ios - 检测何时取消 3D Touch Peek 和 Pop View

Question

我有一个带有 3D Touch 的 UITableView Peek and Pop启用。我希望能够检测到用户何时查看 View 以及何时用户停止查看 View 而不弹出。我知道 previewingGestureRecognizerForFailureRelationship存在。我试过这样使用它:

func previewingContext(_ previewingContext: UIViewControllerPreviewing, viewControllerForLocation location: CGPoint) -> UIViewController? {

        // Here's where I add the gesture
        let gesture = previewingContext.previewingGestureRecognizerForFailureRelationship
        gesture.addObserver(self, forKeyPath: "state", options: .new, context: nil)

        let sb = UIStoryboard(name: "Main", bundle: nil)
        let detailVC = sb.instantiateViewController(withIdentifier: "SongPreviewViewController") as? SongPreviewViewController

        return detailVC
    }

然后我添加

override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {

        // can recognize peeking and canceling commit
        if let object = object {
            if keyPath == "state" {
                let newValue = (change![NSKeyValueChangeKey.newKey]! as AnyObject).integerValue
                let state = UIGestureRecognizerState(rawValue: newValue!)!
                switch state {
                case .possible:
                    print("switch - possible")
                case .began:
                    print("switch - began")
                case .changed:
                    print("switch - changed")
                case .ended:
                    print("switch - ended")
                case .cancelled:
                    print("switch - cancelled")
                case .failed:
                    print("switch - failed")
                }
            }
        }
    }

但是每次 peek View 开始时，都会调用 .ended。有谁知道如何正确执行此操作？ Here's the reference I used for this code.感谢您的帮助!

Answer 1

UITapGestureRecognizer 仅在手势状态为 UIGestureRecognizerStateEnded 时触发，如以下链接所述:

About messages from UITapGestureRecognizer

所有手势识别器在可能状态(可能)中开始多点触摸序列。如果您希望获得最多两种状态:(.Possible) 和 < strong>(.end) 你可以试试这个代码(Xcode 版本 9.2，swift 3.2，目标 11.2)。

1. 更改您的 addObserver 代码(添加了更多选项):

   gesture.addObserver(self, forKeyPath: "state", options: [.prior, .old, .new], context: nil)
   

2. 在您的 observeValue 方法中获取旧值和新值，如下所示。它将调用(.possible) 和(.end) 状态:

   override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {     
   // can recognize peeking and canceling commit
   if let object = object {
       if keyPath == "state" {
           var newValue:Int?
           guard let change = change else { return }
           let old = change[.oldKey] == nil || change[.oldKey] as? NSNull != nil ? "nil" : "\(change[.oldKey]!)"
           let new = change[.newKey] == nil || change[.newKey] as? NSNull != nil ? "nil" : "\(change[.newKey]!)"
           if change[.notificationIsPriorKey] as? Bool == true {
               newValue = (old as AnyObject).integerValue
           }
           else {
                newValue = (new as AnyObject).integerValue
           }
           let state = UIGestureRecognizerState(rawValue: newValue!)!
           switch state {
           case .possible:
               print("switch - possible")
           case .began:
               print("switch - began")
           case .changed:
               print("switch - changed")
           case .ended:
               print("switch - ended")
           case .cancelled:
               print("switch - cancelled")
           case .failed:
               print("switch - failed")
           }
       }
   }