先简单说一下需求，有一个view 需要给它添加一个拖拽手势，而且拖拽的时候不能超过屏幕边缘。看到这样一个需求，当然实现的方式有挺多的，你可以通过限制中心点的x值和y值 也可以限制view的最大x和最大y以及最小x最小y，这些都可以，今天要说的是通过限制中心点来做，有需要的可以自己拿去用：
//添加手势
UIView * cyanView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 60, 60)];
cyanView.backgroundColor = [UIColor cyanColor];
[self.view addSubview:cyanView];
UIPanGestureRecognizer * panGestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self
action:@selector(panGes:)];
[cyanView addGestureRecognizer:panGestureRecognizer];
-(void)panGes:(UIPanGestureRecognizer *)recognizer{
CGPoint translation = [recognizer translationInView:self.view];
CGPoint newCenter = CGPointMake(recognizer.view.center.x+ translation.x,
recognizer.view.center.y + translation.y);
// 限制屏幕范围：
newCenter.y = MAX(recognizer.view.frame.size.height/2, newCenter.y);
newCenter.y = MIN(self.view.frame.size.height - recognizer.view.frame.size.height/2, newCenter.y);
newCenter.x = MAX(recognizer.view.frame.size.width/2, newCenter.x);
newCenter.x = MIN(self.view.frame.size.width - recognizer.view.frame.size.width/2,newCenter.x);
recognizer.view.center = newCenter;
[recognizer setTranslation:CGPointZero inView:self.view];
}
搞定，收工，希望能帮到有需要的小伙伴
