iOS touchesMoved 仅由 UIButton 转发一次

Question

我的目标，同时拥有：

• 处理事件的 UIButton (.touchDown)
• 接收touchBegan/Moved/Ended/Cancelled的层次结构中的另一个上层视图（即：super）。

我想要那个事件，因为我需要触摸力和其他东西来进行一些计算

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在upper/super视图中，我覆盖了touchesBegan和friends，这样我就可以得到forces和东西了。

但是，基本上，UIButton 不会转发触摸事件，因此（在此示例中）我扩展了 UIButton（在我的代码中我扩展了一个子类〜但这不会改变问题）并覆盖 touchesBegan 和朋友，并在其中添加next?.touchesBegan(...)。

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什么有效：

• touchesBegan(...) 正确转发到超级视图

什么不起作用：

• touchesMoved(...) 仅转发一次 到其super 视图。 （即使按钮的touchesMoved 被调用并且next? 不是nil
• touchesEnded(...) 是NOT CALLED，当touchesMoved(...) 之前被调用时（如果你跟随，只有一次 touchesMoved(...) 调用）。又一次next? 不是nil

// One of the overrided UIButton touches event
extension UIButton {
    open override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        print("Button: touches began - ")
        super.touchesBegan(touches, with: event)
        next?.touchesBegan(touches, with: event)
        if next == nil { print("next was nil!") }
        print("Button: touches began - end\n")
    }
}

// One of the overrided ViewController touches event
// (which is only called once for touchesMoved, and then touchesEnded not called)
extension ViewController {
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        print("ViewController: touches began - ")
        super.touchesBegan(touches, with: event)
        print("ViewController: touches began - end\n")
    }
}

Here is an example project to show you the problem:

• git clone git@bitbucket.org:5t4rrk/problemtouchmovedonlyonce.git

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如果有人对为什么会出现这种行为有任何见解，请告诉我\o/

Answer 1

我使用UIGestureRecognizer 的子类尝试了一种稍微不同的方法。根据您的示例项目查看下面的代码。有趣的是，UIButton 似乎正在检查 touchesBegan 设置的状态.begin。可以将您的代码更改为不在 touchesBegan 方法中设置状态。看看这是否适合你。

UIKit 手势识别器还为您提供了一些委托方法和使用选择器的选项，该选择器可以访问由 touches... 方法设置的状态。但它们并没有为您提供每次触摸的那么多信息。

来源：

developer.apple.com/documentation/uikit/touche developer.apple.com/documentation/uikit/uigesturer

raywenderlich.com/6747815-uigesturerecognizer-tu

代码：

class ViewController: UIViewController {
    @IBOutlet weak var button: UIButton!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        button.addTarget(self, action: #selector(buttonTouched), for: .touchDown)
        
        let gesture = CustomGesture()
        self.view.addGestureRecognizer(gesture)
        self.view.isUserInteractionEnabled = true
    }
    
    @objc
    func buttonTouched(button:UIButton) {
        print("Button ACTION!")
    }
}

class CustomGesture: UIGestureRecognizer {
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {
        super.touchesBegan(touches, with: event)
        print("ViewController: touches began")
        //  state = .began //Do not set the state to .began as this seems to be blocking the UIButton gesture.
    }
    
    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesMoved(touches, with: event!)
        for _ in touches {
            print("ViewController: touches moved")
        }
        state = .changed
    }
    
    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesEnded(touches, with: event!)
        print("ViewController: touches ended")
        state = .ended
    }
    
    override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesCancelled(touches, with: event!)
        print("ViewController: touches cancelled")
        state = .cancelled
    }
}