iPhone: How to Tell Which Scrollview Calls the Delegate Methods?

Question

The answer to this is probably right under my nose, but I am not seeing it. Maybe someone here could help.

I have a scrollView that allows for vertical scrolling. I set it up:

[clefScrollView addSubview:clefView];
[clefScrollView setContentSize:CGSizeMake(clefView.frame.size.width, clefView.frame.size.height)];
clefScrollView.showsVerticalScrollIndicator = YES;
clefScrollView.showsHorizontalScrollIndicator = NO;
clefScrollView.delegate = self;

I have the following methods included in the same file, in order to support the UIScrollViewDelegate protocol:

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
    NSLog(@"%f %f", scrollView.contentOffset.y, scrollView.contentSize.height);
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    NSLog(@"scrollViewDidEndDecelerating");
}

- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView
{
    NSLog(@"scrollViewDidEndScrollingAnimation");
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    NSLog(@"scrollViewDidScroll");
}

In addition, the .h file for my class includes the protocol:

@interface ClefNotesViewController : UIViewController <UIActionSheetDelegate,UIScrollViewDelegate,DoneWithVCDelegate> {

The problem is that no matter what, the following two are never called:

    -scrollViewDidEndDecelerating
    -scrollViewDidScroll

The other two methods do get called in response to different events. Given that two of the protocol methods are getting called, I assume that I have correctly set the delegate to my self. So, what is the problem?

Thanks!

Update: I found the problem, although haven't still figured out how to resolve it. My class spans two files. In the second file, a different scrollView is implementing -scrollViewDidEndDecelerating -scrollViewDidScroll

THe question is, how can I define two different sets of methods for two different UIScrollViews, in the same class?

I could try to handle two scrollViews with the same delegate methods, but that's ugly since I won't be able to keep each set of delegates with the scrollView's file. I could also split my class. Is there another way?

Answer 1

THe question is, how can I define two different sets of methods for two different UIScrollViews, in the same class?

The delegate methods accept a scrollview objects as their parameter. You need to check which scrollview is being passed and respond accordingly. You can set each scrollview's tag property in order to identify them.

Answer 2

You just need to compare the pointers with what is passed into the methods

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
    if(scrollView == self.firstScrollView){
          // do something
    }
    else if(scrollView == self.secondScrollView){
          // do something else
    }
}

This is assuming that your scrollviews are properties on the class. I'm pretty sure that a pointer comparison is fine here. If it gives you trouble use something like

if(scrollView.tag == self.firstScrollView.tag)

You will need to assign them a tag when you create them