iOS
UIKit Dynamics

Introduktion

Anmärkningar

label.frame = CGRect(x: 0.0, y: 0.0, width: label.intrinsicContentSize.width, height: label.intrinsicContentSize.height)
dynamicAnimator.updateItem(usingCurrentState: label)

self.label.frame = CGRectMake(0.0, 0.0, self.label.intrinsicContentSize.width, self.label.intrinsicContentSize.height);
[self.dynamicAnimator updateItemUsingCurrentState: self.label];

Det fallande torget

Låt oss rita en fyrkant i mitten av vår vy och få den att falla till botten och stoppa vid den nedre kanten som kolliderar med skärmens bottengräns.

@IBOutlet var animationView: UIView!
var squareView:UIView!
var collision: UICollisionBehavior!
var animator: UIDynamicAnimator!
var gravity: UIGravityBehavior!

override func viewDidLoad() {
    super.viewDidLoad()
    let squareSize = CGSize(width: 30.0, height: 30.0)
    let centerPoint = CGPoint(x: self.animationView.bounds.midX - (squareSize.width/2), y: self.animationView.bounds.midY - (squareSize.height/2))
    let frame = CGRect(origin: centerPoint, size: squareSize)
    squareView = UIView(frame: frame)
    squareView.backgroundColor = UIColor.orangeColor()
    animationView.addSubview(squareView)
    animator = UIDynamicAnimator(referenceView: view)
    gravity = UIGravityBehavior(items: [squareView])
    animator.addBehavior(gravity)
    collision = UICollisionBehavior(items: [square])
    collision.translatesReferenceBoundsIntoBoundary = true
    animator.addBehavior(collision)
}

Flickvy baserat på gesthastighet

Det här exemplet visar hur du kan se en spårning av en pan-gest och avvika på ett fysikbaserat sätt.

Snabb

class ViewController: UIViewController
{
    // Adjust to change speed of view from flick
    let magnitudeMultiplier: CGFloat = 0.0008
    
    lazy var dynamicAnimator: UIDynamicAnimator =
    {
        let dynamicAnimator = UIDynamicAnimator(referenceView: self.view)
        return dynamicAnimator
    }()

    lazy var gravity: UIGravityBehavior =
    {
        let gravity = UIGravityBehavior(items: [self.orangeView])
        return gravity
    }()
    
    lazy var collision: UICollisionBehavior =
    {
        let collision = UICollisionBehavior(items: [self.orangeView])
        collision.translatesReferenceBoundsIntoBoundary = true
        return collision
    }()
    
    lazy var orangeView: UIView =
    {
        let widthHeight: CGFloat = 40.0
        let orangeView = UIView(frame: CGRect(x: 0.0, y: 0.0, width: widthHeight, height: widthHeight))
        orangeView.backgroundColor = UIColor.orange
        self.view.addSubview(orangeView)
        return orangeView
    }()
    
    lazy var panGesture: UIPanGestureRecognizer =
    {
        let panGesture = UIPanGestureRecognizer(target: self, action: #selector(self.handlePan(sender:)))
        return panGesture
    }()
    
    lazy var attachment: UIAttachmentBehavior =
    {
        let attachment = UIAttachmentBehavior(item: self.orangeView, attachedToAnchor: .zero)
        return attachment
    }()

    override func viewDidLoad()
    {
        super.viewDidLoad()
        dynamicAnimator.addBehavior(gravity)
        dynamicAnimator.addBehavior(collision)
        orangeView.addGestureRecognizer(panGesture)
    }
    
    override func viewDidLayoutSubviews()
    {
        super.viewDidLayoutSubviews()
        orangeView.center = view.center
        dynamicAnimator.updateItem(usingCurrentState: orangeView)
    }
    
    func handlePan(sender: UIPanGestureRecognizer)
    {
        let location = sender.location(in: view)
        let velocity = sender.velocity(in: view)
        let magnitude = sqrt((velocity.x * velocity.x) + (velocity.y * velocity.y))
        switch sender.state
        {
        case .began:
            attachment.anchorPoint = location
            dynamicAnimator.addBehavior(attachment)
        case .changed:
            attachment.anchorPoint = location
        case .cancelled, .ended, .failed, .possible:
            let push = UIPushBehavior(items: [self.orangeView], mode: .instantaneous)
            push.pushDirection = CGVector(dx: velocity.x, dy: velocity.y)
            push.magnitude = magnitude * magnitudeMultiplier
            dynamicAnimator.removeBehavior(attachment)
            dynamicAnimator.addBehavior(push)
        }
    }
}

Objective-C

@interface ViewController ()

@property (nonatomic, assign) CGFloat magnitudeMultiplier;
@property (nonatomic, strong) UIDynamicAnimator *dynamicAnimator;
@property (nonatomic, strong) UIGravityBehavior *gravity;
@property (nonatomic, strong) UICollisionBehavior *collision;
@property (nonatomic, strong) UIView *orangeView;
@property (nonatomic, strong) UIPanGestureRecognizer *panGesture;
@property (nonatomic, strong) UIAttachmentBehavior *attachment;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self.dynamicAnimator addBehavior:self.gravity];
    [self.dynamicAnimator addBehavior:self.collision];
    [self.orangeView addGestureRecognizer:self.panGesture];
    // Adjust to change speed of view from flick
    self.magnitudeMultiplier = 0.0008f;
}

- (void)viewDidLayoutSubviews
{
    [super viewDidLayoutSubviews];
    self.orangeView.center = self.view.center;
    [self.dynamicAnimator updateItemUsingCurrentState:self.orangeView];
}

- (void)handlePan:(UIPanGestureRecognizer *)sender
{
    CGPoint location = [sender locationInView:self.view];
    CGPoint velocity = [sender velocityInView:self.view];
    CGFloat magnitude = sqrt((velocity.x * velocity.x) + (velocity.y * velocity.y));
    if (sender.state == UIGestureRecognizerStateBegan)
    {
        self.attachment.anchorPoint = location;
        [self.dynamicAnimator addBehavior:self.attachment];
    }
    else if (sender.state == UIGestureRecognizerStateChanged)
    {
        self.attachment.anchorPoint = location;
    }
    else if (sender.state == UIGestureRecognizerStateCancelled ||
             sender.state == UIGestureRecognizerStateEnded ||
             sender.state == UIGestureRecognizerStateFailed ||
             sender.state == UIGestureRecognizerStatePossible)
    {
        UIPushBehavior *push = [[UIPushBehavior alloc] initWithItems:@[self.orangeView] mode:UIPushBehaviorModeInstantaneous];
        push.pushDirection = CGVectorMake(velocity.x, velocity.y);
        push.magnitude = magnitude * self.magnitudeMultiplier;
        [self.dynamicAnimator removeBehavior:self.attachment];
        [self.dynamicAnimator addBehavior:push];
    }
}

#pragma mark - Lazy Init
- (UIDynamicAnimator *)dynamicAnimator
{
    if (!_dynamicAnimator)
    {
        _dynamicAnimator = [[UIDynamicAnimator alloc]initWithReferenceView:self.view];
    }
    return _dynamicAnimator;
}

- (UIGravityBehavior *)gravity
{
    if (!_gravity)
    {
        _gravity = [[UIGravityBehavior alloc]initWithItems:@[self.orangeView]];
    }
    return _gravity;
}

- (UICollisionBehavior *)collision
{
    if (!_collision)
    {
        _collision = [[UICollisionBehavior alloc]initWithItems:@[self.orangeView]];
        _collision.translatesReferenceBoundsIntoBoundary = YES;
    }
    return _collision;
}

- (UIView *)orangeView
{
    if (!_orangeView)
    {
        CGFloat widthHeight = 40.0f;
        _orangeView = [[UIView alloc]initWithFrame:CGRectMake(0.0, 0.0, widthHeight, widthHeight)];
        _orangeView.backgroundColor = [UIColor orangeColor];
        [self.view addSubview:_orangeView];
    }
    return _orangeView;
}

- (UIPanGestureRecognizer *)panGesture
{
    if (!_panGesture)
    {
        _panGesture = [[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(handlePan:)];
    }
    return _panGesture;
}

- (UIAttachmentBehavior *)attachment
{
    if (!_attachment)
    {
        _attachment = [[UIAttachmentBehavior alloc]initWithItem:self.orangeView attachedToAnchor:CGPointZero];
    }
    return _attachment;
}

@end

"Klibbiga hörn" -effekt med hjälp av UIFieldBehaviors

Det här exemplet visar hur man uppnår en effekt som liknar FaceTime där en vy lockas till punkten när den kommer in i en viss region, i detta fall två regioner en topp och botten.

Snabb

class ViewController: UIViewController
{
    lazy var dynamicAnimator: UIDynamicAnimator =
    {
        let dynamicAnimator = UIDynamicAnimator(referenceView: self.view)
        return dynamicAnimator
    }()
    
    lazy var collision: UICollisionBehavior =
    {
        let collision = UICollisionBehavior(items: [self.orangeView])
        collision.translatesReferenceBoundsIntoBoundary = true
        return collision
    }()
    
    lazy var fieldBehaviors: [UIFieldBehavior] =
    {
        var fieldBehaviors = [UIFieldBehavior]()
        for _ in 0 ..< 2
        {
            let field = UIFieldBehavior.springField()
            field.addItem(self.orangeView)
            fieldBehaviors.append(field)
        }
        return fieldBehaviors
    }()
    
    lazy var itemBehavior: UIDynamicItemBehavior =
    {
        let itemBehavior = UIDynamicItemBehavior(items: [self.orangeView])
        // Adjust these values to change the "stickiness" of the view
        itemBehavior.density = 0.01
        itemBehavior.resistance = 10
        itemBehavior.friction = 0.0
        itemBehavior.allowsRotation = false
        return itemBehavior
    }()
    
    lazy var orangeView: UIView =
    {
        let widthHeight: CGFloat = 40.0
        let orangeView = UIView(frame: CGRect(x: 0.0, y: 0.0, width: widthHeight, height: widthHeight))
        orangeView.backgroundColor = UIColor.orange
        self.view.addSubview(orangeView)
        return orangeView
    }()
    
    lazy var panGesture: UIPanGestureRecognizer =
    {
        let panGesture = UIPanGestureRecognizer(target: self, action: #selector(self.handlePan(sender:)))
        return panGesture
    }()
    
    lazy var attachment: UIAttachmentBehavior =
    {
        let attachment = UIAttachmentBehavior(item: self.orangeView, attachedToAnchor: .zero)
        return attachment
    }()

    override func viewDidLoad()
    {
        super.viewDidLoad()
        dynamicAnimator.addBehavior(collision)
        dynamicAnimator.addBehavior(itemBehavior)
        for field in fieldBehaviors
        {
            dynamicAnimator.addBehavior(field)
        }
        
        orangeView.addGestureRecognizer(panGesture)
    }
    
    override func viewDidLayoutSubviews()
    {
        super.viewDidLayoutSubviews()
        
        orangeView.center = view.center
        dynamicAnimator.updateItem(usingCurrentState: orangeView)
        
        for (index, field) in fieldBehaviors.enumerated()
        {
            field.position = CGPoint(x: view.bounds
                .midX, y:  view.bounds.height * (0.25 + 0.5 * CGFloat(index)))
            field.region = UIRegion(size: CGSize(width: view.bounds.width, height: view.bounds.height * 0.5))
        }
    }
    
    func handlePan(sender: UIPanGestureRecognizer)
    {
        let location = sender.location(in: view)
        let velocity = sender.velocity(in: view)
        switch sender.state
        {
        case .began:
            attachment.anchorPoint = location
            dynamicAnimator.addBehavior(attachment)
        case .changed:
            attachment.anchorPoint = location
        case .cancelled, .ended, .failed, .possible:
            itemBehavior.addLinearVelocity(velocity, for: self.orangeView)
            dynamicAnimator.removeBehavior(attachment)
        }
    }
}

Objective-C

@interface ViewController ()

@property (nonatomic, strong) UIDynamicAnimator *dynamicAnimator;
@property (nonatomic, strong) UICollisionBehavior *collision;
@property (nonatomic, strong) UIAttachmentBehavior *attachment;
@property (nonatomic, strong) UIDynamicItemBehavior *itemBehavior;
@property (nonatomic, strong) NSArray <UIFieldBehavior *> *fieldBehaviors;
@property (nonatomic, strong) UIView *orangeView;
@property (nonatomic, strong) UIPanGestureRecognizer *panGesture;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self.dynamicAnimator addBehavior:self.collision];
    [self.dynamicAnimator addBehavior:self.itemBehavior];
    for (UIFieldBehavior *field in self.fieldBehaviors)
    {
        [self.dynamicAnimator addBehavior:field];
    }
    
    [self.orangeView addGestureRecognizer:self.panGesture];
}

- (void)viewDidLayoutSubviews
{
    [super viewDidLayoutSubviews];
    self.orangeView.center = self.view.center;
    [self.dynamicAnimator updateItemUsingCurrentState:self.orangeView];
    
    for (NSInteger i = 0; i < self.fieldBehaviors.count; i++)
    {
        UIFieldBehavior *field = self.fieldBehaviors[i];
        field.position = CGPointMake(CGRectGetMidX(self.view.bounds), CGRectGetHeight(self.view.bounds) * (0.25f + 0.5f * i));
        field.region = [[UIRegion alloc]initWithSize:CGSizeMake(CGRectGetWidth(self.view.bounds), CGRectGetHeight(self.view.bounds) * 0.5)];
    }
}

- (void)handlePan:(UIPanGestureRecognizer *)sender
{
    CGPoint location = [sender locationInView:self.view];
    CGPoint velocity = [sender velocityInView:self.view];
    if (sender.state == UIGestureRecognizerStateBegan)
    {
        self.attachment.anchorPoint = location;
        [self.dynamicAnimator addBehavior:self.attachment];
    }
    else if (sender.state == UIGestureRecognizerStateChanged)
    {
        self.attachment.anchorPoint = location;
    }
    else if (sender.state == UIGestureRecognizerStateCancelled ||
             sender.state == UIGestureRecognizerStateEnded ||
             sender.state == UIGestureRecognizerStateFailed ||
             sender.state == UIGestureRecognizerStatePossible)
    {
        [self.itemBehavior addLinearVelocity:velocity forItem:self.orangeView];
        [self.dynamicAnimator removeBehavior:self.attachment];
    }
}

#pragma mark - Lazy Init
- (UIDynamicAnimator *)dynamicAnimator
{
    if (!_dynamicAnimator)
    {
        _dynamicAnimator = [[UIDynamicAnimator alloc]initWithReferenceView:self.view];
    }
    return _dynamicAnimator;
}

- (UICollisionBehavior *)collision
{
    if (!_collision)
    {
        _collision = [[UICollisionBehavior alloc]initWithItems:@[self.orangeView]];
        _collision.translatesReferenceBoundsIntoBoundary = YES;
    }
    return _collision;
}

- (NSArray <UIFieldBehavior *> *)fieldBehaviors
{
    if (!_fieldBehaviors)
    {
        NSMutableArray *fields = [[NSMutableArray alloc]init];
        for (NSInteger i =  0; i < 2; i++)
        {
            UIFieldBehavior *field = [UIFieldBehavior springField];
            [field addItem:self.orangeView];
            [fields addObject:field];
        }
        _fieldBehaviors = fields;
    }
    return _fieldBehaviors;
}

- (UIDynamicItemBehavior *)itemBehavior
{
    if (!_itemBehavior)
    {
        _itemBehavior = [[UIDynamicItemBehavior alloc]initWithItems:@[self.orangeView]];
        // Adjust these values to change the "stickiness" of the view
        _itemBehavior.density = 0.01;
        _itemBehavior.resistance = 10;
        _itemBehavior.friction = 0.0;
        _itemBehavior.allowsRotation = NO;
    }
    return _itemBehavior;
}

- (UIView *)orangeView
{
    if (!_orangeView)
    {
        CGFloat widthHeight = 40.0f;
        _orangeView = [[UIView alloc]initWithFrame:CGRectMake(0.0, 0.0, widthHeight, widthHeight)];
        _orangeView.backgroundColor = [UIColor orangeColor];
        [self.view addSubview:_orangeView];
    }
    return _orangeView;
}

- (UIPanGestureRecognizer *)panGesture
{
    if (!_panGesture)
    {
        _panGesture = [[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(handlePan:)];
    }
    return _panGesture;
}

- (UIAttachmentBehavior *)attachment
{
    if (!_attachment)
    {
        _attachment = [[UIAttachmentBehavior alloc]initWithItem:self.orangeView attachedToAnchor:CGPointZero];
    }
    return _attachment;
}

@end

För mer information om UIFieldBehaviors du se WWDC-sessionen 2015 "Nyheter i UIKit Dynamics and Visual Effects" och medföljande provkod .

UIDynamicBehavior Driven Custom Transition

Detta exempel visar hur du skapar en anpassad presentationövergång som drivs av en sammansatt UIDynamicBehavior . Vi kan börja med att skapa en presentationsvisningskontroller som kommer att presentera en modal.

Snabb

class PresentingViewController: UIViewController
{
    lazy var button: UIButton =
    {
        let button = UIButton()
        button.translatesAutoresizingMaskIntoConstraints = false
        self.view.addSubview(button)
        button.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).isActive
            = true
        button.centerYAnchor.constraint(equalTo: self.view.centerYAnchor).isActive = true
        button.setTitle("Present", for: .normal)
        button.setTextColor(UIColor.blue, for: .normal)
        
        return button
    }()
    
    override func viewDidLoad()
    {
        super.viewDidLoad()
        button.addTarget(self, action: #selector(self.didPressPresent), for: .touchUpInside)
    }
    
    func didPressPresent()
    {
        let modal = ModalViewController()
        modal.view.frame = CGRect(x: 0.0, y: 0.0, width: 200.0, height: 200.0)
        modal.modalPresentationStyle = .custom
        modal.transitioningDelegate = modal
        self.present(modal, animated: true)
    }
}

Objective-C

@interface PresentingViewController ()
@property (nonatomic, strong) UIButton *button;
@end

@implementation PresentingViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self.button addTarget:self action:@selector(didPressPresent) forControlEvents:UIControlEventTouchUpInside];
}

- (void)didPressPresent
{
    ModalViewController *modal = [[ModalViewController alloc] init];
    modal.view.frame = CGRectMake(0.0, 0.0, 200.0, 200.0);
    modal.modalPresentationStyle = UIModalPresentationCustom;
    modal.transitioningDelegate = modal;
    [self presentViewController:modal animated:YES completion:nil];
}

- (UIButton *)button
{
    if (!_button)
    {
        _button = [[UIButton alloc] init];
        _button.translatesAutoresizingMaskIntoConstraints = NO;
        [self.view addSubview:_button];
        [_button.centerXAnchor constraintEqualToAnchor:self.view.centerXAnchor].active = YES;
        [_button.centerYAnchor constraintEqualToAnchor:self.view.centerYAnchor].active = YES;
        [_button setTitle:@"Present" forState:UIControlStateNormal];
        [_button setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];
    }
    return _button;
}

@end

När man ModalViewController den nuvarande knappen skapar vi en ModalViewController och ställer dess presentationsstil på .custom och ställer dess transitionDelegate till sig själv. Detta tillåter oss att sälja en animatör som kommer att driva sin modala övergång. Vi ställer också in modal ram så att den blir mindre än hela skärmen.

Låt oss nu titta på ModalViewController :

Snabb

class ModalViewController: UIViewController
{
    lazy var button: UIButton =
    {
        let button = UIButton()
        button.translatesAutoresizingMaskIntoConstraints = false
        self.view.addSubview(button)
        button.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).isActive
         = true
        button.centerYAnchor.constraint(equalTo: self.view.centerYAnchor).isActive = true
        button.setTitle("Dismiss", for: .normal)
        button.setTitleColor(.white, for: .normal)
        
        return button
    }()
    
    override func viewDidLoad()
    {
        super.viewDidLoad()
        button.addTarget(self, action: #selector(self.didPressDismiss), for: .touchUpInside)
        view.backgroundColor = .red
        view.layer.cornerRadius = 15.0
    }
    
    func didPressDismiss()
    {
        dismiss(animated: true)
    }
}

extension ModalViewController: UIViewControllerTransitioningDelegate
{
    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning?
    {
        return DropOutAnimator(duration: 1.5, isAppearing: true)
    }
    
    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning?
    {
        return DropOutAnimator(duration: 4.0, isAppearing: false)
    }
}

Objective-C

@interface ModalViewController () <UIViewControllerTransitioningDelegate>
@property (nonatomic, strong) UIButton *button;
@end

@implementation ModalViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self.button addTarget:self action:@selector(didPressPresent) forControlEvents:UIControlEventTouchUpInside];
    self.view.backgroundColor = [UIColor redColor];
    self.view.layer.cornerRadius = 15.0f;
}

- (void)didPressPresent
{
    [self dismissViewControllerAnimated:YES completion:nil];
}

- (UIButton *)button
{
    if (!_button)
    {
        _button = [[UIButton alloc] init];
        _button.translatesAutoresizingMaskIntoConstraints = NO;
        [self.view addSubview:_button];
        [_button.centerXAnchor constraintEqualToAnchor:self.view.centerXAnchor].active = YES;
        [_button.centerYAnchor constraintEqualToAnchor:self.view.centerYAnchor].active = YES;
        [_button setTitle:@"Dismiss" forState:UIControlStateNormal];
        [_button setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];
    }
    return _button;
}

- (id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source
{
    return [[DropOutAnimator alloc]initWithDuration: 1.5 appearing:YES];
}

- (id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed
{
    return [[DropOutAnimator alloc] initWithDuration:4.0 appearing:NO];
}

@end

Här skapar vi visningskontrollern som presenteras. Eftersom ModalViewController är den egna transitioningDelegate ModalViewController är den också ansvarig för att köra ett objekt som hanterar övergångsanimationen. För oss betyder det att vidarebefordra en instans av vår sammansatta UIDynamicBehavior underklass.

Vår animatör kommer att ha två olika övergångar: en för att presentera och en för att avslå. För att presentera kommer den nuvarande visningskontrollerns vy att släppa in ovanifrån. Och för att avfärda verkar vyn svänga från ett rep och sedan släppa ut. Eftersom DropOutAnimator överensstämmer med UIViewControllerAnimatedTransitioning mesta av detta arbete att utföras i dess implementering av func animateTransition(using transitionContext: UIViewControllerContextTransitioning) .

Snabb

class DropOutAnimator: UIDynamicBehavior
{
    let duration: TimeInterval
    let isAppearing: Bool

    var transitionContext: UIViewControllerContextTransitioning?
    var hasElapsedTimeExceededDuration = false
    var finishTime: TimeInterval = 0.0
    var collisionBehavior: UICollisionBehavior?
    var attachmentBehavior: UIAttachmentBehavior?
    var animator: UIDynamicAnimator?

    init(duration: TimeInterval = 1.0,  isAppearing: Bool)
    {
        self.duration = duration
        self.isAppearing = isAppearing
        super.init()
    }
}

extension DropOutAnimator: UIViewControllerAnimatedTransitioning
{
    func animateTransition(using transitionContext: UIViewControllerContextTransitioning)
    {
        // Get relevant views and view controllers from transitionContext
        guard let fromVC = transitionContext.viewController(forKey: .from),
              let toVC = transitionContext.viewController(forKey: .to),
              let fromView = fromVC.view,
              let toView = toVC.view else { return }
    
        let containerView = transitionContext.containerView
        let duration = self.transitionDuration(using: transitionContext)
    
        // Hold refrence to transitionContext to notify it of completion
        self.transitionContext = transitionContext
    
        // Create dynamic animator
        let animator = UIDynamicAnimator(referenceView: containerView)
        animator.delegate = self
        self.animator = animator
    
        // Presenting Animation
        if self.isAppearing
        {
            fromView.isUserInteractionEnabled = false
        
            // 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)
        
            // Prevent rotation and adjust bounce
            let bodyBehavior = UIDynamicItemBehavior(items: [toView])
            bodyBehavior.elasticity = 0.7
            bodyBehavior.allowsRotation = false
        
            // Add gravity at exaggerated magnitude so animation doesn't seem slow
            let gravityBehavior = UIGravityBehavior(items: [toView])
            gravityBehavior.magnitude = 10.0
        
            // Set collision bounds to include off-screen view and have collision in center 
            // where our final view should come to rest
            let collisionBehavior = UICollisionBehavior(items: [toView])
            let insets = UIEdgeInsets(top: toViewInitialFrame.minY, left: 0.0, bottom: fromViewInitialFrame.height * 0.5 - toViewInitialFrame.height * 0.5, right: 0.0)
            collisionBehavior.setTranslatesReferenceBoundsIntoBoundary(with: insets)
            self.collisionBehavior = collisionBehavior
        
            // Keep track of finish time in case we need to end the animator befor the animator pauses
            self.finishTime = duration + (self.animator?.elapsedTime ?? 0.0)
        
            // Closure that is called after every "tick" of the animator
            // Check if we exceed duration
            self.action =
            { [weak self] in
                guard let strongSelf = self,
                  (strongSelf.animator?.elapsedTime ?? 0.0) >= strongSelf.finishTime else { return }
                strongSelf.hasElapsedTimeExceededDuration = true
                strongSelf.animator?.removeBehavior(strongSelf)
            }
        
            // `DropOutAnimator` is a composit behavior, so add child behaviors to self
            self.addChildBehavior(collisionBehavior)
            self.addChildBehavior(bodyBehavior)
            self.addChildBehavior(gravityBehavior)
        
            // Add self to dynamic animator
            self.animator?.addBehavior(self)
        }
        // Dismissing Animation
        else
        {
            // Create allow rotation and have a elastic item
            let bodyBehavior = UIDynamicItemBehavior(items: [fromView])
            bodyBehavior.elasticity = 0.8
            bodyBehavior.angularResistance = 5.0
            bodyBehavior.allowsRotation = true
        
            // Create gravity with exaggerated magnitude
            let gravityBehavior = UIGravityBehavior(items: [fromView])
            gravityBehavior.magnitude = 10.0
        
            // Collision boundary is set to have a floor just below the bottom of the screen
            let collisionBehavior = UICollisionBehavior(items: [fromView])
            let insets = UIEdgeInsets(top: 0.0, left: -1000, bottom: -225, right: -1000)
            collisionBehavior.setTranslatesReferenceBoundsIntoBoundary(with: insets)
            self.collisionBehavior = collisionBehavior
        
            // Attachment behavior so view will have effect of hanging from a rope
            let offset = UIOffset(horizontal: 70.0, vertical: fromView.bounds.height * 0.5)
            var anchorPoint = CGPoint(x: fromView.bounds.maxX - 40.0, y: fromView.bounds.minY)
            anchorPoint = containerView.convert(anchorPoint, from: fromView)
            let attachmentBehavior = UIAttachmentBehavior(item: fromView, offsetFromCenter: offset, attachedToAnchor: anchorPoint)
            attachmentBehavior.frequency = 3.0
            attachmentBehavior.damping = 3.0
            self.attachmentBehavior = attachmentBehavior
        
            // `DropOutAnimator` is a composit behavior, so add child behaviors to self
            self.addChildBehavior(collisionBehavior)
            self.addChildBehavior(bodyBehavior)
            self.addChildBehavior(gravityBehavior)
            self.addChildBehavior(attachmentBehavior)
        
            // Add self to dynamic animator
            self.animator?.addBehavior(self)
        
            // Animation has two parts part one is hanging from rope. 
            // Part two is bouncying off-screen
            // Divide duration in two
            self.finishTime = (2.0 / 3.0) * duration + (self.animator?.elapsedTime ?? 0.0)
        
             // After every "tick" of animator check if past time limit
            self.action =
            { [weak self] in
                guard let strongSelf = self,
                  (strongSelf.animator?.elapsedTime ?? 0.0) >= strongSelf.finishTime else { return }
                strongSelf.hasElapsedTimeExceededDuration = true
                strongSelf.animator?.removeBehavior(strongSelf)
            }
        }
    
    }

    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval
    {
        // Return the duration of the animation
        return self.duration
    }
}

extension DropOutAnimator: UIDynamicAnimatorDelegate
{
    func dynamicAnimatorDidPause(_ animator: UIDynamicAnimator)
    {
      // Animator has reached stasis
      if self.isAppearing
      {
            // Check if we are out of time
            if self.hasElapsedTimeExceededDuration
            {
                // Move to final positions
                let toView = self.transitionContext?.viewController(forKey: .to)?.view
                let containerView = self.transitionContext?.containerView
                toView?.center = containerView?.center ?? .zero
                self.hasElapsedTimeExceededDuration = false
            }
            
            // Clean up and call completion
            self.transitionContext?.completeTransition(!(self.transitionContext?.transitionWasCancelled ?? false))
            self.childBehaviors.forEach { self.removeChildBehavior($0) }
            animator.removeAllBehaviors()
            self.transitionContext = nil
    }
    else
    {
        if let attachmentBehavior = self.attachmentBehavior
        {
            // If we have an attachment, we are at the end of part one and start part two.
            self.removeChildBehavior(attachmentBehavior)
            self.attachmentBehavior = nil
            animator.addBehavior(self)
            let duration = self.transitionDuration(using: self.transitionContext)
            self.finishTime = 1.0 / 3.0 * duration + animator.elapsedTime
        }
        else
        {
            // Clean up and call completion
            let fromView = self.transitionContext?.viewController(forKey: .from)?.view
            let toView = self.transitionContext?.viewController(forKey: .to)?.view
            fromView?.removeFromSuperview()
            toView?.isUserInteractionEnabled = true
            self.transitionContext?.completeTransition(!(self.transitionContext?.transitionWasCancelled ?? false))
            self.childBehaviors.forEach { self.removeChildBehavior($0) }
            animator.removeAllBehaviors()
            self.transitionContext = nil
        }
    }
}
}

Objective-C

@interface ObjcDropOutAnimator() <UIDynamicAnimatorDelegate, UIViewControllerAnimatedTransitioning>
@property (nonatomic, strong) id<UIViewControllerContextTransitioning> transitionContext;
@property (nonatomic, strong) UIDynamicAnimator *animator;
@property (nonatomic, assign) NSTimeInterval finishTime;
@property (nonatomic, assign) BOOL elapsedTimeExceededDuration;
@property (nonatomic, assign, getter=isAppearing) BOOL appearing;
@property (nonatomic, assign) NSTimeInterval duration;
@property (nonatomic, strong) UIAttachmentBehavior *attachBehavior;
@property (nonatomic, strong) UICollisionBehavior * collisionBehavior;

@end

@implementation ObjcDropOutAnimator

- (instancetype)initWithDuration:(NSTimeInterval)duration appearing:(BOOL)appearing
{
    self = [super init];
    if (self)
    {
        _duration = duration;
        _appearing = appearing;
    }
    return self;
}

- (void) animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
{
    // Get relevant views and view controllers from transitionContext
    UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    UIView *fromView = fromVC.view;
    UIView *toView = toVC.view;
    
    UIView *containerView = transitionContext.containerView;
    NSTimeInterval duration = [self transitionDuration:transitionContext];
    
    // Hold refrence to transitionContext to notify it of completion
    self.transitionContext = transitionContext;
    
    // Create dynamic animator
    UIDynamicAnimator *animator = [[UIDynamicAnimator alloc]initWithReferenceView:containerView];
    animator.delegate = self;
    self.animator = animator;
    
    // Presenting Animation
    if (self.isAppearing)
    {
        fromView.userInteractionEnabled = NO;
        
        // Position toView  just above screen
        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;
        toView.frame = toViewInitialFrame;
        
        [containerView addSubview:toView];
        
        // Prevent rotation and adjust bounce
        UIDynamicItemBehavior *bodyBehavior = [[UIDynamicItemBehavior alloc]initWithItems:@[toView]];
        bodyBehavior.elasticity = 0.7;
        bodyBehavior.allowsRotation = NO;
        
        // Add gravity at exaggerated magnitude so animation doesn't seem slow
        UIGravityBehavior *gravityBehavior = [[UIGravityBehavior alloc]initWithItems:@[toView]];
        gravityBehavior.magnitude = 10.0f;
        
        // Set collision bounds to include off-screen view and have collision floor in center
        // where our final view should come to rest
        UICollisionBehavior *collisionBehavior = [[UICollisionBehavior alloc]initWithItems:@[toView]];
        UIEdgeInsets insets = UIEdgeInsetsMake(CGRectGetMinY(toViewInitialFrame), 0.0, CGRectGetHeight(fromViewInitialFrame) * 0.5 - CGRectGetHeight(toViewInitialFrame) * 0.5, 0.0);
        [collisionBehavior setTranslatesReferenceBoundsIntoBoundaryWithInsets:insets];
        self.collisionBehavior = collisionBehavior;
        
        // Keep track of finish time in case we need to end the animator befor the animator pauses
        self.finishTime = duration + self.animator.elapsedTime;
        
        // Closure that is called after every "tick" of the animator
        // Check if we exceed duration
        __weak ObjcDropOutAnimator *weakSelf = self;
        self.action = ^{
            __strong ObjcDropOutAnimator *strongSelf = weakSelf;
            if (strongSelf)
            {
                if (strongSelf.animator.elapsedTime >= strongSelf.finishTime)
                {
                    strongSelf.elapsedTimeExceededDuration = YES;
                    [strongSelf.animator removeBehavior:strongSelf];
                }
            }
        };
        
        // `DropOutAnimator` is a composit behavior, so add child behaviors to self
        [self addChildBehavior:collisionBehavior];
        [self addChildBehavior:bodyBehavior];
        [self addChildBehavior:gravityBehavior];
        
        // Add self to dynamic animator
        [self.animator addBehavior:self];
    }
    // Dismissing Animation
    else
    {
        // Allow rotation and have a elastic item
        UIDynamicItemBehavior *bodyBehavior = [[UIDynamicItemBehavior alloc] initWithItems:@[fromView]];
        bodyBehavior.elasticity = 0.8;
        bodyBehavior.angularResistance = 5.0;
        bodyBehavior.allowsRotation = YES;
        
        // Create gravity with exaggerated magnitude
        UIGravityBehavior *gravityBehavior = [[UIGravityBehavior alloc] initWithItems:@[fromView]];
        gravityBehavior.magnitude = 10.0f;
        
        // Collision boundary is set to have a floor just below the bottom of the screen
        UICollisionBehavior *collisionBehavior = [[UICollisionBehavior alloc] initWithItems:@[fromView]];
        UIEdgeInsets insets = UIEdgeInsetsMake(0, -1000, -225, -1000);
        [collisionBehavior setTranslatesReferenceBoundsIntoBoundaryWithInsets:insets];
        self.collisionBehavior = collisionBehavior;
        
        // Attachment behavior so view will have effect of hanging from a rope
        UIOffset offset = UIOffsetMake(70, -(CGRectGetHeight(fromView.bounds) / 2.0));
        
        CGPoint anchorPoint = CGPointMake(CGRectGetMaxX(fromView.bounds) - 40,
                                          CGRectGetMinY(fromView.bounds));
        anchorPoint = [containerView convertPoint:anchorPoint fromView:fromView];
        UIAttachmentBehavior *attachBehavior = [[UIAttachmentBehavior alloc] initWithItem:fromView offsetFromCenter:offset attachedToAnchor:anchorPoint];
        attachBehavior.frequency = 3.0;
        attachBehavior.damping = 0.3;
        attachBehavior.length = 40;
        self.attachBehavior = attachBehavior;
        
        // `DropOutAnimator` is a composit behavior, so add child behaviors to self
        [self addChildBehavior:collisionBehavior];
        [self addChildBehavior:bodyBehavior];
        [self addChildBehavior:gravityBehavior];
        [self addChildBehavior:attachBehavior];
        
        // Add self to dynamic animator
        [self.animator addBehavior:self];
        
        // Animation has two parts part one is hanging from rope.
        // Part two is bouncying off-screen
        // Divide duration in two
        self.finishTime = (2./3.) * duration + [self.animator elapsedTime];
        
        // After every "tick" of animator check if past time limit
        __weak ObjcDropOutAnimator *weakSelf = self;
        self.action = ^{
            __strong ObjcDropOutAnimator *strongSelf = weakSelf;
            if (strongSelf)
            {
                if ([strongSelf.animator elapsedTime] >= strongSelf.finishTime)
                {
                    strongSelf.elapsedTimeExceededDuration = YES;
                    [strongSelf.animator removeBehavior:strongSelf];
                }
            }
        };
    }
}

- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext
{
    return self.duration;
}

- (void)dynamicAnimatorDidPause:(UIDynamicAnimator *)animator
{
    // Animator has reached stasis
    if (self.isAppearing)
    {
        // Check if we are out of time
        if (self.elapsedTimeExceededDuration)
        {
            // Move to final positions
            UIView *toView = [self.transitionContext viewControllerForKey:UITransitionContextToViewControllerKey].view;
            UIView *containerView = [self.transitionContext containerView];
            toView.center = containerView.center;
            self.elapsedTimeExceededDuration = NO;
        }
        
        // Clean up and call completion
        [self.transitionContext completeTransition:![self.transitionContext transitionWasCancelled]];
        for (UIDynamicBehavior *behavior in self.childBehaviors)
        {
            [self removeChildBehavior:behavior];
        }
        [animator removeAllBehaviors];
        self.transitionContext = nil;
    }
    // Dismissing
    else
    {
        if (self.attachBehavior)
        {
            // If we have an attachment, we are at the end of part one and start part two.
            [self removeChildBehavior:self.attachBehavior];
            self.attachBehavior = nil;
            [animator addBehavior:self];
            NSTimeInterval duration = [self transitionDuration:self.transitionContext];
            self.finishTime = 1./3. * duration + [animator elapsedTime];
        }
        else
        {
            // Clean up and call completion
            UIView *fromView = [self.transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey].view;
            UIView *toView = [self.transitionContext viewControllerForKey:UITransitionContextToViewControllerKey].view;
            [fromView removeFromSuperview];
            toView.userInteractionEnabled = YES;
            
            [self.transitionContext completeTransition:![self.transitionContext transitionWasCancelled]];
            for (UIDynamicBehavior *behavior in self.childBehaviors)
            {
                [self removeChildBehavior:behavior];
            }
            [animator removeAllBehaviors];
            self.transitionContext = nil;
        }
    }
}

Som sammansatt beteende kan DropOutAnimator kombinera ett antal olika beteenden för att utföra sina presenterande och avvisande animationer. DropOutAnimator visar också hur man använder action blocket ett beteende för att inspektera de platser där de objekt samt den tid som förflutit en teknik som kan användas för att avlägsna vyer som rör sig utanför skärmen eller Trunkera animationer som ännu inte nå stasis.

För mer information 2013 WWDC-sessionen "Avancerade tekniker med UIKit Dynamics" samt SOLPresentingFun

Skuggövergång med fysik i verkligheten med hjälp av UIDynamicBehaviors

Detta exempel visar hur man gör en interaktiv presentationsövergång med "verklig" fysik som liknar iOS: s aviseringskärm.

Till att börja med behöver vi en presentationsvisningskontroll som skuggan kommer att visas över. Den här visningskontrollern fungerar också som vår UIViewControllerTransitioningDelegate för vår presenterade view controller och kommer att sälja animatörer för vår övergång. Så vi skapar instanser av våra interaktiva animatörer (en för att presentera, en för att avslå). Vi skapar också en instans av skuggavyregulatorn, som i detta exempel bara är en visningskontroller med en etikett. Eftersom vi vill att samma pan-gest ska driva hela interaktionen överför vi referenser till den nuvarande visningskontrollern och skuggan till våra interaktiva animatörer.

Snabb

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

Vi vill egentligen bara någonsin vilja presentera vår nyans genom en interaktiv övergång men på grund av hur UIViewControllerTransitioningDelegate fungerar om vi inte returnerar en vanlig animationskontroll kommer vår interaktiva styrenhet aldrig att användas. Därför skapar vi en EmptyAnimator klass som överensstämmer med UIViewControllerAnimatedTransitioning .

Snabb

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

Slutligen måste vi faktiskt skapa ShadeAnimator som är en underklass av UIDynamicBehavior som överensstämmer med UIViewControllerInteractiveTransitioning .

Snabb

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

Animatorn utlöser början av övergången när pan-gesten börjar. Och flyttar helt enkelt vyn när gesten ändras. Men när gesten slutar är det när UIDynamicBehaviors avgör om övergången ska slutföras eller avbrytas. För att göra det använder den en bilaga och kollisionsbeteende. För mer information se WWDC-sessionen 2013 "Avancerade tekniker med UIKit Dynamics .

Kartdynamiska animationspositioner ändras till gränser

Detta exempel visar hur du anpassar UIDynamicItem protokollet för att kartlägga positionsändringar i en vy som dynamiskt animeras till gränsvärden för att skapa en UIButton som expanderar och kontrakterar på ett elastiskt sätt.

Till att börja måste vi skapa ett nytt protokoll som redskap UIDynamicItem men det har också en inställbar och gettable bounds egendom.

Snabb

protocol ResizableDynamicItem: UIDynamicItem
{
    var bounds: CGRect { set get }
}
extension UIView: ResizableDynamicItem {}

Objective-C

@protocol ResizableDynamicItem <UIDynamicItem>
@property (nonatomic, readwrite) CGRect bounds;
@end

Vi skapar sedan ett omslagobjekt som kommer att linda in ett UIDynamicItem men kartlägger UIDynamicItem till objektets bredd och höjd. Vi kommer också att erbjuda genomsträckningar för bounds och transform av den underliggande artikeln. Detta kommer att orsaka eventuella förändringar som den dynamiska animatorn gör i mitten x och y-värdena för det underliggande objektet kommer att tillämpas på objekten bredd och höjd.

Snabb

final class PositionToBoundsMapping: NSObject, UIDynamicItem
{
    var target: ResizableDynamicItem
    
    init(target: ResizableDynamicItem)
    {
        self.target = target
        super.init()
    }
    
    var bounds: CGRect
    {
        get
        {
            return self.target.bounds
        }
    }
    
    var center: CGPoint
    {
        get
        {
            return CGPoint(x: self.target.bounds.width, y: self.target.bounds.height)
        }
        
        set
        {
            self.target.bounds = CGRect(x: 0.0, y: 0.0, width: newValue.x, height: newValue.y)
        }
    }
    
    var transform: CGAffineTransform
    {
        get
        {
            return self.target.transform
        }
        
        set
        {
            self.target.transform = newValue
        }
    }
}

Objective-C

@interface PositionToBoundsMapping ()
@property (nonatomic, strong) id<ResizableDynamicItem> target;
@end

@implementation PositionToBoundsMapping

- (instancetype)initWithTarget:(id<ResizableDynamicItem>)target
{
    self = [super init];
    if (self)
    {
        _target = target;
    }
    return self;
}

- (CGRect)bounds
{
    return self.target.bounds;
}

- (CGPoint)center
{
    return CGPointMake(self.target.bounds.size.width, self.target.bounds.size.height);
}

- (void)setCenter:(CGPoint)center
{
    self.target.bounds = CGRectMake(0, 0, center.x, center.y);
}

- (CGAffineTransform)transform
{
    return self.target.transform;
}

- (void)setTransform:(CGAffineTransform)transform
{
    self.target.transform = transform;
}

@end

Slutligen skapar vi en UIViewController som har en knapp. När knappen trycks in skapar vi PositionToBoundsMapping med knappen som det inslagna dynamiska objektet. Vi skapar en UIAttachmentBehavior till sin nuvarande position och lägger sedan till en omedelbar UIPushBehavior till den. Men eftersom vi har kartlagt ändrar dess gränser, rör sig inte knappen utan växer och krymper.

Snabb

final class ViewController: UIViewController
{
    lazy var button: UIButton =
    {
        let button = UIButton(frame: CGRect(x: 0.0, y: 0.0, width: 300.0, height: 200.0))
        button.backgroundColor = .red
        button.layer.cornerRadius = 15.0
        button.setTitle("Tap Me", for: .normal)
        self.view.addSubview(button)
        return button
    }()
    
    var buttonBounds = CGRect.zero
    var animator: UIDynamicAnimator?
    
    override func viewDidLoad() 
    {
        super.viewDidLoad()
        view.backgroundColor = .white
        button.addTarget(self, action: #selector(self.didPressButton(sender:)), for: .touchUpInside)
        buttonBounds = button.bounds
    }
    
    override func viewDidLayoutSubviews() 
    {
        super.viewDidLayoutSubviews()
        button.center = view.center
    }
    
    func didPressButton(sender: UIButton)
    {
        // Reset bounds so if button is press twice in a row, previous changes don't propogate
        button.bounds = buttonBounds
        let animator = UIDynamicAnimator(referenceView: view)
        
        // Create mapping
        let buttonBoundsDynamicItem = PositionToBoundsMapping(target: button)
        
        // Add Attachment behavior
        let attachmentBehavior = UIAttachmentBehavior(item: buttonBoundsDynamicItem, attachedToAnchor: buttonBoundsDynamicItem.center)
        
        // Higher frequency faster oscillation
        attachmentBehavior.frequency = 2.0
        
        // Lower damping longer oscillation lasts
        attachmentBehavior.damping = 0.1
        animator.addBehavior(attachmentBehavior)
        
        let pushBehavior = UIPushBehavior(items: [buttonBoundsDynamicItem], mode: .instantaneous)
        
        // Change angle to determine how much height/ width should change 45° means heigh:width is 1:1
        pushBehavior.angle = .pi / 4.0
        
        // Larger magnitude means bigger change
        pushBehavior.magnitude = 30.0
        animator.addBehavior(pushBehavior)
        pushBehavior.active = true
        
        // Hold refrence so animator is not released
        self.animator = animator
    }
}

Objective-C

@interface ViewController ()
@property (nonatomic, strong) UIButton *button;
@property (nonatomic, assign) CGRect buttonBounds;
@property (nonatomic, strong) UIDynamicAnimator *animator;
@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor whiteColor];
    [self.button addTarget:self action:@selector(didTapButton:) forControlEvents:UIControlEventTouchUpInside];
    self.buttonBounds = self.button.bounds;
}

- (void)viewDidLayoutSubviews
{
    [super viewDidLayoutSubviews];
    self.button.center = self.view.center;
}

- (UIButton *)button
{
    if (!_button)
    {
        _button = [[UIButton alloc]initWithFrame:CGRectMake(0.0, 0.0, 200.0, 200.0)];
        _button.backgroundColor = [UIColor redColor];
        _button.layer.cornerRadius = 15.0;
        [_button setTitle:@"Tap Me" forState:UIControlStateNormal];
        [self.view addSubview:_button];
    }
    return _button;
}

- (void)didTapButton:(id)sender
{
    self.button.bounds = self.buttonBounds;
    UIDynamicAnimator *animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];
    PositionToBoundsMapping *buttonBoundsDynamicItem = [[PositionToBoundsMapping alloc]initWithTarget:sender];
    UIAttachmentBehavior *attachmentBehavior = [[UIAttachmentBehavior alloc]initWithItem:buttonBoundsDynamicItem attachedToAnchor:buttonBoundsDynamicItem.center];
    [attachmentBehavior setFrequency:2.0];
    [attachmentBehavior setDamping:0.3];
    [animator addBehavior:attachmentBehavior];
    
    UIPushBehavior *pushBehavior = [[UIPushBehavior alloc] initWithItems:@[buttonBoundsDynamicItem] mode:UIPushBehaviorModeInstantaneous];
    pushBehavior.angle = M_PI_4;
    pushBehavior.magnitude = 2.0;
    [animator addBehavior:pushBehavior];
    
    [pushBehavior setActive:TRUE];
    
    self.animator = animator;
}

@end

Mer information finns i UIKit Dynamics Catalog