时您希望发生什么调整大小和其他因素。

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