运行后无法显示界面

``@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
System.out.println(this.getClass());
ImageIcon icon = new ImageIcon(this.getClass().getResource("/images/bg.png"));
g.drawImage(icon.getImage(), 0,0,this.getWidth(),this.getHeight(),this);
}
`
在这里输入代码