observe scroll view's 'dragging' property but received no notification
cocoa-touch, key-value-observing, objective-c, uiscrollview, uiscrollviewdelegate
Solution
UIKit is not KVO-compliant in general. The fact that some properties may generate change notifications isn't reliable - it's not documented and may change in future versions etc.
Since you need to reuse this reposition logic, why not separate it properly? Btw - you can place it in your custom view class itself.
Problem
I have a custom `UIView` that is added to as a `subView` of a `UIScrollView`, and I want that `UIView` automatically repositioned whenever the `UIScrollView` scrolls. In addition to observe the `UIScrollView's` `contentOffset` property(which works fine), I also need observes its `dragging` property: ``` [scrollView addObserver:self forKeyPath:@"dragging" options:NSKeyValueObservingOptionNew context:NULL]; ``` but in the `observeValueForKeyPath:ofObject:change:context` method, I didn't receive any `NSNotification` for the change of the `dragging` property, what's the problem here? Thanks. updated Since i'm gonna reuse this custom `UIView` in multiple `UIViewControllers`, I want the custom view itself handles the repositioning logic, rather than duplicate the repositioning logic in each `UIViewController's` `UIScrollViewDelegate` methods(like `scrollViewDidScroll` thing).