-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
NSSet *allTouches = [event allTouches]; //返回与当前接收者有关的所有的触摸对象
UITouch *touch = [allTouches anyObject]; //视图中的所有对象
CGPoint point = [touch locationInView:[touch view]]; //返回触摸点在视图中的当前坐标
int x = point.x;
int y = point.y;
if(y<self.frame.size.height - 500)
{
[self removeFromSuperview];
}
}