使用 UIDynamicBehaviors 使用真實物理進行陰影過渡
此示例顯示如何使用類似於 iOS 的通知螢幕的真實世界物理進行互動式演示過渡。
https://i.stack.imgur.com/j0oBa.gif
首先，我們需要一個呈現檢視控制器，陰影將出現在上面。這個檢視控制器也將作為我們提供的檢視控制器的 UIViewControllerTransitioningDelegate，並將為我們的過渡提供動畫師。因此，我們將建立互動式動畫師的例項（一個用於呈現，一個用於解僱）。我們還將建立一個陰影檢視控制器的例項，在本例中，它只是一個帶標籤的檢視控制器。因為我們想要相同的平移手勢來驅動整個互動，所以我們將對呈現檢視控制器和陰影的引用傳遞給我們的互動式動畫師。
迅速
class ViewController: UIViewController
{
var presentingAnimator: ShadeAnimator!
var dismissingAnimator: ShadeAnimator!
let shadeVC = ShadeViewController()
lazy var label: UILabel =
{
let label = UILabel()
label.textColor = .blue
label.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(label)
label.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).isActive = true
label.centerYAnchor.constraint(equalTo: self.view.centerYAnchor).isActive = true
return label
}()
override func viewDidLoad()
{
super.viewDidLoad()
label.text = "Swipe Down From Top"
presentingAnimator = ShadeAnimator(isAppearing: true, presentingVC: self, presentedVC: shadeVC, transitionDelegate: self)
dismissingAnimator = ShadeAnimator(isAppearing: false, presentingVC: self, presentedVC: shadeVC, transitionDelegate: self)
}
}
extension ViewController: UIViewControllerTransitioningDelegate
{
func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning?
{
return EmptyAnimator()
}
func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning?
{
return EmptyAnimator()
}
func interactionControllerForPresentation(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning?
{
return presentingAnimator
}
func interactionControllerForDismissal(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning?
{
return dismissingAnimator
}
}
Objective-C
@interface ObjCViewController () <UIViewControllerTransitioningDelegate>
@property (nonatomic, strong) ShadeAnimator *presentingAnimator;
@property (nonatomic, strong) ShadeAnimator *dismissingAnimator;
@property (nonatomic, strong) UILabel *label;
@property (nonatomic, strong) ShadeViewController *shadeVC;
@end
@implementation ObjCViewController
- (void)viewDidLoad
{
[super viewDidLoad];
self.label.text = @"Swipe Down From Top";
self.shadeVC = [[ShadeViewController alloc] init];
self.presentingAnimator = [[ShadeAnimator alloc] initWithIsAppearing:YES presentingVC:self presentedVC:self.shadeVC transitionDelegate:self];
self.dismissingAnimator = [[ShadeAnimator alloc] initWithIsAppearing:NO presentingVC:self presentedVC:self.shadeVC transitionDelegate:self];
}
- (UILabel *)label
{
if (!_label)
{
_label = [[UILabel alloc] init];
_label.textColor = [UIColor blueColor];
_label.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:_label];
[_label.centerXAnchor constraintEqualToAnchor:self.view.centerXAnchor].active = YES;
[_label.centerYAnchor constraintEqualToAnchor:self.view.centerYAnchor].active = YES;
}
return _label;
}
#pragma mark - UIViewControllerTransitioningDelegate
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source
{
return [[EmptyAnimator alloc] init];
}
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed
{
return [[EmptyAnimator alloc] init];
}
- (id<UIViewControllerInteractiveTransitioning>)interactionControllerForPresentation:(id<UIViewControllerAnimatedTransitioning>)animator
{
return self.presentingAnimator;
}
- (id<UIViewControllerInteractiveTransitioning>)interactionControllerForDismissal:(id<UIViewControllerAnimatedTransitioning>)animator
{
return self.dismissingAnimator;
}
@end
我們真的只想通過互動式過渡來呈現我們的陰影但是由於 UIViewControllerTransitioningDelegate 如何工作如果我們不返回常規動畫控制器，我們的互動式控制器將永遠不會被使用。因此我們創造了一個符合 UIViewControllerAnimatedTransitioning 的 EmptyAnimator 類。
迅速
class EmptyAnimator: NSObject
{
}
extension EmptyAnimator: UIViewControllerAnimatedTransitioning
{
func animateTransition(using transitionContext: UIViewControllerContextTransitioning)
{
}
func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval
{
return 0.0
}
}
Objective-C
@implementation EmptyAnimator
- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
{
}
- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext
{
return 0.0;
}
@end
最後我們需要實際建立 ShadeAnimator，它是 UIDynamicBehavior 的子類，符合 UIViewControllerInteractiveTransitioning。
迅速
class ShadeAnimator: UIDynamicBehavior
{
// Whether we are presenting or dismissing
let isAppearing: Bool
// The view controller that is not the shade
weak var presentingVC: UIViewController?
// The view controller that is the shade
weak var presentedVC: UIViewController?
// The delegate will vend the animator
weak var transitionDelegate: UIViewControllerTransitioningDelegate?
// Feedback generator for haptics on collisions
let impactFeedbackGenerator = UIImpactFeedbackGenerator(style: .light)
// The context given to the animator at the start of the transition
var transitionContext: UIViewControllerContextTransitioning?
// Time limit of the dynamic part of the animation
var finishTime: TimeInterval = 4.0
// The Pan Gesture that drives the transition. Not using EdgePan because triggers Notifications screen
lazy var pan: UIPanGestureRecognizer =
{
let pan = UIPanGestureRecognizer(target: self, action: #selector(self.handlePan(sender:)))
return pan
}()
// The dynamic animator that we add `ShadeAnimator` to
lazy var animator: UIDynamicAnimator! =
{
let animator = UIDynamicAnimator(referenceView: self.transitionContext!.containerView)
return animator
}()
// init with all of our dependencies
init(isAppearing: Bool, presentingVC: UIViewController, presentedVC: UIViewController, transitionDelegate: UIViewControllerTransitioningDelegate)
{
self.isAppearing = isAppearing
self.presentingVC = presentingVC
self.presentedVC = presentedVC
self.transitionDelegate = transitionDelegate
super.init()
self.impactFeedbackGenerator.prepare()
if isAppearing
{
self.presentingVC?.view.addGestureRecognizer(pan)
}
else
{
self.presentedVC?.view.addGestureRecognizer(pan)
}
}
// Setup and moves shade view controller to just above screen if appearing
func setupViewsForTransition(with transitionContext: UIViewControllerContextTransitioning)
{
// Get relevant views and view controllers from transitionContext
guard let fromVC = transitionContext.viewController(forKey: .from),
let toVC = transitionContext.viewController(forKey: .to),
let toView = toVC.view else { return }
let containerView = transitionContext.containerView
// Hold refrence to transitionContext to notify it of completion
self.transitionContext = transitionContext
if isAppearing
{
// Position toView just off-screen
let fromViewInitialFrame = transitionContext.initialFrame(for: fromVC)
var toViewInitialFrame = toView.frame
toViewInitialFrame.origin.y -= toViewInitialFrame.height
toViewInitialFrame.origin.x = fromViewInitialFrame.width * 0.5 - toViewInitialFrame.width * 0.5
toView.frame = toViewInitialFrame
containerView.addSubview(toView)
}
else
{
fromVC.view.addGestureRecognizer(pan)
}
}
// Handles the entire interaction from presenting/dismissing to completion
func handlePan(sender: UIPanGestureRecognizer)
{
let location = sender.location(in: transitionContext?.containerView)
let velocity = sender.velocity(in: transitionContext?.containerView)
let fromVC = transitionContext?.viewController(forKey: .from)
let toVC = transitionContext?.viewController(forKey: .to)
let touchStartHeight: CGFloat = 90.0
let touchLocationFromBottom: CGFloat = 20.0
switch sender.state
{
case .began:
let beginLocation = sender.location(in: sender.view)
if isAppearing
{
guard beginLocation.y <= touchStartHeight,
let presentedVC = self.presentedVC else { break }
presentedVC.modalPresentationStyle = .custom
presentedVC.transitioningDelegate = transitionDelegate
presentingVC?.present(presentedVC, animated: true)
}
else
{
guard beginLocation.y >= (sender.view?.frame.height ?? 0.0) - touchStartHeight else { break }
presentedVC?.dismiss(animated: true)
}
case .changed:
guard let view = isAppearing ? toVC?.view : fromVC?.view else { return }
UIView.animate(withDuration: 0.2)
{
view.frame.origin.y = location.y - view.bounds.height + touchLocationFromBottom
}
transitionContext?.updateInteractiveTransition(view.frame.maxY / view.frame.height
)
case .ended, .cancelled:
guard let view = isAppearing ? toVC?.view : fromVC?.view else { return }
let isCancelled = isAppearing ? (velocity.y < 0.5 || view.center.y < 0.0) : (velocity.y > 0.5 || view.center.y > 0.0)
addAttachmentBehavior(with: view, isCancelled: isCancelled)
addCollisionBehavior(with: view)
addItemBehavior(with: view)
animator.addBehavior(self)
animator.delegate = self
self.action =
{ [weak self] in
guard let strongSelf = self else { return }
if strongSelf.animator.elapsedTime > strongSelf.finishTime
{
strongSelf.animator.removeAllBehaviors()
}
else
{
strongSelf.transitionContext?.updateInteractiveTransition(view.frame.maxY / view.frame.height
)
}
}
default:
break
}
}
// Add collision behavior that causes bounce when finished
func addCollisionBehavior(with view: UIView)
{
let collisionBehavior = UICollisionBehavior(items: [view])
let insets = UIEdgeInsets(top: -view.bounds.height, left: 0.0, bottom: 0.0, right: 0.0)
collisionBehavior.setTranslatesReferenceBoundsIntoBoundary(with: insets)
collisionBehavior.collisionDelegate = self
self.addChildBehavior(collisionBehavior)
}
// Add attachment behavior that pulls shade either to top or bottom
func addAttachmentBehavior(with view: UIView, isCancelled: Bool)
{
let anchor: CGPoint
switch (isAppearing, isCancelled)
{
case (true, true), (false, false):
anchor = CGPoint(x: view.center.x, y: -view.frame.height)
case (true, false), (false, true):
anchor = CGPoint(x: view.center.x, y: view.frame.height)
}
let attachmentBehavior = UIAttachmentBehavior(item: view, attachedToAnchor: anchor)
attachmentBehavior.damping = 0.1
attachmentBehavior.frequency = 3.0
attachmentBehavior.length = 0.5 * view.frame.height
self.addChildBehavior(attachmentBehavior)
}
// Makes view more bouncy
func addItemBehavior(with view: UIView)
{
let itemBehavior = UIDynamicItemBehavior(items: [view])
itemBehavior.allowsRotation = false
itemBehavior.elasticity = 0.6
self.addChildBehavior(itemBehavior)
}
}
extension ShadeAnimator: UIDynamicAnimatorDelegate
{
// Determines transition has ended
func dynamicAnimatorDidPause(_ animator: UIDynamicAnimator)
{
guard let transitionContext = self.transitionContext else { return }
let fromVC = transitionContext.viewController(forKey: .from)
let toVC = transitionContext.viewController(forKey: .to)
guard let view = isAppearing ? toVC?.view : fromVC?.view else { return }
switch (view.center.y < 0.0, isAppearing)
{
case (true, true), (true, false):
view.removeFromSuperview()
transitionContext.finishInteractiveTransition()
transitionContext.completeTransition(!isAppearing)
case (false, true):
toVC?.view.frame = transitionContext.finalFrame(for: toVC!)
transitionContext.finishInteractiveTransition()
transitionContext.completeTransition(true)
case (false, false):
fromVC?.view.frame = transitionContext.initialFrame(for: fromVC!)
transitionContext.cancelInteractiveTransition()
transitionContext.completeTransition(false)
}
childBehaviors.forEach { removeChildBehavior($0) }
animator.removeAllBehaviors()
self.animator = nil
self.transitionContext = nil
}
}
extension ShadeAnimator: UICollisionBehaviorDelegate
{
// Triggers haptics
func collisionBehavior(_ behavior: UICollisionBehavior, beganContactFor item: UIDynamicItem, withBoundaryIdentifier identifier: NSCopying?, at p: CGPoint)
{
guard p.y > 0.0 else { return }
impactFeedbackGenerator.impactOccurred()
}
}
extension ShadeAnimator: UIViewControllerInteractiveTransitioning
{
// Starts transition
func startInteractiveTransition(_ transitionContext: UIViewControllerContextTransitioning)
{
setupViewsForTransition(with: transitionContext)
}
}
Objective-C
@interface ShadeAnimator() <UIDynamicAnimatorDelegate, UICollisionBehaviorDelegate>
@property (nonatomic, assign) BOOL isAppearing;
@property (nonatomic, weak) UIViewController *presentingVC;
@property (nonatomic, weak) UIViewController *presentedVC;
@property (nonatomic, weak) NSObject<UIViewControllerTransitioningDelegate> *transitionDelegate;
@property (nonatomic, strong) UIImpactFeedbackGenerator *impactFeedbackGenerator;
@property (nonatomic, strong) id<UIViewControllerContextTransitioning> transitionContext;
@property (nonatomic, assign) NSTimeInterval finishTime;
@property (nonatomic, strong) UIPanGestureRecognizer *pan;
@property (nonatomic, strong) UIDynamicAnimator *animator;
@end
@implementation ShadeAnimator
- (instancetype)initWithIsAppearing:(BOOL)isAppearing presentingVC:(UIViewController *)presentingVC presentedVC:(UIViewController *)presentedVC transitionDelegate:(id<UIViewControllerTransitioningDelegate>)transitionDelegate
{
self = [super init];
if (self)
{
_isAppearing = isAppearing;
_presentingVC = presentingVC;
_presentedVC = presentedVC;
_transitionDelegate = transitionDelegate;
_impactFeedbackGenerator = [[UIImpactFeedbackGenerator alloc]initWithStyle:UIImpactFeedbackStyleLight];
[_impactFeedbackGenerator prepare];
if (_isAppearing)
{
[_presentingVC.view addGestureRecognizer:self.pan];
}
else
{
[_presentedVC.view addGestureRecognizer:self.pan];
}
}
return self;
}
#pragma mark - Lazy Init
- (UIPanGestureRecognizer *)pan
{
if (!_pan)
{
_pan = [[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(handlePan:)];
}
return _pan;
}
- (UIDynamicAnimator *)animator
{
if (!_animator)
{
_animator = [[UIDynamicAnimator alloc]initWithReferenceView:self.transitionContext.containerView];
}
return _animator;
}
#pragma mark - Setup
- (void)setupViewForTransitionWithContext:(id<UIViewControllerContextTransitioning>)transitionContext
{
UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
UIView *toView = toVC.view;
UIView *containerView = transitionContext.containerView;
self.transitionContext = transitionContext;
if (self.isAppearing)
{
CGRect fromViewInitialFrame = [transitionContext initialFrameForViewController:fromVC];
CGRect toViewInitialFrame = toView.frame;
toViewInitialFrame.origin.y -= CGRectGetHeight(toViewInitialFrame);
toViewInitialFrame.origin.x = CGRectGetWidth(fromViewInitialFrame) * 0.5 - CGRectGetWidth(toViewInitialFrame) * 0.5;
[containerView addSubview:toView];
}
else
{
[fromVC.view addGestureRecognizer:self.pan];
}
}
#pragma mark - Gesture
- (void)handlePan:(UIPanGestureRecognizer *)sender
{
CGPoint location = [sender locationInView:self.transitionContext.containerView];
CGPoint velocity = [sender velocityInView:self.transitionContext.containerView];
UIViewController *fromVC = [self.transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
UIViewController *toVC = [self.transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
CGFloat touchStartHeight = 90.0;
CGFloat touchLocationFromBottom = 20.0;
if (sender.state == UIGestureRecognizerStateBegan)
{
CGPoint beginLocation = [sender locationInView:sender.view];
if (self.isAppearing)
{
if (beginLocation.y <= touchStartHeight)
{
self.presentedVC.modalPresentationStyle = UIModalPresentationCustom;
self.presentedVC.transitioningDelegate = self.transitionDelegate;
[self.presentingVC presentViewController:self.presentedVC animated:YES completion:nil];
}
}
else
{
if (beginLocation.y >= [sender locationInView:sender.view].y - touchStartHeight)
{
[self.presentedVC dismissViewControllerAnimated:true completion:nil];
}
}
}
else if (sender.state == UIGestureRecognizerStateChanged)
{
UIView *view = self.isAppearing ? toVC.view : fromVC.view;
[UIView animateWithDuration:0.2 animations:^{
CGRect frame = view.frame;
frame.origin.y = location.y - CGRectGetHeight(view.bounds) + touchLocationFromBottom;
view.frame = frame;
}];
[self.transitionContext updateInteractiveTransition:CGRectGetMaxY(view.frame) / CGRectGetHeight(view.frame)];
}
else if (sender.state == UIGestureRecognizerStateEnded || sender.state == UIGestureRecognizerStateCancelled)
{
UIView *view = self.isAppearing ? toVC.view : fromVC.view;
BOOL isCancelled = self.isAppearing ? (velocity.y < 0.5 || view.center.y < 0.0) : (velocity.y > 0.5 || view.center.y > 0.0);
[self addAttachmentBehaviorWithView:view isCancelled:isCancelled];
[self addCollisionBehaviorWithView:view];
[self addItemBehaviorWithView:view];
[self.animator addBehavior:self];
self.animator.delegate = self;
__weak ShadeAnimator *weakSelf = self;
self.action =
^{
if (weakSelf.animator.elapsedTime > weakSelf.finishTime)
{
[weakSelf.animator removeAllBehaviors];
}
else
{
[weakSelf.transitionContext updateInteractiveTransition:CGRectGetMaxY(view.frame) / CGRectGetHeight(view.frame)];
}
};
}
}
#pragma mark - UIViewControllerInteractiveTransitioning
- (void)startInteractiveTransition:(id<UIViewControllerContextTransitioning>)transitionContext
{
[self setupViewForTransitionWithContext:transitionContext];
}
#pragma mark - Behaviors
- (void)addCollisionBehaviorWithView:(UIView *)view
{
UICollisionBehavior *collisionBehavior = [[UICollisionBehavior alloc]initWithItems:@[view]];
UIEdgeInsets insets = UIEdgeInsetsMake(-CGRectGetHeight(view.bounds), 0.0, 0.0, 0.0);
[collisionBehavior setTranslatesReferenceBoundsIntoBoundaryWithInsets:insets];
collisionBehavior.collisionDelegate = self;
[self addChildBehavior:collisionBehavior];
}
- (void)addItemBehaviorWithView:(UIView *)view
{
UIDynamicItemBehavior *itemBehavior = [[UIDynamicItemBehavior alloc]initWithItems:@[view]];
itemBehavior.allowsRotation = NO;
itemBehavior.elasticity = 0.6;
[self addChildBehavior:itemBehavior];
}
- (void)addAttachmentBehaviorWithView:(UIView *)view isCancelled:(BOOL)isCancelled
{
CGPoint anchor;
if ((self.isAppearing && isCancelled) || (!self.isAppearing && isCancelled))
{
anchor = CGPointMake(view.center.x, -CGRectGetHeight(view.frame));
}
else
{
anchor = CGPointMake(view.center.x, -CGRectGetHeight(view.frame));
}
UIAttachmentBehavior *attachmentBehavior = [[UIAttachmentBehavior alloc]initWithItem:view attachedToAnchor:anchor];
attachmentBehavior.damping = 0.1;
attachmentBehavior.frequency = 3.0;
attachmentBehavior.length = 0.5 * CGRectGetHeight(view.frame);
[self addChildBehavior:attachmentBehavior];
}
#pragma mark - UICollisionBehaviorDelegate
- (void)collisionBehavior:(UICollisionBehavior *)behavior beganContactForItem:(id<UIDynamicItem>)item withBoundaryIdentifier:(id<NSCopying>)identifier atPoint:(CGPoint)p
{
if (p.y > 0.0)
{
[self.impactFeedbackGenerator impactOccurred];
}
}
#pragma mark - UIDynamicAnimatorDelegate
- (void)dynamicAnimatorDidPause:(UIDynamicAnimator *)animator
{
UIViewController *fromVC = [self.transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
UIViewController *toVC = [self.transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
UIView *view = self.isAppearing ? toVC.view : fromVC.view;
if (view.center.y < 0.0 && (self.isAppearing || !self.isAppearing))
{
[view removeFromSuperview];
[self.transitionContext finishInteractiveTransition];
[self.transitionContext completeTransition:!self.isAppearing];
}
else if (view.center.y >= 0.0 && self.isAppearing)
{
toVC.view.frame = [self.transitionContext finalFrameForViewController:toVC];
[self.transitionContext finishInteractiveTransition];
[self.transitionContext completeTransition:YES];
}
else
{
fromVC.view.frame = [self.transitionContext initialFrameForViewController:fromVC];
[self.transitionContext cancelInteractiveTransition];
[self.transitionContext completeTransition:NO];
}
for (UIDynamicBehavior *behavior in self.childBehaviors)
{
[self removeChildBehavior:behavior];
}
[animator removeAllBehaviors];
self.animator = nil;
self.transitionContext = nil;
}
@end
當平移手勢開始時，動畫師觸發轉換的開始。只需在手勢發生變化時移動檢視。但是當手勢結束時，UIDynamicBehaviors 確定是否應該完成或取消過渡。為此，它使用附件和碰撞行為。有關更多資訊，請參閱 2013 WWDC 會議“使用 UIKit Dynamics 的高階技術” 。