This video shows the issue I am having. http://www.youtube.com/watch?v=C9od_2KZAbs
I am attempting to create a custom interactive push transition using a UIPanGestureRecognizer. I have an interactive transition delegate (using UIPercentDrivenInteractiveTransition) and a transition animator. completeTransition: seems to re-animate the push unnecessarily.
Here is how the pan gesture controls the transition:
- (void) panGestureRecognized:(UIPanGestureRecognizer *) gestureRecogznier {
CGPoint translation = [gestureRecogznier translationInView:gestureRecogznier.view];
if (gestureRecogznier.state == UIGestureRecognizerStateBegan) {
self.interactiveTransitionAnimator = [[UIPercentDrivenInteractiveTransition alloc] init];
EVDetailViewController *detailViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"EVDetailViewController"];
[self.navigationController pushViewController:detailViewController animated:YES];
}
else if (gestureRecogznier.state == UIGestureRecognizerStateChanged) {
CGFloat d = (translation.x / CGRectGetWidth(self.view.bounds)) * -1;
[self.interactiveTransitionAnimator updateInteractiveTransition:d];
}
else if (gestureRecogznier.state == UIGestureRecognizerStateEnded) {
if ([gestureRecogznier velocityInView:self.view].x < 0) {
[self.interactiveTransitionAnimator finishInteractiveTransition];
} else {
[self.interactiveTransitionAnimator cancelInteractiveTransition];
}
self.interactiveTransitionAnimator = nil;
}
}
The UINavigationControllerDelegate handles the vending of both transition delegate objects, which is triggered when pushViewController: is called.
The transition animator has a very simple animation:
- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext {
UIViewController* toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
[[transitionContext containerView] addSubview:toViewController.view];
CGRect finalToVCFrame = [transitionContext finalFrameForViewController:toViewController];
if (self.operation == UINavigationControllerOperationPush) {
// set offscreen to the right
toViewController.view.frame = CGRectMake(320.0f, 0.0f, 320.0f, 568.0f);
[UIView animateWithDuration:[self transitionDuration:transitionContext] delay:0.0f options:0 animations:^{
toViewController.view.frame = finalToVCFrame;
} completion:^(BOOL finished) {
// *** When this is called, the glitch occurs
[transitionContext completeTransition:YES];
}];
}
}
In the video, the pan gesture ends about 60% of the way through, which triggers the finishInteractiveTransition call. Everything goes smoothly until the completion block in the UIView block-based animation calls completeTransition:. When this method is called, the toViewController re-animates the last part of the push animation unnecessarily. In the video the red view is the window. The animation duration is 3 seconds.
I cannot figure out why this happens. It looks like the animation between the point when the gesture ends and when completeTransition: is called happens twice. Any ideas?
Found a workaround that works.
added
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
[transitionContext completeTransition:![transitionContext transitionWasCancelled]];
});
Within your completion handler.
works for me.
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