UIScrollView添加手势解决冲突

UIScrollView默认手势有：PagingSwipeGestureRecognizer、DelayedTouchesBeganGestureRecognizer、PanGestureRecognizer；UITableview只有后两个手势；

一般在含有UIScrollView或者UIScrollView的子类的视图上添加自己的手势就会有冲突；利用UIGestureRecognizerDelegate中的代理方法可以解决相应的冲突；

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch

该代理方法可以拦截相应的手势，返回YES为拦截手势；返回NO为不做处理；
相应的手势被拦截之后，就会执行另一个代理方法：

- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer

例如：

场景：实现一个父子控制器，然后再划到最两边的时候，实现抽屉效果；
实现：在主控制器的view上添加pan 手势，不做任何处理时，系统默认执行UIScrollView的手势；在第一个代理方法中判断UIScrollView的偏移量，然后拦截手势；然后在第二个代理方法对其进行相应的处理；

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch{
    if ([gestureRecognizer isKindOfClass:[UIPanGestureRecognizer class]]) {
        CGFloat offsetX = self.scrollView.contentOffset.x;
       //满足条件拦截手势
        if (offsetX == self.scrollView.contentSize.width - screenSize.width || offsetX == 0.0) {
                return YES;
        }
    }
    return NO;
}

- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer{
    if ([gestureRecognizer isKindOfClass:[UIPanGestureRecognizer class]]) {
        UIPanGestureRecognizer *pan = (UIPanGestureRecognizer *)gestureRecognizer;
        CGPoint translation = [pan translationInView:self.view];
        CGFloat offsetX = self.scrollView.contentOffset.x;
        if (translation.x > 0 && offsetX == 0.0 ) {
                if ([self.delegate respondsToSelector:@selector(centerControllerPrepareLeftView:)]) {
                    [self.delegate centerControllerPrepareLeftView:self];
                }
        }else if (translation.x < 0 && offsetX == self.scrollView.contentSize.width - screenSize.width){
                if ([self.delegate respondsToSelector:@selector(centerControllerPrepareRightView:)]) {
                    [self.delegate centerControllerPrepareRightView:self];
                }
        }
    }
    return YES;
}