Syncing another animation with interactivePopGestureRecognizer interactive transition

Question

I have this custom back button in the bottom left corner of my app. The button transitions out downwards when there is no more view controllers on the navigation stack then just the root one. Now i introduced the "swipe to pop" functionality that is standard with iOS7 and i would like to make the button transition based on how far the swipe gesture has moved the view it's popping.

I have gotten so far as to add a my own navigation controller as a target to the the interactivePopGestureRecognizer to receive the the swipe actions. So I know when the swipe starts, moves (velocity, direction and point) and when it stops. So i could make the position of the back button dependent on where the finger are on the screen without a problem.

The problem is that when the user lifts her fingers from the screen the view either pops or return to its original position. The only way i found to detect this is in the UINavigationControllerDelegate method - (void)navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated this method is called when the view that the app is returning to is fully visible (the animation has finished popping). So the way to know if the view did not pop is to wait some time after touches ended and se if the above method is called, this is of course not a good solution.

The absolute best situation would be if i could get notified about the position of the animation and the completion/reversal of the animation. Another thing to mention is that approximating will be hard i think since the decision to pop or not is not only made by the screen location of the finger upon release but also velocity etc.

Any tips would be greatly appreciated.

Answer 1

I did manage to solve this kind of anyway. Managing to at least get notified if animation completes or not. I posted my answer in another question similar to this, here hope it helps.