窗口背景图片插入

		// 创建主窗口
		JFrame frame = new JFrame("xxxxx");

		frame.setSize(1200, 700);
		frame.setLocation(350, 200);
		JLabel label = new JLabel();

        //新建一个类
    import java.awt.Graphics;
    import java.awt.Image;
 
    import javax.swing.ImageIcon;
    import javax.swing.JPanel;
 
    public class PictureJPanel extends JPanel{
         
        private ImageIcon icon;
        private Image image;
     
        public PictureJPanel() {
            icon = new ImageIcon(getClass().getResource("/bg.jpg"));
            image = icon.getImage();
        }
        public void paintComponent(Graphics g) {  
            super.paintComponent(g);  
            //下面这行是为了背景图片可以跟随窗口自行调整大小，可以自己设置成固定大小  
        g.drawImage(image, 0, 0,this.getWidth(), this.getHeight(), this);  
         }  
    }

        //主类里 背景图片插入
		PictureJPanel pj = new PictureJPanel();
		pj.repaint();
		pj.setSize(1200, 675);
		pj.setLocation(0, 0);
		frame.repaint();
		frame.add(pj);