Select current button that is showing in UIScrollView programmatically

Question

I have a UIScrollView with paging enabled. In every page I have a button. I want that with every swipe the button that is showing in the UIScrollView will be selected.

I'm guessing that the solution will be based on

-(void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate

but how can I know which button is showing without too many calculations of the range & offset?

Thanks

Answer 1

The easiest way is to set a tag for each UIButton from your UIScrollView that is equal with the pageNumber+1 (+1 because for the page 0 the tag will be 1 and all the defaults tags are 0 so you can find the button). Then you can compute the tag in viewDidEndDecelerating/viewDidScroll or other scroll view delegate methods, depending on want you need. I'm doing the all the computation in viewDidEndDecelerating something like this:

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    int page = scrollView.contentOffset.x / scrollView.frame.size.width;
    //now you have the current page so you can get the button 
    UIButton *button =(UIButton *) [scrollView viewWithTag:page+1]; //the +1 that I was talking about above
   button.selected = YES;
}

Also you may want to deselect the other buttons, so you can find them also by tags something like:

for(int i = 1; i<=numberOfPages; i++) { 
     UIButton *button =(UIButton *) [scrollView viewWithTag:i];
     button.selected = NO;
  }

But make sure you call the for loop before the part where you are enable the button.