UIKonf 2014 - Building Better Transition

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Building Better Transitions By eric allam

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1986

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Mimic Physical Reality in an interesting way

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Transitions are high stakes

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principles of animation + iOS transition system

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Stretch and Squash. Timing. Anticipation. Staging. Follow-through and Overlapping Action. Straight Ahead Action and Pose-to-Pose Action. Slow in and Slow out. Arcs. Exaggeration. Secondary Action. Appeal.

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Timing Arcs & Appeal Staging

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Timing

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UIViewAnimationOptionCurve*

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Timing is: The velocity speed of an action

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Not too slow or too fast

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Too fast leads to strobing

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not just animateWithDuration:

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Speed = duration / distance

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Default Transition 0.5 seconds Spring Animation usingSpringWithDamping:10 initialSpringVelocity:0 Full Screen

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Custom Modal Transition

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- (NSTimeInterval)transitionDuration: (id)transitionContext - (void)animateTransition: (id)transitionContext

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transitionDuration: Tells the transition system how long the transition should take

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animateTransition: This is where you perform the transition's animation

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UIViewControllerContextTransitioning Gives you access to both the "from" and "to" controllers, as well as the "container" view

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UIView *fromView = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey].view; UIView *toView = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey].view; UIView *container = [transitionContext containerView];

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Add toView to containerView

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Set toView's initial state

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Animate to toView's final state

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Complete Transition

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[transitionContext completeTransition:YES];

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Example

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In animateTransition: toView.bounds = CGRectMake(0, 0, 280, 180); toView.center = CGPointMake(container.center.x, -90); [container addSubview:toView];

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[UIView animateWithDuration:duration animations:^{ toView.center = container.center; } completion:^(BOOL finished) { [transitionContext completeTransition:YES]; }];

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200ms <= duration <= 500 ms

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Slow in and Slow Out

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Ease In and Ease Out

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Follow through

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Arcs

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Appeal

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Enter the 3rd Dimension

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CATransform3D

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CGAffineTransform + z axis

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transform.m34 = - 1.0 / 500.0;

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In animateTransition: UIView *container = [transitionContext containerView]; CATransform3D perspective = CATransform3DIdentity; perspective.m34 = - 1.0 / 500.0; container.layer.sublayerTransform = perspective;

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Rotate toView around x-axis toView.layer.anchorPoint = CGPointMake(0.5, 0); toView.layer.position = adjustedPosition; toView.layer.transform = CATransform3DMakeRotation(M_PI_4, 1.0, 0, 0);

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[UIView animateWithDuration:duration animations:^{ toView.layer.transform = CATransform3DIdentity; toView.layer.position = centerPosition; } completion:^(BOOL finished) { container.layer.sublayerTransform = CATransform3DIdentity; toView.layer.transform = CATransform3DIdentity; toView.layer.anchorPoint = CGPointMake(0.5, 0.5); toView.layer.position = container.center; [transitionContext completeTransition:YES]; }];

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Guidelines for 3D transitions · Reset anchor points, transform, and positions on completion · Add perspective using the container view's sublayerTransform · Spring animations generally don't look right

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Staging Present main idea clearly

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Presenting self.startingPoint = self.sharedView.center; self.startingBounds = self.sharedView.bounds; self.sharedView.center = [toView convertPoint:self.startingPoint fromView:fromView]; [toView addSubview:self.sharedView];

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Animate [UIView animateWithDuration:duration animations:^{ toView.center = container.center; self.sharedView.center = CGPointMake(140, 90); self.sharedView.bounds = CGRectMake(0, 0, 100, 100); } completion:^(BOOL finished) { [transitionContext completeTransition:YES]; }];

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Dismissal animation [UIView animateWithDuration:duration animations:^{ fromView.center = CGPointMake(container.center.x, -90); self.sharedView.center = [fromView convertPoint:self.startingPoint fromView:toView]; self.sharedView.bounds = self.startingBounds; }

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Dismissal completion completion:^(BOOL finished) { self.sharedView.center = [toView convertPoint:self.sharedView.center fromView:fromView]; [toView addSubview:self.sharedView]; [transitionContext completeTransition:YES]; }];

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1. Store off shared views center/ bounds

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2. Convert to the presented view's coordinate space and add to hierarchy

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3. Animate

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4. On dismissal, convert back to presenting view's coordinate space and hierarchy

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Bring your transitions to life

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Anticipation

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Overlapping Action

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Stretch and Squash

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Illusion of Life

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Principles of Traditional Animation applied to 3D Computer animation

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Fingers

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Animated transitions are selfish jerks

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[UIApplication beginIgnoringInteractionEvents]

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Learn this one simple trick...

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Turn animated transitions into interactive transitions

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[UIApplication beginIgnoringInteractionEvents]

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Take all the code in animateTransition:

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And put it in startInteractiveTransition:

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- (void)startInteractiveTransition: (id ) transitionContext;

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Normal interactive transition: Gesture -> Animation

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Interactive animated transition: Animation -> Gesture? - > Animation?

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UIPanGestureRecognizer *gesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(didPan:)]; [container addGestureRecognizer:gesture]; gesture.delegate = self;

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Allow interaction [UIView animateWithDuration:duration delay:0 options:UIViewAnimationOptionAllowUserInteraction animations:^{ toView.center = container.center; };

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UIViewAnimationOptionAllowUserInter action

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Use the finished param completion:^(BOOL finished) { if (finished){ [gesture.view removeGestureRecognizer:gesture]; [transitionContext finishInteractiveTransition]; [transitionContext completeTransition:YES]; } }]

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Cancel animations when pan begins CALayer *layer = toView.layer.presentationLayer; toView.center = layer.position; [toView.layer removeAllAnimations];

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Move view as pan changes CGPoint translation = [gesture translationInView:container]; CGPoint viewCenter = toView.center; viewCenter.x += translation.x; viewCenter.y += translation.y; toView.center = viewCenter; [gesture setTranslation:CGPointZero inView:[self.context containerView]];

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Finish or cancel when pan ends if (shouldFinish) { [self.context finishInteractiveTransition]; // Animate to center }else{ [self.context cancelInteractiveTransition]; // Animate off screen }

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Complete transition BOOL completed = ![self.context transitionWasCancelled]; [self.context completeTransition:completed];

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UIViewAnimateionCurveEaseInOut

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Animation as physically degrading continuations of gestures?

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Animations don't have a "starting velocity" input

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spring animation initialSpringVelocity:?

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"For smooth start to the animation, match this value to the view’s velocity as it was prior to attachment"

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initalSpringVelocity:panVelocity

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pan velocity / animation distance

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UIKit Dynamics Facebook's POP Manually

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http://www.objc.io/issue-12/interactive- animations.html

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1. Move code to startInteractiveTransition:

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2. Allow user interaction

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3. Remove animations when gesture begins

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4. Finish or cancel when gesture ends

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5. Animate to final position

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6. Complete the transition

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Navigation transitions

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Update percent complete - updateInteractiveTransition:(CGFloat)percentComplete

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Use display link

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Create right before animation starts self.startTime = CACurrentMediaTime(); self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(tick:)]; [self.displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];

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Calculate and update percent complete - (void)tick:(CADisplayLink *)link { CGFloat complete = (link.timestamp - self.startTime) / duration; [self.context updateInteractiveTransition:complete]; }

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Invalidate when animation ends or gesture begins [self.displayLink invalidate]

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Build better transitions by using the principles of animation, and always interactive transitions

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Thank you @eallam

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Credits The 12 Principles GIFs by Vincenzo Lodigiani the12principles.tumblr.com Banana Fingers Photo: flic.kr/p/9KUF1r "Transitional Interfaces" by Pasquale D'Silva "Animated UI Transitions and Perception of Time"