Question

java通过鼠标事件绘制图形，绘制第二个时怎么让之前的不消失

java通过鼠标事件绘制图形，绘制第二个时用什么方法让之前绘的图形依然保持在面板上？
class PanelM extends JPanel
{
ImageIcon icon = new ImageIcon("app.gif");
JLabel jl = new JLabel(icon,SwingConstants.CENTER);
int x,y;
boolean boo = false;
public PanelM()
{
add(jl);
addMouseListener(new MouseAdapter()
{
public void mousePressed(MouseEvent m)
{
int mods = m.getModifiers();
if((mods & InputEvent.BUTTON1_MASK) != 0)
{
x = m.getX();
y = m.getY();
repaint();
boo = true;
}
}
});

}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
if(boo)
g.fillOval(x, y, 20, 20);
}
}

Answer 1

public void paintComponent(Graphics g)
{

if(boo)
g.fillOval(x, y, 20, 20);
}
paintComponent方法默认清屏，试着去掉super.paintComponent(g);