使用内部类为JPanel添加背景图片

效果图：

DEMO：

package test;

import java.awt.Graphics;
import java.awt.Image;

import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class BGJFrame{

    private JPanel contentPane;
    private JFrame frame;
    private Image image = new ImageIcon("C:\\Users\\Administrator\\Pictures\\coffee.jpg").getImage();  
    public static void main(String[] args) {
        new BGJFrame();
    }

    public BGJFrame() {
        frame = new JFrame();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setBounds(100, 100, 450, 300);
        contentPane = new JPanel(){
              protected void paintComponent(Graphics g) { 
                  g.drawImage(image, 0, 0, this.getWidth(), this.getHeight(), this);  
              }  
        };
        frame.setContentPane(contentPane);          
        contentPane.setLayout(null);
    }
}