Open Radar

 
11-Oct-2012 03:56 PM Andrew R Madsen:
Summary:

-scrollViewDidZoom: is not called, nor is -zoomScale continuously updated during a UIScrollView zoom bounce animation. This makes it impossible to properly update subview layout during a zoom bounce. In particular, for a zoomable scroll view with some semi-stationary subviews (for example a header view) that scroll in one direction but not another, and don't zoom, layout breaks, and a "fly in" animation is seen during zoom bounce.

Steps to Reproduce:

1. Create a UIScrollView with one zoomable subview, and a sibling, semi-stationary, non-zoomable subview.
2. In -[UIScrollViewSubclass layoutSubviews] and/or -[UIScrollViewDelegate scrollViewDidZoom:scrollViewDidScroll:], update the layout of the non-zoomable, semi-stationary subview.
3. Zoom in past the maximum zoom scale, then release.

Expected Results:

-layoutSubviews and -scrollViewDidZoom: are continuously called during the zoom bounce just as they are during other zoom operations, and zoomScale, contentSize, etc. are updated continuously as expected.

Actual Results:

These methods are called once with final values instead of being called continuously during the animation.

Notes:

http://stackoverflow.com/questions/3993532/in-ios-4-0-why-does-uiscrollview-zoomtorectanimated-not-trigger-the-scrollvie
http://stackoverflow.com/questions/7319906/how-to-make-uiscrollview-send-scrollviewdidscroll-messages-during-animations
http://stackoverflow.com/questions/5799153/uiscrollview-not-calling-layoutsubviews-while-zooming-on-ios-4-0?lq=1

(none of these are my questions)