在scrollView上增加滑动手势（Pan）

view上有一个scrollView，现在想在view上加一个Pan手势，需求是：当向下划的时候，整个view动，但是scrollView不动；其它情况下scrollView动而view不动。

解决方法：

-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
  return YES;
}

// 给加的手势设置代理, 并实现此协议方法
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer {
  if ([gestureRecognizer isKindOfClass:[UIPanGestureRecognizer class]]) {
    
    UIPanGestureRecognizer *pan = (UIPanGestureRecognizer *)gestureRecognizer;
    CGPoint pos = [pan velocityInView:pan.view];
    if (pos.y > 0) {
      self.contentScrollView.scrollEnabled = NO;
      return YES;
    }
  }
  
  return NO;
}