根据滑动的手势动态显示隐藏系统导航栏、状态栏，超灵敏

关键代码如下：

@property (nonatomic, assign)CGFloat  lastPosition;

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    if (self.collectionView==scrollView&&_disappear==NO) {
        
        CGFloat currentPostion = scrollView.contentOffset.y;
        
        CGRect bounds       = scrollView.bounds;
        CGSize size         = scrollView.contentSize;
        UIEdgeInsets inset  = scrollView.contentInset;
        CGFloat currentBottomOffset     = currentPostion + bounds.size.height - inset.bottom;
        CGFloat maxBottomOffset         = size.height;
        CGFloat minBottomOffset         = -64 + bounds.size.height - inset.bottom;
        
        //非上拉刷新、底部刷新状态
        if (minBottomOffset < currentBottomOffset && currentBottomOffset<=maxBottomOffset) {
            
            if (currentPostion - _lastPosition > 0 ) {
                
                NSLog(@"向上滚动 隐藏导航栏");
                [[UIApplication sharedApplication] setStatusBarHidden:YES withAnimation:UIStatusBarAnimationFade];
                [self.navigationController setNavigationBarHidden:YES animated:YES];
                
            }else if ( currentPostion - _lastPosition < 0 ){
                
                NSLog(@"向下滚动 显示导航栏");
                [[UIApplication sharedApplication] setStatusBarHidden:NO withAnimation:UIStatusBarAnimationFade];
                [self.navigationController setNavigationBarHidden:NO animated:YES];
            }
            
            _lastPosition=currentPostion;
        }
    }
}