int i; //记录重绘次数
          public void display(Shape shape,Ground ground){
        System.out.println("GamePanel's display begin");
        this.shape = shape;
        this.ground = ground;
        repaint();
        System.out.println("GamePanel's display  end");
    }
    @Override
    protected void paintComponent(Graphics g) {
        // TODO Auto-generated method stub
        
        if(shape !=null && ground != null){
            
            System.out.println(i++);
            shape.drawMe(); //此方法会打印Shape's drawMe
            ground.drawMe(); //此方法会打印Ground's drawMe
        }
    }

        public void componentShown(ComponentEvent e) {
            if (shouldShow()) {
                synchronized (getTreeLock()) {
                    if (peer != null) {
                        peer.show();
                    }
                }
            }
        }

------解决方案--------------------
只要窗体显示、布局、位置稍有改变都会触发...