Adjusting position together with interactivePopGestureRecognizer - iphone

Question

I have a custom control, containing a row of buttons, that mimics the tab bar. This control slides out of view when the UINavigationController navigates away from the root view controller, and slides back in when navigating to the root.
With iOS 7, there is the UIScreenEdgePanGestureRecognizer that gives the swipe-to-go-back gesture. I am thus modifying my custom control so that the slide amount corresponds to the UIScreenEdgePanGestureRecognizer's translation.
Problem is, when the user releases the touch, how do I tell if the UINavigationController will navigate back or bounce back to the original view?
[self.interactivePopGestureRecognizer addTarget:self action:#selector(panningBack:)];
- (void) panningBack:(UIPanGestureRecognizer *)recognizer
{
// Snipped - Code that reads the recognizer translation and adjust custom control y position
if (recognizer.state == UIGestureRecognizerStateEnded)
{
// Question: Does it go back, or does it not?
// If it goes back, slide custom control into view
// Else slide custom control out of view
}
}

Answer 1

I know this is a rather old question so the answer might not be of use to the OP but maybe to some one else. I faced the same problem yesterday and did a lot of searching on SO an the rest of the web without really finding anything.
So here is the solution I used for a similar problem. This is implemented in the navigationcontroller delegate but i guess you can do it some other place if that fits your need better.
- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated
{
id<UIViewControllerTransitionCoordinator> tc = navigationController.topViewController.transitionCoordinator;
[tc notifyWhenInteractionEndsUsingBlock:^(id<UIViewControllerTransitionCoordinatorContext> context) {
NSLog(#"DONE!!!");
NSLog(#"Container View: %#", [context containerView]);
NSLog(#"From VC: %#", [context viewControllerForKey:UITransitionContextFromViewControllerKey]);
NSLog(#"To VC: %#", [context viewControllerForKey:UITransitionContextToViewControllerKey]);
NSLog(#"Initially Interactive: %i", [context initiallyInteractive]);
NSLog(#"Completion Curve: %d", [context completionCurve]);
NSLog(#"Is Animated: %i", [context isAnimated]);
NSLog(#"Is Cancelled: %i", [context isCancelled]);
NSLog(#"Is Interactive: %i", [context isInteractive]);
NSLog(#"Percent Complete: %f", [context percentComplete]);
NSLog(#"Presentation Style: %d", [context presentationStyle]);
NSLog(#"Transition Duration: %f", [context transitionDuration]);
}];
}
This will fire when user lift her finger and the animation is rather reversed or completed. The [context isCancelled]; will tell you if it reversed or completer. And there is also a lot of other nice info in the context object that can be to use.

Answer 2

I would say the easiest solution is to use the default gesture implemented in the navigation controller. When the view appears show the bar and hide the bar when it disappears.
An elegant solution for knowing if it should go back or not, would be to detect the last movement.
Meaning if the user went some pixels to the left and releases -> bounce back
if the user went some pixels to the right and releases -> show previous controller
This can be done if you save the location in state changed and compare it to state ended.
Getting the point like this:
CGPoint point = [recognizer locationInView:view];