在 CollectionView 上滑动删除

Question

我正在尝试复制 iOS 的滑动删除功能。我知道它可以立即在 tableview 上使用，但是我需要构建的 UI 从 Collection View 中受益。因此，我需要一个自定义实现，我将使用向上滑动手势。幸运的是，这是我自己设法实现的，但是我很难弄清楚我需要如何设置滑动删除/点击删除/忽略功能。

用户界面当前如下所示：

所以我正在使用以下集合视图：

func buildCollectionView() {
    let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
    layout.scrollDirection = .horizontal
    layout.minimumInteritemSpacing = 0;
    layout.minimumLineSpacing = 4;

    collectionView = UICollectionView(frame: CGRect(x: 0, y: screenSize.midY - 120, width: screenSize.width, height: 180), collectionViewLayout: layout)

    collectionView.dataSource = self
    collectionView.delegate = self
    collectionView.register(VideoCell.self, forCellWithReuseIdentifier: "videoCell")
    collectionView.showsHorizontalScrollIndicator = false
    collectionView.showsVerticalScrollIndicator = false
    collectionView.contentInset = UIEdgeInsetsMake(0, 20, 0, 30)
    collectionView.backgroundColor = UIColor.white()
    collectionView.alpha = 0.0


    //can swipe cells outside collectionview region
    collectionView.layer.masksToBounds = false


    swipeUpRecognizer = UIPanGestureRecognizer(target: self, action: #selector(self.deleteCell))
    swipeUpRecognizer.delegate = self

    collectionView.addGestureRecognizer(swipeUpRecognizer)
    collectionView.isUserInteractionEnabled = true
}

我的自定义视频单元包含一个图像，其下方是删除按钮。因此，如果您向上滑动图像，则会弹出删除按钮。不确定这是否是正确的方法：

class VideoCell : UICollectionViewCell {
var deleteView: UIButton!
var imageView: UIImageView!

override init(frame: CGRect) {
    super.init(frame: frame)

    deleteView = UIButton(frame: CGRect(x: 0, y: 0, width: frame.size.width, height: frame.size.height))
    deleteView.contentMode = UIViewContentMode.scaleAspectFit
    contentView.addSubview(deleteView)

    imageView = UIImageView(frame: CGRect(x: 0, y: 0, width: frame.size.width, height: frame.size.height))
    imageView.contentMode = UIViewContentMode.scaleAspectFit
    contentView.addSubview(imageView)


}

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}
}

我正在使用以下逻辑：

func deleteCell(sender: UIPanGestureRecognizer) {
    let tapLocation = sender.location(in: self.collectionView)
    let indexPath = self.collectionView.indexPathForItem(at: tapLocation)

    if velocity.y < 0 { 
        //detect if there is a swipe up and detect it's distance. If the distance is far enough we snap the cells Imageview to the top otherwise we drop it back down. This works fine already.
    }
}

但问题从这里开始。一旦我的单元格超出 collectionview 边界，我就无法再访问它了。我仍然想进一步滑动它以将其删除。我只能通过滑动删除按钮来做到这一点，但我希望它上面的 Imageview 也可以滑动。或者，如果我点击 collectionview 之外的图像，它应该滑回该行而不是删除它。

如果我增加 collectionview 边界，我可以防止这个问题，但我也可以滑动以移除单元格的可见高度之外。这是由 collectionview 中的 tapLocation 引起的，它检测到 indexPath。我不想要的东西。我希望向上滑动只适用于 collectionview 的单元格。

按钮和图像也会相互干扰，因为我无法区分它们。它们都在同一个单元格中，这就是为什么我想知道是否应该在单元格中设置删除按钮。或者我应该把它放在哪里？我还可以用它制作两个按钮并根据状态禁用用户交互，但不确定最终会如何。

Answer 1

因此，如果您希望滑动手势识别器在其位于集合视图之外时继续记录移动，则需要将其附加到集合视图的父级，因此它会限制在用户可以滑动的整个区域.

这确实意味着您会在集合视图之外获得滑动，但您可以很容易地忽略使用任意数量的技术的那些。

要注册删除按钮点击，您需要在按钮上调用 addTarget:action:forControlEvents:

我会将单元格保持原样，将图像和按钮放在一起。这将更容易管理，并且它们属于一起。

要管理上下移动图像，我会考虑使用变换或 NSLayoutConstraint。然后，您只需调整一个值，使其与用户滑动同步上下移动。不要乱用框架。

Answer 2

出于我自己的好奇心，我尝试复制您正在尝试做的事情，并让它以某种方式运作良好。它与您设置滑动手势的方式不同，因为我没有使用平移，但您说您已经拥有该部分，并且没有花费太多时间。 Pan 显然是让它交互的更可靠的解决方案，但计算时间更长，但它的效果和处理应该与我的示例相差不大。

为了解决无法在单元格外滑动的问题，我决定检查该点是否在滑动矩形中，这是非滑动矩形高度的两倍，如下所示：

            let cellFrame = activeCell.frame
            let rect = CGRectMake(cellFrame.origin.x, cellFrame.origin.y - cellFrame.height, cellFrame.width, cellFrame.height*2)
            if CGRectContainsPoint(rect, point) {
                // If swipe point is in the cell delete it

                let indexPath = myView.indexPathForCell(activeCell)
                cats.removeAtIndex(indexPath!.row)
                myView.deleteItemsAtIndexPaths([indexPath!])

            }

我用 cmets 创建了一个演示：https://github.com/imbue11235/swipeToDeleteCell

无论如何，我希望它对您有所帮助！

Answer 3

如果你想让它变得通用：

制作服装可滑动视图：

import UIKit

class SwipeView: UIView {
lazy var label: UILabel = {
    let label = UILabel()
    label.textColor = .black
    label.backgroundColor = .green
    return label
}()

let visableView = UIView()
var originalPoint: CGPoint!
var maxSwipe: CGFloat! = 50 {
    didSet(newValue) {
        maxSwipe = newValue
    }
}

@IBInspectable var swipeBufffer: CGFloat = 2.0
@IBInspectable var highVelocity: CGFloat = 300.0

private let originalXCenter: CGFloat = UIScreen.main.bounds.width / 2
private var panGesture: UIPanGestureRecognizer!

public var isPanGestureEnabled: Bool {
    get { return panGesture.isEnabled }
    set(newValue) {
        panGesture.isEnabled = newValue
    }
}

override init(frame: CGRect) {
    super.init(frame: frame)
    setupViews()
    setupGesture()
}

private func setupViews() {
    addSubview(visableView)
    visableView.addSubview(label)

    visableView.edgesToSuperview()
    label.edgesToSuperview()

}

private func setupGesture() {
    panGesture = UIPanGestureRecognizer(target: self, action: #selector(swipe(_:)))
    panGesture.delegate = self
    addGestureRecognizer(panGesture)
}

@objc func swipe(_ sender:UIPanGestureRecognizer) {
    let translation = sender.translation(in: self)
    let newXPosition = center.x + translation.x
    let velocity = sender.velocity(in: self)

    switch(sender.state) {

    case .changed:
        let shouldSwipeRight = translation.x > 0 && newXPosition < originalXCenter
        let shouldSwipeLeft = translation.x < 0 && newXPosition > originalXCenter - maxSwipe
        guard shouldSwipeRight || shouldSwipeLeft else { break }
            center.x = newXPosition
    case .ended:
        if -velocity.x > highVelocity {
            center.x = originalXCenter - maxSwipe
            break
        }
        guard center.x > originalXCenter - maxSwipe - swipeBufffer, center.x < originalXCenter - maxSwipe + swipeBufffer, velocity.x < highVelocity  else {
            center.x = originalXCenter
            break
        }
    default:
        break
    }
    panGesture.setTranslation(.zero, in: self)
}

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

}

extension SwipeView: UIGestureRecognizerDelegate {
func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
    return true
}
}

UICollectionViewCell 中嵌入可交换视图：

import UIKit
import TinyConstraints

protocol DeleteCellDelegate {
func deleteCell(_ sender : UIButton)
}

class SwipeableCell: UICollectionViewCell {

lazy var deleteButton: UIButton = {
    let button = UIButton()
    button.backgroundColor = .red
    button.addTarget(self, action: #selector(didPressedButton(_:)), for: .touchUpInside)
    button.titleLabel?.text = "Delete"
    return button
}()

var deleteCellDelegate: DeleteCellDelegate?

@objc private func didPressedButton(_ sender: UIButton) {
    deleteCellDelegate?.deleteCell(sender)
    print("delete")
}
let swipeableview: SwipeView = {
    return SwipeView()
}()

override init(frame: CGRect) {
    super.init(frame: frame)
    addSubview(deleteButton)
    addSubview(swipeableview)
    swipeableview.edgesToSuperview()

    deleteButton.edgesToSuperview(excluding: .left, usingSafeArea: true)
    deleteButton.width(bounds.width * 0.3)
    swipeableview.maxSwipe = deleteButton.bounds.width

}

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}
}

一个示例视图控制器：

import UIKit
import TinyConstraints

class ViewController: UIViewController, DeleteCellDelegate {

func deleteCell(_ sender: UIButton) {
    let indexPath = IndexPath(item: sender.tag, section: 0)
    items.remove(at: sender.tag)
    collectionView.deleteItems(at: [indexPath])
}

lazy var collectionView: UICollectionView = {
    let layout = UICollectionViewFlowLayout()
    layout.itemSize = CGSize(width: view.bounds.width, height: 40)
    layout.sectionInset = UIEdgeInsets(top: 8, left: 8, bottom: 8, right: 8)
    let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
    cv.backgroundColor = .yellow
    cv.isPagingEnabled = true
    cv.isUserInteractionEnabled = true
    return cv
}()

var items  = ["1", "2", "3"]

override func viewDidLoad() {
    super.viewDidLoad()
    view.addSubview(collectionView)
    collectionView.delegate = self
    collectionView.dataSource = self
    collectionView.edgesToSuperview(usingSafeArea: true)
    collectionView.register(SwipeableCell.self, forCellWithReuseIdentifier: "cell")
    let panGesture = UIPanGestureRecognizer()
    view.addGestureRecognizer(panGesture)
    panGesture.delegate = self
}

}

extension ViewController: UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return items.count
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! SwipeableCell
    cell.backgroundColor = .blue
    cell.swipeableview.label.text = items[indexPath.item]
    cell.deleteButton.tag = indexPath.item
    cell.deleteCellDelegate = self
    return cell
}

func collectionView(_ collectionView: UICollectionView, performAction action: Selector, forItemAt indexPath: IndexPath, withSender sender: Any?) {
}

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
}

}

extension ViewController: UIGestureRecognizerDelegate {
func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
    return false
}
}