UIPanGestureRecognizer不会触发操作

Question

我正在尝试创建UIView的子类，以便通过平移来扩展视图。它应该以这种方式工作：如果用户向顶部平移，视图的高度会降低，相反，如果平移器朝向底部，则应该增加。为了实现该功能，我正在尝试向视图添加UIPanGestureRecognizer，但它似乎不起作用。我这样做了：

第一个片段是uiView子类声明

class ExpandibleView: UIView {
    //Here I create the reference to the recognizer
    let panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(handlePan(_:)))

    //And here I set its minimumNumberOfTouches and maximumNumberOfTouches properties and add it to the view
    func initialize() {
        panGestureRecognizer.minimumNumberOfTouches = 1
        panGestureRecognizer.maximumNumberOfTouches = 1
        self.addGestureRecognizer(panGestureRecognizer)
    }

    //here's the function that should handle the pan but who instead doesn't seem to been called at all
    @objc func handlePan(_ sender:UIPanGestureRecognizer) {
        //Here's I handle the Pan
    }
}

第二个是View Controller中的实现。

class MapViewController: UIViewController {
    @IBOutlet weak var profileView: ExpandibleView!

    //MARK: - ViewController Delegate Methods

    override func viewDidLoad() {
        super.viewDidLoad()

        //Here I set the View
        profileView.isUserInteractionEnabled = true
        profileView.initialize()
        profileView.minHeight = 100
        profileView.maxHeight = 190
    }

}

我在故事板中设置了视图的类作为我创建的子类，但识别器不会触发所有处理程序。

Answer 1

您遇到的问题是由于您在类定义中定义了panGestureRecognizer变量：

//Here I create the reference to the recognizer
let panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(handlePan(_:)))

你可以用这种方式初始化它，但是在创建这个变量时似乎没有设置self。所以你的行动从未登记过。

有几种方法可以使用代码修复此问题，您可以继续将其初始化为实例变量，但是您需要在initialize()函数中设置目标/操作

let panGestureRecognizer = UIPanGestureRecognizer()

func initialize() {
    // add your target/action here
    panGestureRecognizer.addTarget(self, action: #selector(handlePan(_:)))
    panGestureRecognizer.minimumNumberOfTouches = 1
    panGestureRecognizer.maximumNumberOfTouches = 1
    addGestureRecognizer(panGestureRecognizer)
}

或者您可以在初始化函数中初始化手势识别器，而不是使用实例变量

func initialize() {
    let panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(handlePan(_:)))
    panGestureRecognizer.minimumNumberOfTouches = 1
    panGestureRecognizer.maximumNumberOfTouches = 1
    addGestureRecognizer(panGestureRecognizer)
}

我原来的答案

这是一个解决方案，它使用带有故事板中定义的视图的约束或直接操作框架。

带约束的示例

import UIKit

// Delegate protocol for managing constraint updates if needed
protocol MorphDelegate: class {

    // tells the delegate to change its size constraints
    func morph(x: CGFloat, y: CGFloat)
}

class ExpandableView: UIView {

    var delegate: MorphDelegate?

    init() {
        // frame is set later if needed by creator when using this init method
        super.init(frame: CGRect.zero)
        configureGestureRecognizers()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        configureGestureRecognizers()
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        configureGestureRecognizers()
    }

    // setup UIPanGestureRecognizer
    internal func configureGestureRecognizers() {
        let panGR = UIPanGestureRecognizer.init(target: self, action: #selector(didPan(_:)))
        addGestureRecognizer(panGR)
    }

    @objc func didPan(_ panGR: UIPanGestureRecognizer) {

        // get the translation
        let translation = panGR.translation(in: self).applying(transform)

        if let delegate = delegate {

            // tell delegate to change the constraints using this translation
            delegate.morph(x: translation.x, y: translation.y)

        } else {

            // If you want the view to expand/contract in opposite direction
            // of drag then swap the + and - in the 2 lines below
            let newOriginY = frame.origin.y + translation.y
            let newHeight = frame.size.height - translation.y

            // expand self via frame manipulation
            let newFrame = CGRect(x: frame.origin.x, y: newOriginY, width: frame.size.width, height: newHeight)
            frame = newFrame
        }

        // reset translation
        panGR.setTranslation(CGPoint.zero, in: self)
    }

}

如果你想通过在故事板中定义它并操纵它的约束来使用这个类，你可以像这样去做。

首先在故事板中定义您的视图并约束它的宽度和高度。对于演示，我将它的x位置限制在视图中心，它位于SafeArea.bottom的底部

为视图创建一个IBOutlet，以及它对ViewController文件的高度约束。

我为此示例将背景颜色设置为蓝色。

在视图控制器中，我定义了一个设置视图的函数（当前只设置约束操作回调的委托），然后定义了一个扩展来处理委托调用以更新约束。

class ViewController: UIViewController {

    @IBOutlet weak var expandingView: ExpandableView!
    @IBOutlet weak var constraint_expViewHeight: NSLayoutConstraint!


    override func viewDidLoad() {
        super.viewDidLoad()

        // call to configure our expanding view
        configureExpandingView()
    }

    // this sets the delegate for an expanding view defined in the storyboard
    func configureExpandingView() {
        expandingView.delegate = self
    }
}

// setup the delegate callback to handle constraint manipulation
extension ViewController: MorphDelegate {

    func morph(x: CGFloat, y: CGFloat) {

        // this will update the view's height based on the amount
        // you drag your finger in the view. You can '+=' below if
        // you want to reverse the expanding behavior based on pan
        // movements.
        constraint_expViewHeight.constant -= y
    }
}

通过约束这样做我在运行项目时给出了这个：

框架操作的示例

要使用它并仅使用frame属性操作高度，视图控制器可能会实现如下所示的视图创建：

override func viewDidLoad() {
    super.viewDidLoad()

    setupExpandingView()
}

func setupExpandingView() {

    let newView = ExpandableView()
    newView.backgroundColor = .red
    newView.frame = CGRect(x: 20, y: 200, width: 100, height: 100)
    view.addSubview(newView)
}

使用框架操作我得到这个：

Answer 2

尝试改变这个

class ExpandibleView: UIView {

    func initialize() {


    }

    //here's the function that should handle the pan but who instead doesn't seem to been called at all
     func handlePan() {
        //your function
    }
}

class MapViewController: UIViewController {
    @IBOutlet weak var profileView: ExpandibleView!

    //MARK: - ViewController Delegate Methods

    override func viewDidLoad() {
        super.viewDidLoad()
     let panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(handlePan(_:)))
     panGestureRecognizer.minimumNumberOfTouches = 1
        panGestureRecognizer.maximumNumberOfTouches = 1
     profileView.addGestureRecognizer(panGestureRecognizer)
        //Here I set the View
        profileView.isUserInteractionEnabled = true
        profileView.initialize()
        profileView.minHeight = 100
        profileView.maxHeight = 190
    }

   @objc func handlePan(_ sender:UIPanGestureRecognizer) {
       profileView.handlePan()
    }
}

或者您可以在其他视图中为呼叫创建委托。

祝好运！