Two UIScrollViews, synchronous scrolling

Question

I heve two UIScrollViews, they are on top of each other.

                                        UIView
                                           |
                              --------------------------
                              |                        |
                         UIScrollView1            UIScrollView2

I would like it, to work in the following way. If I scroll UIScrollView2, UIScrollView1 should also scroll by the same contentOffset. It must by done synchronously, so using scrollViewDidScroll is not an option. Do you guys have some idea, how can it be done?

Source Code

    _prContentGridView = [[PRContentGridView alloc] initWithFrame:frame];
    _prContentGridView.minimumZoomScale = 0.25;
    _prContentGridView.maximumZoomScale = 2.0;
    _prContentGridView.delegate = self;

    _prBackgroundGridView = [[PRBackgroundGridView alloc] initWithFrame:frame];

    [self addSubview:_prBackgroundGridView];
    [self addSubview:_prContentGridView];

Delegate Method

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    if (_prContentGridView.scrollEnabled == YES) {
        CGPoint p = CGPointMake(scrollView.contentOffset.x -   _prevousContentOffsetOfContentScrollView.x, scrollView.contentOffset.y - _prevousContentOffsetOfContentScrollView.y);
        [_prBackgroundGridView setContentOffset:p animated:YES];
    }
}

Answer 1

use the UIScrollViewDelegate Protocol method:

- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
  if (scrollView == UIScrollView1){
    UIScrollView2.contentOffset = scrollView.contentOffset;
  }else{
    UIScrollView1.contentOffset = scrollView.contentOffset;
  }
}

Answer 2

You should try this Code, first Declare IBOutlet in .h File,

IBOutlet UIScrollView *FirstScrollView;
IBOutlet UIScrollView *SecondScrollView;

then try this code,

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
  if ([scrollView isEqual: FirstScrollView])
  {
            SecondScrollView.contentOffset =
              CGPointMake(FirstScrollView.contentOffset.x, 0);
  }
  else
  {
            FirstScrollView.contentOffset = 
              CGPointMake(SecondScrollView.contentOffset.x, 0);
  }
}