判断手指（手势）离开屏幕 iOS、轮播图

UIScrollView轮播图，当手指放上去的时候停止播放，手指离开时开始播放。
我的实现思路是在scrollView上加一个长按手势UILongPressGestureRecognizer。

//添加长按手势
UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc]initWithTarget:self action:@selector(longUiscrollView:)];
        longPress.delegate = self;
        [_scrollV addGestureRecognizer:longPress];

//手势方法实现
- (void)longUiscrollView:(UITapGestureRecognizer *)tap{
    [self.timer invalidate];//循环终止
    self.timer = nil;
    //(手势完成时)手指离开时
    if (tap.state == UIGestureRecognizerStateEnded) {
        self.timer = [NSTimer scheduledTimerWithTimeInterval:3 target:self selector:@selector(nextPage) userInfo:nil repeats:YES];
    }
}

轮播图整个需求实现

#pragma mark - UIScrollViewDelegate

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
    NSInteger index = (self.scrollV.contentOffset.x ) / MAINSCREEN_WIDTH;
//这儿数值根据自己的需求设定
    if (index < 1) {
        self.scrollV.contentOffset = CGPointMake(2 * MAINSCREEN_WIDTH, 0);
    }else if(index > 2){
        self.scrollV.contentOffset = CGPointMake( MAINSCREEN_WIDTH, 0);
    }
}
- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView{
    [self scrollViewDidEndDecelerating:self.scrollV];
}
//开始手动滑动时停止自动播放
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{
    [self.timer invalidate];//循环终止
    self.timer = nil;
}
//结束手动滑动是开始自动播放
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{
    self.timer = [NSTimer scheduledTimerWithTimeInterval:3 target:self selector:@selector(nextPage) userInfo:nil repeats:YES];
}
- (void)nextPage{
    [self.scrollV setContentOffset:CGPointMake(self.scrollV.contentOffset.x + MAINSCREEN_WIDTH,0 )animated:YES];
}
- (void)longUiscrollView:(UITapGestureRecognizer *)tap{
    [self.timer invalidate];//循环终止
    self.timer = nil;
    //(手势完成时)手指离开时
    if (tap.state == UIGestureRecognizerStateEnded) {
        self.timer = [NSTimer scheduledTimerWithTimeInterval:3 target:self selector:@selector(nextPage) userInfo:nil repeats:YES];
    }
}