能够缩短UIDragInteraction的长按时间

问题描述

我目前正在使用iOS 11中提供的 UIDragInteraction 和 UIDropInteraction 来提供简单的拖放功能，

我意识到一个不直观的元素是 UIDragInteraction 需要长按至少一秒钟才能起作用。我想知道是否有一种方法可以缩短长按时间？？似乎并未强调这一点。

谢谢！

以下粘贴的实现以供参考：

  class ViewController：UIViewController { 
 
 @IBOutlet var imageView：UIImageView！ 
 @IBOutlet var dropArea：UIImageView！ 
 
重写func viewDidLoad（）{
 super.viewDidLoad（）
 
 let dragInteraction = UIDragInteraction（委托：自我）
 imageView.addInteraction（dragInteraction） 
 dragInteraction.isEnabled = true 
 let dropInteraction = UIDropInteraction（代表：自我）
 dropArea.addInteraction（dropInteraction）
} 
} 
 
扩展ViewController：UIDragInteractionDelegate {
 func dragInteraction（_交互：UIDragInteraction，itemsForBeginning会话：UIDragSession）-> [UIDragItem] {
保护let image = imageView.image 
 else {return []} 
 
 let itemProvider = NSItemProvider（object：image）
 return [UIDragItem（ itemProvider：itemProvider）] 
} 
} 
 
扩展ViewController：UIDropInteractionDelegate {
 func dropInteraction（_交互：UIDropInteraction，sessionDidUpdate会话：UIDropSession）-> UIDropProposal {
 return UIDropProposal（operation：.copy）
} 
 
 func dropInteraction（_交互作用：UIDropInteraction，performDrop会话：UIDropSession）{
保护对象让itemProvider =会话.items.first？.itemProvider，
 itemProvider.canLoadObject（ofClass：UIImage.self）
 else {return} 
 
 itemProvider.loadObject（ofClass：UIImage.self）{[弱自我] loadedItem，
防护中的错误让image = loadedItem为？ UIImage 
 else {return} 
 
 DispatchQueue.main.async {
 self？.dropArea.image = image 
} 
} 
} 
} 
  

解决方案

没有明显的方法这，但是我正面临着同样的问题，并偷看了dragInteraction附加到的视图的手势识别器。它是 _UIDragLiftGestureRecognizer ，它不是公共API的一部分，但事实证明这只是 UILongPressGestureRecognizer 的子类。 / p>

因此，在将 UIDragInteraction 添加到视图后，以及将该视图添加到视图层次结构之后（自我使用的是自定义UIView子类，我刚刚将其添加到 didMoveToSuperview（））中，您可以执行以下操作：

 如果让longPressRecognizer = poseRecognizers？.compactMap（{$ 0 as？UILongPressGestureRecognizer}）。first {
 longPressRecognizer.minimumPressDuration = 0.1 //您的自定义值
} 
  

I am currently using UIDragInteraction and UIDropInteraction made available in iOS 11 to make a simple drag and drop feature, where user could drag an UIImageView onto a UIView.

I realized that one unintuitive element to this is that the UIDragInteraction requires a long press of at least a second to work. I was wondering if there is a way to shorten the long press duration? The docs on Apple doesn't seem to highlight this.

Thanks!

Implementation pasted below for reference:

class ViewController: UIViewController {

    @IBOutlet var imageView: UIImageView!
    @IBOutlet var dropArea: UIImageView!

    override func viewDidLoad() {
        super.viewDidLoad()

        let dragInteraction = UIDragInteraction(delegate: self)
        imageView.addInteraction(dragInteraction)
        dragInteraction.isEnabled = true
        let dropInteraction = UIDropInteraction(delegate: self)
        dropArea.addInteraction(dropInteraction)
    }
}

extension ViewController: UIDragInteractionDelegate {
    func dragInteraction(_ interaction: UIDragInteraction, itemsForBeginning session: UIDragSession) -> [UIDragItem] {
        guard let image = imageView.image
            else { return [] }

        let itemProvider = NSItemProvider(object: image)
        return [UIDragItem(itemProvider: itemProvider)]
    }
}

extension ViewController: UIDropInteractionDelegate {
    func dropInteraction(_ interaction: UIDropInteraction, sessionDidUpdate session: UIDropSession) -> UIDropProposal {
        return UIDropProposal(operation: .copy)
    }

    func dropInteraction(_ interaction: UIDropInteraction, performDrop session: UIDropSession) {
        guard let itemProvider = session.items.first?.itemProvider,
            itemProvider.canLoadObject(ofClass: UIImage.self)
            else { return }

        itemProvider.loadObject(ofClass: UIImage.self) { [weak self] loadedItem, error in
            guard let image = loadedItem as? UIImage
                else { return }

            DispatchQueue.main.async {
                self?.dropArea.image = image
            }
        }
    }
}

解决方案

There's no obvious way to do this, but I was just facing the same problem and took a peek into the gesture recognizers of the view that the dragInteraction is attached to. It a _UIDragLiftGestureRecognizer which is not part of the public API, but turns out this is just a subclass of UILongPressGestureRecognizer.

So, after having added your UIDragInteraction to your view, and after having added that view to the view hierachy (since I'm using a custom UIView subclass I just added it into didMoveToSuperview()), you can do something like this:

if let longPressRecognizer = gestureRecognizers?.compactMap({ $0 as? UILongPressGestureRecognizer}).first {
    longPressRecognizer.minimumPressDuration = 0.1 // your custom value
}

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