iOS
UIKit Dynamics met UICollectionView

Invoering

Een aangepast sleepgedrag maken met UIDynamicAnimator

Dit voorbeeld laat zien hoe u een aangepast UIDynamicBehavior kunt maken door UIDynamicBehavior subklasse te UICollectionViewFlowLayout en UICollectionViewFlowLayout subklasse te UICollectionViewFlowLayout . In het voorbeeld hebben we UICollectionView waarmee u meerdere items kunt selecteren. Vervolgens kunnen deze items met een lang UIDynamicAnimator worden gesleept in een elastische, "verende" animatie aangedreven door een UIDynamicAnimator .

Het UIAttachmentBehavior wordt geproduceerd door een gedrag op laag niveau te combineren dat een UIAttachmentBehavior aan de hoeken van een UIDynamicItem en een gedrag op hoog niveau dat het gedrag op laag niveau beheert voor een aantal UIDynamicItems .

We kunnen beginnen met het creëren van dit gedrag op laag niveau, we noemen RectangleAttachmentBehavior

Snel

final class RectangleAttachmentBehavior: UIDynamicBehavior
{
    init(item: UIDynamicItem, point: CGPoint)
    {
        // Higher frequency more "ridged" formation
        let frequency: CGFloat = 8.0
        
        // Lower damping longer animation takes to come to rest
        let damping: CGFloat = 0.6
        
        super.init()
        
        // Attachment points are four corners of item
        let points = self.attachmentPoints(for: point)
        
        let attachmentBehaviors: [UIAttachmentBehavior] = points.map
        {
            let attachmentBehavior = UIAttachmentBehavior(item: item, attachedToAnchor: $0)
            attachmentBehavior.frequency = frequency
            attachmentBehavior.damping = damping
            return attachmentBehavior
        }
        
        attachmentBehaviors.forEach
        {
            addChildBehavior($0)
        }
    }
    
    func updateAttachmentLocation(with point: CGPoint)
    {
        // Update anchor points to new attachment points
        let points = self.attachmentPoints(for: point)
        let attachments = self.childBehaviors.flatMap { $0 as? UIAttachmentBehavior }
        let pairs = zip(points, attachments)
        pairs.forEach { $0.1.anchorPoint = $0.0 }
    }
    
    func attachmentPoints(for point: CGPoint) -> [CGPoint]
    {
        // Width and height should be close to the width and height of the item
        let width: CGFloat = 40.0
        let height: CGFloat = 40.0
        
        let topLeft = CGPoint(x: point.x - width * 0.5, y: point.y - height * 0.5)
        let topRight = CGPoint(x: point.x + width * 0.5, y: point.y - height * 0.5)
        let bottomLeft = CGPoint(x: point.x - width * 0.5, y: point.y + height * 0.5)
        let bottomRight = CGPoint(x: point.x + width * 0.5, y: point.y + height * 0.5)
        let points = [topLeft, topRight, bottomLeft, bottomRight]
        return points
    }
}

Doelstelling C

@implementation RectangleAttachmentBehavior

- (instancetype)initWithItem:(id<UIDynamicItem>)item point:(CGPoint)point
{
    CGFloat frequency = 8.0f;
    CGFloat damping = 0.6f;
    self = [super init];
    if (self)
    {
        NSArray <NSValue *> *pointValues = [self attachmentPointValuesForPoint:point];
        for (NSValue *value in pointValues)
        {
            UIAttachmentBehavior *attachment = [[UIAttachmentBehavior alloc]initWithItem:item attachedToAnchor:[value CGPointValue]];
            attachment.frequency = frequency;
            attachment.damping = damping;
            [self addChildBehavior:attachment];
        }
    }
    return self;
}

- (void)updateAttachmentLocationWithPoint:(CGPoint)point
{
    NSArray <NSValue *> *pointValues = [self attachmentPointValuesForPoint:point];
    for (NSInteger i = 0; i < pointValues.count; i++)
    {
        NSValue *pointValue = pointValues[i];
        UIAttachmentBehavior *attachment = self.childBehaviors[i];
        attachment.anchorPoint = [pointValue CGPointValue];
    }
}

- (NSArray <NSValue *> *)attachmentPointValuesForPoint:(CGPoint)point
{
    CGFloat width = 40.0f;
    CGFloat height = 40.0f;
    
    CGPoint topLeft = CGPointMake(point.x - width * 0.5, point.y - height * 0.5);
    CGPoint topRight = CGPointMake(point.x + width * 0.5, point.y - height * 0.5);
    CGPoint bottomLeft = CGPointMake(point.x - width * 0.5, point.y + height * 0.5);
    CGPoint bottomRight = CGPointMake(point.x + width * 0.5, point.y + height * 0.5);
    
    NSArray <NSValue *> *pointValues = @[[NSValue valueWithCGPoint:topLeft], [NSValue valueWithCGPoint:topRight], [NSValue valueWithCGPoint:bottomLeft], [NSValue valueWithCGPoint:bottomRight]];
    return pointValues;
}

@end

Vervolgens kunnen we het gedrag op hoog niveau creëren dat een aantal RectangleAttachmentBehavior combineert.

Snel

final class DragBehavior: UIDynamicBehavior
{
    init(items: [UIDynamicItem], point: CGPoint)
    {
        super.init()
        items.forEach
        {
            let rectAttachment = RectangleAttachmentBehavior(item: $0, point: point)
            self.addChildBehavior(rectAttachment)
        }
    }
    
    func updateDragLocation(with point: CGPoint)
    {
        // Tell low-level behaviors location has changed
        self.childBehaviors.flatMap { $0 as? RectangleAttachmentBehavior }.forEach { $0.updateAttachmentLocation(with: point) }
    }
}

Doelstelling C

@implementation DragBehavior

- (instancetype)initWithItems:(NSArray <id<UIDynamicItem>> *)items point: (CGPoint)point
{
    self = [super init];
    if (self)
    {
        for (id<UIDynamicItem> item in items)
        {
            RectangleAttachmentBehavior *rectAttachment = [[RectangleAttachmentBehavior alloc]initWithItem:item point:point];
            [self addChildBehavior:rectAttachment];
        }
    }
    return self;
}

- (void)updateDragLocationWithPoint:(CGPoint)point
{
    for (RectangleAttachmentBehavior *rectAttachment in self.childBehaviors)
    {
        [rectAttachment updateAttachmentLocationWithPoint:point];
    }
}

@end

Nu ons gedrag op zijn plaats is, is de volgende stap om ze aan ons collectieoverzicht toe te voegen wanneer. Omdat we normaal gesproken een standaard rasterlay-out willen, kunnen we UICollectionViewFlowLayout en alleen attributen wijzigen tijdens het slepen. We doen dit voornamelijk door de dwingende layoutAttributesForElementsInRect en het gebruik van de UIDynamicAnimator's itemsInRect .

Snel

final class DraggableLayout: UICollectionViewFlowLayout
{
    // Array that holds dragged index paths
    var indexPathsForDraggingElements: [IndexPath]?
    
    // The dynamic animator that will animate drag behavior
    var animator: UIDynamicAnimator?
    
    // Custom high-level behavior that dictates drag animation
    var dragBehavior: DragBehavior?
    
    // Where dragging starts so can return there once dragging ends
    var startDragPoint = CGPoint.zero
    
    // Bool to keep track if dragging has ended
    var isFinishedDragging = false
    
    
    // Method to inform layout that dragging has started
    func startDragging(indexPaths selectedIndexPaths: [IndexPath], from point: CGPoint)
    {
        indexPathsForDraggingElements = selectedIndexPaths
        animator = UIDynamicAnimator(collectionViewLayout: self)
        animator?.delegate = self
        
        // Get all of the draggable attributes but change zIndex so above other cells
        let draggableAttributes: [UICollectionViewLayoutAttributes] = selectedIndexPaths.flatMap {
            let attribute = super.layoutAttributesForItem(at: $0)
            attribute?.zIndex = 1
            return attribute
        }
        
        startDragPoint = point
        
        // Add them to high-level behavior
        dragBehavior = DragBehavior(items: draggableAttributes, point: point)
        
        // Add high-level behavior to animator
        animator?.addBehavior(dragBehavior!)
    }
    
    func updateDragLocation(_ point: CGPoint)
    {
        // Tell high-level behavior that point has updated
        dragBehavior?.updateDragLocation(with: point)
    }
    
    func endDragging()
    {
        isFinishedDragging = true
        
        // Return high-level behavior to starting point
        dragBehavior?.updateDragLocation(with: startDragPoint)
    }
    
    func clearDraggedIndexPaths()
    {
        // Reset state for next drag event
        animator = nil
        indexPathsForDraggingElements = nil
        isFinishedDragging = false
    }
    
    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]?
    {
        let existingAttributes: [UICollectionViewLayoutAttributes] = super.layoutAttributesForElements(in: rect) ?? []
        var allAttributes = [UICollectionViewLayoutAttributes]()
        
        // Get normal flow layout attributes for non-drag items
        for attributes in existingAttributes
        {
            if (indexPathsForDraggingElements?.contains(attributes.indexPath) ?? false) == false
            {
                allAttributes.append(attributes)
            }
        }
        
        // Add dragged item attributes by asking animator for them
        if let animator = self.animator
        {
            let animatorAttributes: [UICollectionViewLayoutAttributes] = animator.items(in: rect).flatMap { $0 as? UICollectionViewLayoutAttributes }
            allAttributes.append(contentsOf: animatorAttributes)
        }
        return allAttributes
    }
}
extension DraggableLayout: UIDynamicAnimatorDelegate
{
    func dynamicAnimatorDidPause(_ animator: UIDynamicAnimator)
    {
        // Animator has paused and done dragging; reset state
        guard isFinishedDragging else { return }
        clearDraggedIndexPaths()
    }
}

Doelstelling C

@interface DraggableLayout () <UIDynamicAnimatorDelegate>
@property (nonatomic, strong) NSArray <NSIndexPath *> *indexPathsForDraggingElements;
@property (nonatomic, strong) UIDynamicAnimator *animator;
@property (nonatomic, assign) CGPoint startDragPoint;
@property (nonatomic, assign) BOOL finishedDragging;
@property (nonatomic, strong) DragBehavior *dragBehavior;
@end

@implementation DraggableLayout

- (void)startDraggingWithIndexPaths:(NSArray <NSIndexPath *> *)selectedIndexPaths fromPoint:(CGPoint)point
{
    self.indexPathsForDraggingElements = selectedIndexPaths;
    self.animator = [[UIDynamicAnimator alloc]initWithCollectionViewLayout:self];
    self.animator.delegate = self;
    NSMutableArray *draggableAttributes = [[NSMutableArray alloc]initWithCapacity:selectedIndexPaths.count];
    for (NSIndexPath *indexPath in selectedIndexPaths)
    {
        UICollectionViewLayoutAttributes *attributes = [super layoutAttributesForItemAtIndexPath:indexPath];
        attributes.zIndex = 1;
        [draggableAttributes addObject:attributes];
    }
    self.startDragPoint = point;
    self.dragBehavior = [[DragBehavior alloc]initWithItems:draggableAttributes point:point];
    [self.animator addBehavior:self.dragBehavior];
}

- (void)updateDragLoactionWithPoint:(CGPoint)point
{
    [self.dragBehavior updateDragLocationWithPoint:point];
}

- (void)endDragging
{
    self.finishedDragging = YES;
    [self.dragBehavior updateDragLocationWithPoint:self.startDragPoint];
}

- (void)clearDraggedIndexPath
{
    self.animator = nil;
    self.indexPathsForDraggingElements = nil;
    self.finishedDragging = NO;
}

- (void)dynamicAnimatorDidPause:(UIDynamicAnimator *)animator
{
    if (self.finishedDragging)
    {
        [self clearDraggedIndexPath];
    }
}

- (NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect
{
    NSArray *existingAttributes = [super layoutAttributesForElementsInRect:rect];
    NSMutableArray *allAttributes = [[NSMutableArray alloc]initWithCapacity:existingAttributes.count];
    for (UICollectionViewLayoutAttributes *attributes in existingAttributes)
    {
        if (![self.indexPathsForDraggingElements containsObject:attributes.indexPath])
        {
            [allAttributes addObject:attributes];
        }
    }
    [allAttributes addObjectsFromArray:[self.animator itemsInRect:rect]];
    return allAttributes;
}

@end

Ten slotte maken we een UICollectionView die onze UICollectionView en ons lange- UICollectionView afhandelt.

Snel

final class ViewController: UIViewController
{
    // Collection view that displays cells
    lazy var collectionView: UICollectionView =
    {
        let collectionView = UICollectionView(frame: .zero, collectionViewLayout: DraggableLayout())
        collectionView.backgroundColor = .white
        collectionView.translatesAutoresizingMaskIntoConstraints = false
        self.view.addSubview(collectionView)
        collectionView.topAnchor.constraint(equalTo: self.topLayoutGuide.bottomAnchor).isActive = true
        collectionView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor).isActive = true
        collectionView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor).isActive = true
        collectionView.bottomAnchor.constraint(equalTo: self.bottomLayoutGuide.topAnchor).isActive = true
        
        return collectionView
    }()
    
    // Gesture that drives dragging
    lazy var longPress: UILongPressGestureRecognizer =
    {
        let longPress = UILongPressGestureRecognizer(target: self, action: #selector(self.handleLongPress(sender:)))
        return longPress
    }()
    
    // Array that holds selected index paths
    var selectedIndexPaths = [IndexPath]()
    
    override func viewDidLoad()
    {
        super.viewDidLoad()
        collectionView.delegate = self
        collectionView.dataSource = self
        collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")
        collectionView.addGestureRecognizer(longPress)
    }
    
    func handleLongPress(sender: UILongPressGestureRecognizer)
    {
        guard let draggableLayout = collectionView.collectionViewLayout as? DraggableLayout else { return }
        let location = sender.location(in: collectionView)
        switch sender.state
        {
        case .began:
            draggableLayout.startDragging(indexPaths: selectedIndexPaths, from: location)
        case .changed:
            draggableLayout.updateDragLocation(location)
        case .ended, .failed, .cancelled:
            draggableLayout.endDragging()
        case .possible:
            break
        }
    }
}
extension ViewController: UICollectionViewDelegate, UICollectionViewDataSource
{
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
    {
        return 1000
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
    {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath)
        cell.backgroundColor = .gray
        if selectedIndexPaths.contains(indexPath) == true
        {
            cell.backgroundColor = .red
        }
        return cell
    }
    
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath)
    {
        // Bool that determines if cell is being selected or unselected
        let isSelected = !selectedIndexPaths.contains(indexPath)
        let cell = collectionView.cellForItem(at: indexPath)
        cell?.backgroundColor = isSelected ? .red : .gray
        if isSelected
        {
            selectedIndexPaths.append(indexPath)
        }
        else
        {
            selectedIndexPaths.remove(at: selectedIndexPaths.index(of: indexPath)!)
        }
    }
}

Doelstelling C

@interface ViewController () <UICollectionViewDelegate, UICollectionViewDataSource>
@property (nonatomic, strong) UICollectionView *collectionView;
@property (nonatomic, strong) UILongPressGestureRecognizer *longPress;
@property (nonatomic, strong) NSMutableArray <NSIndexPath *> *selectedIndexPaths;
@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.collectionView.delegate = self;
    self.collectionView.dataSource = self;
    [self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"Cell"];
    [self.collectionView addGestureRecognizer:self.longPress];
    self.selectedIndexPaths = [[NSMutableArray alloc]init];
}

- (UICollectionView *)collectionView
{
    if (!_collectionView)
    {
        _collectionView = [[UICollectionView alloc]initWithFrame:CGRectZero collectionViewLayout:[[DraggableLayout alloc]init]];
        _collectionView.backgroundColor = [UIColor whiteColor];
        _collectionView.translatesAutoresizingMaskIntoConstraints = NO;
        [self.view addSubview:_collectionView];
        [_collectionView.topAnchor constraintEqualToAnchor:self.topLayoutGuide.bottomAnchor].active = YES;
        [_collectionView.leadingAnchor constraintEqualToAnchor:self.view.leadingAnchor].active = YES;
        [_collectionView.trailingAnchor constraintEqualToAnchor:self.view.trailingAnchor].active = YES;
        [_collectionView.bottomAnchor constraintEqualToAnchor:self.bottomLayoutGuide.topAnchor].active = YES;
    }
    return _collectionView;
}

- (UILongPressGestureRecognizer *)longPress
{
    if (!_longPress)
    {
        _longPress = [[UILongPressGestureRecognizer alloc]initWithTarget:self action:@selector(handleLongPress:)];
    }
    return _longPress;
}

- (void)handleLongPress:(UILongPressGestureRecognizer *)sender
{
    DraggableLayout *draggableLayout = (DraggableLayout *)self.collectionView.collectionViewLayout;
    CGPoint location = [sender locationInView:self.collectionView];
    if (sender.state == UIGestureRecognizerStateBegan)
    {
        [draggableLayout startDraggingWithIndexPaths:self.selectedIndexPaths fromPoint:location];
    }
    else if(sender.state == UIGestureRecognizerStateChanged)
    {
        [draggableLayout updateDragLoactionWithPoint:location];
    }
    else if(sender.state == UIGestureRecognizerStateEnded ||  sender.state == UIGestureRecognizerStateCancelled || sender.state == UIGestureRecognizerStateFailed)
    {
        [draggableLayout endDragging];
    }
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return 1000;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
    cell.backgroundColor = [UIColor grayColor];
    if ([self.selectedIndexPaths containsObject:indexPath])
    {
        cell.backgroundColor = [UIColor redColor];
    }
    return cell;
}

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    BOOL isSelected = ![self.selectedIndexPaths containsObject:indexPath];
    UICollectionViewCell *cell = [collectionView cellForItemAtIndexPath:indexPath];
    if (isSelected)
    {
        cell.backgroundColor = [UIColor redColor];
        [self.selectedIndexPaths addObject:indexPath];
    }
    else
    {
        cell.backgroundColor = [UIColor grayColor];
        [self.selectedIndexPaths removeObject:indexPath];
    }
}

@end

Voor meer informatie 2013 WWDC-sessie "Geavanceerde technieken met UIKit Dynamics"