一种使用 UIPinchGestureRecognizer UIRotationGestureRecognizer 和 UIPanGestureRecognizer 添加类似 Instagram 的布局指南的方法？

Question

我使用 UIPinchGestureRecognizer UIPanGestureRecognizer & UIRotationGestureRecognizer 和 UILabel 来实现 Instagram 之类的缩放和拖动功能。现在我想显示布局指南，例如当UILabel 被拖到中心时，它应该显示布局指南，如下例所示。当您旋转UILabel 时，它还应该显示布局指南。

实现此功能的最佳且准确的方法是什么？

这是我已经拥有的

（图片取自this question@Skiddswarmik）

这是我用于简单拖动和缩放功能的代码（取自 this answer @lbsweek）

SnapGesture 类

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
    }

}

在UILabel中添加手势

// define 
var snapGesture: SnapGesture?

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

Answer 1

您将在下面找到您所描述的课程的更新版本。

大部分更新的代码位于接近末尾的最后一部分（指南），但我已经稍微更新了您的 UIGestureRecognizer 操作以及您的主要 init 方法。

特点：

- 用于水平居中视图位置的垂直参考线。

- 用于将视图旋转居中于 0 度的水平参考线。

- 位置和旋转捕捉到具有公差值的参考线（snapToleranceDistance 和 snapToleranceAngle 属性）。

- 指南的动画外观/消失（animateGuides 和 guideAnimationDuration 属性）。

- 可以根据用例更改的指南视图（movementGuideView 和 rotationGuideView 属性）

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

        guard let transformView = self.weakTransformView, let superview = transformView.superview else {
            return
        }

        // This is required in order to be able to snap the view to center later on,
        // using the `tx` property of its transform.
        transformView.center = superview.center
    }
    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) {
        guard isGestureEnabled, 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 {
            hideGuidesOnGestureEnd(recognizer)
            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)

        updateMovementGuide()
        hideGuidesOnGestureEnd(recognizer)
    }

    private var lastScale:CGFloat = 1.0
    private var lastPinchPoint:CGPoint = CGPoint(x: 0, y: 0)
    @objc func pinchProcess(_ recognizer:UIPinchGestureRecognizer) {
        guard isGestureEnabled, 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)
            hideGuidesOnGestureEnd(recognizer)
            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)

        updateMovementGuide()
        hideGuidesOnGestureEnd(recognizer)
    }


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

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

    func hideGuidesOnGestureEnd(_ recognizer: UIGestureRecognizer) {
        if recognizer.state == .ended {
            showMovementGuide(false)
            showRotationGuide(false)
        }
    }

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

    // MARK:- Guides

    var animateGuides = true
    var guideAnimationDuration: TimeInterval = 0.3

    var snapToleranceDistance: CGFloat = 5 // pts
    var snapToleranceAngle: CGFloat = 1    // degrees
                        * CGFloat.pi / 180 // (converted to radians)

    var movementGuideView: UIView = {
        let view = UIView()
        view.backgroundColor = UIColor.blue
        return view
    } ()

    var rotationGuideView: UIView = {
        let view = UIView()
        view.backgroundColor = UIColor.red
        return view
    } ()

    // MARK: Movement guide and snap

    func updateMovementGuide() {
        guard let transformView = weakTransformView, let superview = transformView.superview else {
            return
        }

        let transformX = transformView.frame.midX
        let superX = superview.bounds.midX

        if transformX - snapToleranceDistance < superX && transformX + snapToleranceDistance > superX {
            transformView.transform.tx = 0
            showMovementGuide(true)
        } else {
            showMovementGuide(false)
        }

        updateGuideFrames()
    }

    var isShowingMovementGuide = false

    func showMovementGuide(_ shouldShow: Bool) {
        guard isShowingMovementGuide != shouldShow,
            let transformView = weakTransformView,
            let superview = transformView.superview
            else { return }

        superview.insertSubview(movementGuideView, belowSubview: transformView)
        movementGuideView.frame = CGRect(
            x: superview.frame.midX,
            y: 0,
            width: 1,
            height: superview.frame.size.height
        )

        let duration = animateGuides ? guideAnimationDuration : 0
        isShowingMovementGuide = shouldShow
        UIView.animate(withDuration: duration) { [weak self] in
            self?.movementGuideView.alpha = shouldShow ? 1 : 0
        }
    }

    // MARK: Rotation guide and snap

    func updateRotationGuide() {
        guard let transformView = weakTransformView else {
            return
        }

        let angle = atan2(transformView.transform.b, transformView.transform.a)
        if angle > -snapToleranceAngle && angle < snapToleranceAngle {
            transformView.transform = transformView.transform.rotated(by: angle * -1)
            showRotationGuide(true)
        } else {
            showRotationGuide(false)
        }
    }

    var isShowingRotationGuide = false

    func showRotationGuide(_ shouldShow: Bool) {
        guard isShowingRotationGuide != shouldShow,
            let transformView = weakTransformView,
            let superview = transformView.superview
            else { return }

        superview.insertSubview(rotationGuideView, belowSubview: transformView)

        let duration = animateGuides ? guideAnimationDuration : 0
        isShowingRotationGuide = shouldShow
        UIView.animate(withDuration: duration) { [weak self] in
            self?.rotationGuideView.alpha = shouldShow ? 1 : 0
        }
    }

    func updateGuideFrames() {
        guard let transformView = weakTransformView,
            let superview = transformView.superview
            else { return }

        rotationGuideView.frame = CGRect(
            x: 0,
            y: transformView.frame.midY,
            width: superview.frame.size.width,
            height: 1
        )
    }
}

对于任何感兴趣的人，这里有一个 test project 使用这个类。