How to find out which other UIScrollView interferes with scrollsToTop?

Question

I have several view controllers with one or multiple scrollviews. Although I have explicitly set the scrollsToTop flags in view controllers with more than one scroll view, some scroll views refuse to scroll up when I tap the status bar.

After pushing another view controller and popping it the gesture sometimes works in the view it previously hasn't.

It's very confusing and I just don't know what the problem is. How can this issue effectively be debugged? Is there a global (private) notification for the status bar tap so I could scroll the views manually?

Answer 1

I have used code like the following to debug this scenario, before:

- (void)findMisbehavingScrollViews
{
    UIView *view = [[UIApplication sharedApplication] keyWindow];
    [self findMisbehavingScrollViewsIn:view];
}

- (void)findMisbehavingScrollViewsIn:(UIView *)view
{
    if ([view isKindOfClass:[UIScrollView class]])
    {
        NSLog(@"Found UIScrollView: %@", view);
        if ([(UIScrollView *)view scrollsToTop])
        {
            NSLog(@"scrollsToTop = YES!");
        }
    }
    for (UIView *subview in [view subviews])
    {
        [self findMisbehavingScrollViewsIn:subview];
    }
}

Depending on how many UIScrollViews you find, you can modify that code to help debug your particular situation.

Some ideas:

• Change the background colors of the various scrollviews to identify them on screen.
• Print the view hierarchy of those scrollviews to identify all of their superviews.

Ideally, you should only find a single UIScrollView in the window hierarchy that has scrollsToTop set to YES.