......
public void paint(Graphics g){
    int i;
    g.setColor(Color.green);
    for(i=0;i<3;i++){
        g.fillOval(xspots[i]-2,yspots[i]-2,4,4);
}
    if(currspots==3){
    setBackground(Color.red);
    g.setColor(Color.black);
    for(i=0;i<3;i++){
        g.drawLine(xspots[i-1],yspots[i-1],xspots[i],yspots[i]);
}
        g.drawLine(xspots[i-1],yspots[i-1],xspots[0],yspots

}

  上面是在做接鼠标的按键问题,当鼠标选中三个位置是,背景也会变色,但是就是不画线,请问是怎么回事?