Java如何在布局中添加图像作为背景

Question

我有一个使用CardLayout的类,它有两张卡片,上面有一个按钮.我希望能够做的是放置一个像背景一样的图像,例如Windows中的桌面背景.该程序最终将有几张不同的卡片,我希望能够在每张卡片上放置不同的背景.我已尝试过在本网站上提出的其他类似问题中提出的许多建议,以及通过Google搜索我能找到的任何建议,但我似乎无法让它发挥作用.我知道使用CardLayout我不能将面板放在面板上,因此将图像放在JPanel上是行不通的.所以我的问题是,根据下面发布的代码,我有更好的方法来设置我的布局,以便它更好地工作,而且,我应该如何处理显示图像,使其在按钮的背景中？任何帮助将不胜感激.

import java.awt.*;
import java.awt.event.*;
import java.io.File;
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 {
    backgroundImage = ImageIO.read(new File("background.jpg"));

    //create cards
    JPanel card1 = new JPanel()
    {
        @Override
        public void paintComponent(Graphics g)
        {
            g.drawImage(backgroundImage, 0, 0, null);
        }
    };
    JPanel card2 = new JPanel();
    button1 = new JButton("Button 1");
    button2 = new JButton("Button 2");
    button1.addActionListener(this);
    button2.addActionListener(this);        
    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.setSize(800, 600);
    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

您需要覆盖的方法paintComponent(Graphics g)中的JPanel和使用drawImage()上的图形对象g在这个例子.

另外,请通过@trashgod检查这两个示例:

1. 例子.
2. 例子.

Answer 2

@ Eng.Fouad的答案很好,但图像可能在布局中占主导地位.您可能想要覆盖getPreferredSize(),如下所示.然后你可以只是pack()窗口,大小将是正确的.另请参阅使用getResource加载图像.

import java.awt.*;
import java.awt.event.*;
import java.io.File;
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) {
        try {
            backgroundImage = ImageIO.read(new File("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();
        button1 = new JButton("Button 1");
        button2 = new JButton("Button 2");
        button1.addActionListener(this);
        button2.addActionListener(this);
        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() {
        //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.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) {
        //schedule job for the event dispatch thread creating and showing GUI        
        EventQueue.invokeLater(new Runnable() {

            public void run() {
                    createAndShowGUI();
            }
        });
    }
}