iOS
UICollectionView के साथ UIKit डायनामिक्स

परिचय

UIDynamicAnimator के साथ एक कस्टम ड्रैगिंग व्यवहार बनाना

यह उदाहरण दिखाता है कि UIDynamicBehavior द्वारा कस्टम ड्रैगिंग व्यवहार कैसे बनाया UIDynamicBehavior और UIDynamicBehavior को उप- UICollectionViewFlowLayout । उदाहरण में, हमारे पास UICollectionView जो कई वस्तुओं के चयन की अनुमति देता है। फिर एक लंबे प्रेस के इशारे के साथ उन वस्तुओं को एक लोचदार, "स्प्रिंगली" एनीमेशन में खींचा जा सकता है, जिसे एक UIDynamicAnimator द्वारा संचालित किया गया है।

खींच व्यवहार एक निम्न स्तर के व्यवहार है कि एक कहते हैं के संयोजन द्वारा निर्मित है UIAttachmentBehavior एक के कोनों के लिए करने के लिए UIDynamicItem और एक उच्च स्तरीय व्यवहार है कि के एक नंबर के लिए निम्न स्तर के व्यवहार का प्रबंधन करता है UIDynamicItems ।

हम इस निम्न-स्तरीय व्यवहार को बनाकर शुरू कर सकते हैं, हम RectangleAttachmentBehavior कॉल करेंगे

तीव्र

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
    }
}

उद्देश्य सी

@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

अगला हम उच्च-स्तरीय व्यवहार बना सकते हैं जो कई RectangleAttachmentBehavior को जोड़ देगा।

तीव्र

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) }
    }
}

उद्देश्य सी

@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

अब हमारे व्यवहार के साथ, अगला कदम उन्हें हमारे संग्रह दृश्य में जोड़ना है जब। क्योंकि आम तौर पर हम एक मानक ग्रिड लेआउट चाहते हैं, हम UICollectionViewFlowLayout को उप-वर्ग कर सकते हैं और खींचते समय केवल विशेषताओं को बदल सकते हैं। हम इसे मुख्य रूप से layoutAttributesForElementsInRect माध्यम से करते हैं layoutAttributesForElementsInRect को ओवरराइड कर रहे हैं और UIDynamicAnimator's सुविधा विधि itemsInRect UIDynamicAnimator's उपयोग कर itemsInRect ।

तीव्र

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()
    }
}

उद्देश्य सी

@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

अंत में, हम एक व्यू कंट्रोलर बनाएंगे जो हमारा UICollectionView और हमारे लॉन्ग प्रेस जेस्चर को हैंडल करेगा।

तीव्र

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)!)
        }
    }
}

उद्देश्य सी

@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

अधिक जानकारी के लिए 2013 WWDC सत्र "उन्नत तकनीकों के साथ UIKit गतिशीलता"