像Snapchat [SWIFT 3]

Question

我正在尝试创建一个可以像Snapchat一样移动的TextView。我做了类似的东西，虽然当你尝试旋转时进行缩放时，它往往会无限地水平拉伸，拖动有时可能会有点儿。

我有这个：

func panGesture(pan: UIPanGestureRecognizer) {
    print("Being Dragged")
    if pan.state == .began {
        textViewOrigin = pan.location(in: textView)
    }else {
        let location = pan.location(in: view) // get pan location
        textView.frame.origin = CGPoint(x: location.x - textViewOrigin.x, y: location.y - textViewOrigin.y)
    }
}
func scaleGesture(_ gesture: UIPinchGestureRecognizer){
    print("Being Scaled")
    switch gesture.state{
    case.began:
        identity = textView.transform
    case.changed,.ended:
        textView.transform = identity.scaledBy(x: gesture.scale, y: gesture.scale)
    default:
        break
    }
}
func rotationGesture(sender: UIRotationGestureRecognizer){
    print("Being Rotated")
    textView.transform = textView.transform.rotated(by: sender.rotation)
    sender.rotation = 0
}

我正在努力实现这个目标：

如果有人可以帮助改变或重新编写我认为非常好的代码，请提前感谢！

Answer 1

默认情况下，在视图上的一个手势识别器开始处理手势后，其他识别器将被忽略。可以通过覆盖方法（对于Swift）来控制此行为：

gestureRecognizer（_：shouldRecognizeSimultaneouslyWith：）

返回true。默认实现返回false。要覆盖该函数，只需将实现（返回true）添加到ViewController源代码文件中。

以下是一些示例Swift代码（请参阅https://developer.apple.com/documentation/uikit/uigesturerecognizerdelegate/1624208-gesturerecognizer?changes=_7）：

class ViewController: UIViewController,UIGestureRecognizerDelegate {

    @IBOutlet var textField: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        //add pan gesture
        let gestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(handlePan))
        gestureRecognizer.delegate = self
        textField.addGestureRecognizer(gestureRecognizer)

        //Enable multiple touch and user interaction for textfield
        textField.isUserInteractionEnabled = true
        textField.isMultipleTouchEnabled = true

        //add pinch gesture
        let pinchGesture = UIPinchGestureRecognizer(target: self, action:#selector(pinchRecognized(pinch:)))
        pinchGesture.delegate = self
        textField.addGestureRecognizer(pinchGesture)

        //add rotate gesture.
        let rotate = UIRotationGestureRecognizer.init(target: self, action: #selector(handleRotate(recognizer:)))
        rotate.delegate = self
        textField.addGestureRecognizer(rotate)


    }

    func handlePan(_ gestureRecognizer: UIPanGestureRecognizer) {
        if gestureRecognizer.state == .began || gestureRecognizer.state == .changed {

            let translation = gestureRecognizer.translation(in: self.view)
            // note: 'view' is optional and need to be unwrapped
            gestureRecognizer.view!.center = CGPoint(x: gestureRecognizer.view!.center.x + translation.x, y: gestureRecognizer.view!.center.y + translation.y)
            gestureRecognizer.setTranslation(CGPoint.zero, in: self.view)
        }

    }

    func pinchRecognized(pinch: UIPinchGestureRecognizer) {

        if let view = pinch.view {
            view.transform = view.transform.scaledBy(x: pinch.scale, y: pinch.scale)
            pinch.scale = 1
        }
    }

    func handleRotate(recognizer : UIRotationGestureRecognizer) {
        if let view = recognizer.view {
            view.transform = view.transform.rotated(by: recognizer.rotation)
            recognizer.rotation = 0
        }
    }

    //MARK:- UIGestureRecognizerDelegate Methods
    func gestureRecognizer(_: UIGestureRecognizer,
        shouldRecognizeSimultaneouslyWith shouldRecognizeSimultaneouslyWithGestureRecognizer:UIGestureRecognizer) -> Bool {
        return true
    }
}

在Objective C中，重写函数函数就是这个（参见https://developer.apple.com/documentation/uikit/uigesturerecognizerdelegate/1624208-gesturerecognizer?language=objc）：

-(BOOL)gestureRecognizer:(UIGestureRecognizer*)aR1 shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)aR2
    {
    return YES;
    }

Answer 2

我编写了一个易于使用的类。

基本用法：

// define 
var snapGesture: SnapGesture?

// add gesture
self.snapGesture = SnapGesture(view: self.testView!)

// remove gesture
self.snapGesture = nil

高级用法，用于视图接收手势为背景视图的情况：

// add gesture
self.snapGesture = SnapGesture(transformView: self.testView!, gestureView: self.view)

// remove gesture
self.snapGesture = nil

班级：

import UIKit

/*
 usage:

    add gesture:
        yourObjToStoreMe.snapGesture = SnapGesture(view: your_view)
    remove gesture:
        yourObjToStoreMe.snapGesture = nil
    disable gesture:
        yourObjToStoreMe.snapGesture.isGestureEnabled = false
    advanced usage:
        view to receive gesture(usually superview) is different from view to be transformed,
        thus you can zoom the view even if it is too small to be touched.
        yourObjToStoreMe.snapGesture = SnapGesture(transformView: your_view_to_transform, gestureView: your_view_to_recieve_gesture)

 */

class SnapGesture: NSObject, UIGestureRecognizerDelegate {

    // MARK: - init and deinit
    convenience init(view: UIView) {
        self.init(transformView: view, gestureView: view)
    }
    init(transformView: UIView, gestureView: UIView) {
        super.init()

        self.addGestures(v: gestureView)
        self.weakTransformView = transformView
    }
    deinit {
        self.cleanGesture()
    }

    // MARK: - private method
    private weak var weakGestureView: UIView?
    private weak var weakTransformView: UIView?

    private var panGesture: UIPanGestureRecognizer?
    private var pinchGesture: UIPinchGestureRecognizer?
    private var rotationGesture: UIRotationGestureRecognizer?

    private func addGestures(v: UIView) {

        panGesture = UIPanGestureRecognizer(target: self, action: #selector(panProcess(_:)))
        v.isUserInteractionEnabled = true
        panGesture?.delegate = self     // for simultaneous recog
        v.addGestureRecognizer(panGesture!)

        pinchGesture = UIPinchGestureRecognizer(target: self, action: #selector(pinchProcess(_:)))
        //view.isUserInteractionEnabled = true
        pinchGesture?.delegate = self   // for simultaneous recog
        v.addGestureRecognizer(pinchGesture!)

        rotationGesture = UIRotationGestureRecognizer(target: self, action: #selector(rotationProcess(_:)))
        rotationGesture?.delegate = self
        v.addGestureRecognizer(rotationGesture!)

        self.weakGestureView = v
    }

    private func cleanGesture() {
        if let view = self.weakGestureView {
            //for recognizer in view.gestureRecognizers ?? [] {
            //    view.removeGestureRecognizer(recognizer)
            //}
            if panGesture != nil {
                view.removeGestureRecognizer(panGesture!)
                panGesture = nil
            }
            if pinchGesture != nil {
                view.removeGestureRecognizer(pinchGesture!)
                pinchGesture = nil
            }
            if rotationGesture != nil {
                view.removeGestureRecognizer(rotationGesture!)
                rotationGesture = nil
            }
        }
        self.weakGestureView = nil
        self.weakTransformView = nil
    }




    // MARK: - API

    private func setView(view:UIView?) {
        self.setTransformView(view, gestgureView: view)
    }

    private func setTransformView(_ transformView: UIView?, gestgureView:UIView?) {
        self.cleanGesture()

        if let v = gestgureView  {
            self.addGestures(v: v)
        }
        self.weakTransformView = transformView
    }

    open func resetViewPosition() {
        UIView.animate(withDuration: 0.4) {
            self.weakTransformView?.transform = CGAffineTransform.identity
        }
    }

    open var isGestureEnabled = true

    // MARK: - gesture handle

    // location will jump when finger number change
    private var initPanFingerNumber:Int = 1
    private var isPanFingerNumberChangedInThisSession = false
    private var lastPanPoint:CGPoint = CGPoint(x: 0, y: 0)
    @objc func panProcess(_ recognizer:UIPanGestureRecognizer) {
        if isGestureEnabled {
            //guard let view = recognizer.view else { return }
            guard let view = self.weakTransformView else { return }

            // init
            if recognizer.state == .began {
                lastPanPoint = recognizer.location(in: view)
                initPanFingerNumber = recognizer.numberOfTouches
                isPanFingerNumberChangedInThisSession = false
            }

            // judge valid
            if recognizer.numberOfTouches != initPanFingerNumber {
                isPanFingerNumberChangedInThisSession = true
            }
            if isPanFingerNumberChangedInThisSession {
                return
            }

            // perform change
            let point = recognizer.location(in: view)
            view.transform = view.transform.translatedBy(x: point.x - lastPanPoint.x, y: point.y - lastPanPoint.y)
            lastPanPoint = recognizer.location(in: view)
        }
    }



    private var lastScale:CGFloat = 1.0
    private var lastPinchPoint:CGPoint = CGPoint(x: 0, y: 0)
    @objc func pinchProcess(_ recognizer:UIPinchGestureRecognizer) {
        if isGestureEnabled {
            guard let view = self.weakTransformView else { return }

            // init
            if recognizer.state == .began {
                lastScale = 1.0;
                lastPinchPoint = recognizer.location(in: view)
            }

            // judge valid
            if recognizer.numberOfTouches < 2 {
                lastPinchPoint = recognizer.location(in: view)
                return
            }

            // Scale
            let scale = 1.0 - (lastScale - recognizer.scale);
            view.transform = view.transform.scaledBy(x: scale, y: scale)
            lastScale = recognizer.scale;

            // Translate
            let point = recognizer.location(in: view)
            view.transform = view.transform.translatedBy(x: point.x - lastPinchPoint.x, y: point.y - lastPinchPoint.y)
            lastPinchPoint = recognizer.location(in: view)
        }
    }


    @objc func rotationProcess(_ recognizer: UIRotationGestureRecognizer) {
        if isGestureEnabled {
            guard let view = self.weakTransformView else { return }

            view.transform = view.transform.rotated(by: recognizer.rotation)
            recognizer.rotation = 0
        }
    }


    //MARK:- UIGestureRecognizerDelegate Methods
    func gestureRecognizer(_: UIGestureRecognizer,
                           shouldRecognizeSimultaneouslyWith shouldRecognizeSimultaneouslyWithGestureRecognizer:UIGestureRecognizer) -> Bool {
        return true
    }

}

现在，您到此为止，请继续。 如您所知，superView中的手势可能会吃掉subView的事件，而在gmail示例中，手势将吃掉工具栏的事件，因此，如果我们触摸工具栏，则需要防止任何手势被Superview识别。

这个想法是向工具栏添加一个pseduo定制手势，因此将阻止任何手势进行超级视图，并且该pseduo手势除了将手势或事件传递到子视图或自己的视图外，什么也不做。

在这里，我还编写了一个易于使用的类。

用法：

   toolbarView.addGestureRecognizer(SnapBlockGestureRecognizer)

实现：

import UIKit

class SnapBlockGestureRecognizer: UIGestureRecognizer {

    init() {
        //self.init(target: self, action: #selector(__dummyAction))
        super.init(target: nil, action: nil)

        self.addTarget(self, action: #selector(__dummyAction))
        self.cancelsTouchesInView = false
    }

    override init(target: Any?, action: Selector?) {
        super.init(target: target, action: action)

        self.cancelsTouchesInView = false
    }

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {
        if self.state == .possible {
            self.state = .began
        }
    }

    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent) {
    }

    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent) {
        self.state = .recognized
    }

    override func canBePrevented(by preventingGestureRecognizer: UIGestureRecognizer) -> Bool {
        return self.isGestureRecognizerAllowed(gr:preventingGestureRecognizer)
    }


    override func canPrevent(_ preventedGestureRecognizer: UIGestureRecognizer) -> Bool {
        return !(self.isGestureRecognizerAllowed(gr: preventedGestureRecognizer))
    }

    override func shouldBeRequiredToFail(by otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        return !(self.isGestureRecognizerAllowed(gr: otherGestureRecognizer))
    }

    override func shouldRequireFailure(of otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        return false
    }

    func isGestureRecognizerAllowed(gr: UIGestureRecognizer) -> Bool {
        return gr.view!.isDescendant(of: self.view!)
    }

    @objc func __dummyAction() {
        // do nothing
        // print("dummyAction")
    }
}