MDCDialogTransitionController.m

/*
 Copyright 2016-present the Material Components for iOS authors. All Rights Reserved.

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

 http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */

#import "MDCDialogTransitionController.h"

#import "MDCDialogPresentationController.h"

@implementation MDCDialogTransitionController

static const NSTimeInterval MDCDialogTransitionDuration = 0.27;

#pragma mark - UIViewControllerAnimatedTransitioning

- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext {
  return MDCDialogTransitionDuration;
}

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext {
  // If a view in the transitionContext is nil, it likely hasn't been loaded by its ViewController
  // yet.  Ask for it directly to initiate a loadView on the ViewController.
  UIViewController *fromViewController =
      [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
  UIView *fromView = [transitionContext viewForKey:UITransitionContextFromViewKey];
  if (fromView == nil) {
    fromView = fromViewController.view;
  }

  UIViewController *toViewController =
      [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
  UIView *toView = [transitionContext viewForKey:UITransitionContextToViewKey];
  if (toView == nil) {
    toView = toViewController.view;
  }

  UIViewController *toPresentingViewController = toViewController.presentingViewController;
  BOOL presenting = (toPresentingViewController == fromViewController) ? YES : NO;

  UIViewController *animatingViewController = presenting ? toViewController : fromViewController;
  UIView *animatingView = presenting ? toView : fromView;

  UIView *containerView = transitionContext.containerView;

  if (presenting) {
    [containerView addSubview:toView];
  }

  CGFloat startingAlpha = presenting ? 0.0f : 1.0f;
  CGFloat endingAlpha = presenting ? 1.0f : 0.0f;

  animatingView.frame = [transitionContext finalFrameForViewController:animatingViewController];
  animatingView.alpha = startingAlpha;

  NSTimeInterval transitionDuration = [self transitionDuration:transitionContext];
  UIViewAnimationOptions options =
      UIViewAnimationOptionAllowUserInteraction | UIViewAnimationOptionBeginFromCurrentState;

  [UIView animateWithDuration:transitionDuration
      delay:0.0
      options:options
      animations:^{
        animatingView.alpha = endingAlpha;
      }
      completion:^(BOOL finished) {
        // If we're dismissing, remove the presented view from the hierarchy
        if (!presenting) {
          [fromView removeFromSuperview];
        }

        // From ADC : UIViewControllerContextTransitioning
        // When you do create transition animations, always call the
        // completeTransition: from an appropriate completion block to let UIKit know
        // when all of your animations have finished.
        [transitionContext completeTransition:YES];
      }];
}

#pragma mark - UIViewControllerTransitioningDelegate

- (UIPresentationController *)
    presentationControllerForPresentedViewController:(UIViewController *)presented
                            presentingViewController:(UIViewController *)presenting
                                sourceViewController:(UIViewController *)source {
  return [[MDCDialogPresentationController alloc] initWithPresentedViewController:presented
                                                         presentingViewController:presenting];
}

- (id<UIViewControllerAnimatedTransitioning>)
    animationControllerForPresentedController:(UIViewController *)presented
                         presentingController:(UIViewController *)presenting
                             sourceController:(UIViewController *)source {
  return self;
}

- (id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:
        (UIViewController *)dismissed {
  return self;
}

@end