UIGestureRecognizer 子类——touchesMoved 自动改变状态为.changed

Question

我正在尝试创建一个 UIGestureRecognizer 子类，在 touchesMoved 中我没有代码，但 state 被设置为 .changed。

有谁知道为什么会这样？当我们处于 .changed 状态时，我需要能够自己决定。

如果我删除我的 touchesBegan 功能并且永远不会移动到 .began，则不会发生这种情况。

import UIKit.UIGestureRecognizerSubclass

class MyRecognizer: UIGestureRecognizer {

    private var refView: UIView? {
        return self.view?.window
    }


    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {
       super.touchesBegan(touches, with: event)

       if touches.count != 1 {
            state = .failed
            return
        }

        guard let location = touches.first?.location(in: refView) else {
            self.state = .failed
            return
        }

       state = .began

    }

    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent) {
        // there is no code here!
    }

   //This is how I'm debugging state
   override var state: UIGestureRecognizerState {
      get { return super.state }
      set {
          super.state = newValue
          print("state = \(newValue.debugDescription)")
      }  
    }

}

extension UIGestureRecognizerState: CustomDebugStringConvertible {
    public var debugDescription: String {
        switch self {
        case .began: return "began"
        case .possible: return "possible"
        case .changed: return "changed"
        case .ended: return "ended"
        case .cancelled: return "cancelled"
        case .failed: return "failed"
        }
    }
}

Answer 1

您的测试方法有缺陷。我试过了（这是我的测试应用程序的完整代码）：

import UIKit
import UIKit.UIGestureRecognizerSubclass

class MyRecognizer: UIGestureRecognizer {
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {
        super.touchesBegan(touches, with: event)
        print(self.state.rawValue)
    }
    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent) {
        super.touchesMoved(touches, with: event)
        print(self.state.rawValue)
    }
}

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        let g = MyRecognizer(target: self, action: #selector(grFired))
        self.view.addGestureRecognizer(g)
        // Do any additional setup after loading the view, typically from a nib.
    }

    @objc func grFired(_ g:UIGestureRecognizer) {
        print("here", g.state.rawValue)
    }

}

然后我拖到附加了手势识别器的背景视图上。我的手势识别器从未离开 possible 状态。

另请注意，您的预期可能不正确 ("I need to be able to decide for myself when we are in the .changed state")。正常且正确的行为是，在 touchesBegan 中声明状态为 .began 后，您的 touchesMoved 将以状态 .began 调用一次，手势识别器将立即前进到 .changed 自动。即正确；如果这是连续手势，那么当我们处于 .began 状态而不进入 .changed 状态时，就不可能发生 moved 事件。同样，这是一个测试：

import UIKit
import UIKit.UIGestureRecognizerSubclass

class MyRecognizer: UIGestureRecognizer {
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {
        super.touchesBegan(touches, with: event)
        if touches.count != 1 {
            state = .failed
            return
        }
        print(self.state.rawValue)
        self.state = .began
    }
    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent) {
        super.touchesMoved(touches, with: event)
        print("moved", self.state.rawValue)
    }
}

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        let g = MyRecognizer(target: self, action: #selector(grFired))
        self.view.addGestureRecognizer(g)
        // Do any additional setup after loading the view, typically from a nib.
    }

    @objc func grFired(_ g:UIGestureRecognizer) {
        print("here", g.state.rawValue)
    }

}

UIGestureRecognizer 子类——touchesMoved 自动改变状态为.changed

UIGestureRecognizer subclass-- touchesMoved automatically changes state to .changed

uigesturerecognizer

ios

swift