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使用扩展名创建可单击的UIImageView

swift-extensions clickable uiimageview swift ios

Charlie Fish · 技术社区 · 8 年前

我有以下的Swift代码。

extension UIImageView {
    func enableClickablePrint() {
        let imageTap = UITapGestureRecognizer(target: self, action: #selector(imageTapped))
        self.addGestureRecognizer(imageTap)
        self.isUserInteractionEnabled = true
    }
    func disableClickablePrint() {
        // HERE
    }
    func toggleClickablePrint() {
        // HERE
    }

    @objc fileprivate func imageTapped(_ sender: UITapGestureRecognizer) {
        print("Image tapped")
    }
}

disableClickablePrint 和 toggleClickablePrint 功能。

extension UIImageView {
    var imageTap: UITapGestureRecognizer?
    func enableClickablePrint() {
        imageTap = UITapGestureRecognizer(target: self, action: #selector(imageTapped))
        self.addGestureRecognizer(imageTap)
        self.isUserInteractionEnabled = true
    }
    func disableClickablePrint() {
        if let theImageTap = imageTap {
            self.removeGestureRecognizer(theImageTap)
            imageTap = nil
        }
    }
    func toggleClickablePrint() {
        if let theImageTap = imageTap {
            disableClickablePrint()
        } else {
            enableClickablePrint()
        }
    }

    @objc fileprivate func imageTapped(_ sender: UITapGestureRecognizer) {
        print("Image tapped")
    }
}

但问题当然是你不能像我想做的那样在扩展中存储属性。

正确的做法是将其转换为UIImageView的子类吗?如果可能的话,我想尽量避免这种情况,因为如果我想把它变成一个框架或库或其他东西,子类就不能很好地集成到接口生成器中,开发人员就必须添加额外的步骤来更改所有图像视图的类。如果可能的话,我认为这是一个很好的选择。

3 回复 | 直到 8 年前

vacawama 8 年前

你的问题是你需要能够识别 UIGestureRecognizer 您添加了,但不能将其存储在属性中。

下面是一个(经过测试的)解决方案 UITapGestureRecognizer 手势识别器 self.gestureRecognizers 具有 first(where:)

extension UIImageView {

    class _CFTapGestureRecognizer : UITapGestureRecognizer { }

    private var _imageTap: _CFTapGestureRecognizer? { return self.gestureRecognizers?.first(where: { $0 is _CFTapGestureRecognizer }) as? _CFTapGestureRecognizer }

    func enableClickablePrint() {
        // Only enable once
        if _imageTap == nil {
            let imageTap = _CFTapGestureRecognizer(target: self, action: #selector(imageTapped))
            self.addGestureRecognizer(imageTap)
            self.isUserInteractionEnabled = true
        }
    }

    func disableClickablePrint() {
        if let theImageTap = _imageTap {
            self.removeGestureRecognizer(theImageTap)
        }
    }

    func toggleClickablePrint() {
        if _imageTap == nil {
            enableClickablePrint()
        } else {
            disableClickablePrint()
        }
    }

    @objc fileprivate func imageTapped(_ sender: UITapGestureRecognizer) {
        print("Image tapped")
    }
}

-1

Pranav Wadhwa 8 年前

可以使用getter/setter生成扩展变量:

extension UIImageView {

var tap: UITapGestureRecognizer {
    get {
        return //the created tap
    }
    set(value) {
        print(value)
    }
}

}

-1

mojtaba al moussawi 8 年前

由于swift中的扩展不能包含存储的属性,以下是解决方案:

objc_getAssociatedObject 和 objc_setAssociatedObject

好吧,这是一个很好的解决方案,但如果有纯粹的快速方法来做到这一点,为什么不!

在扩展中,用要使用的字段定义一个结构,例如 UITapGestureRecognizer

将此结构创建为private当然不需要任何人来访问它。

通过这样做,你已经达到了你所需要的,而你根本不用目标C。

例子:

extension UIImageView {
    private struct TapGestureHelper{
        static var tapGestureRecognizer : UITapGestureRecognizer?
    }

    var imageTap: UITapGestureRecognizer?{
        get {
            return TapGestureHelper.tapGestureRecognizer
        }
        set {
            TapGestureHelper.tapGestureRecognizer = newValue
        }
    }

    func enableClickablePrint() {
        imageTap = UITapGestureRecognizer(target: self, action: #selector(imageTapped))
        self.addGestureRecognizer(imageTap!)
        self.isUserInteractionEnabled = true
    }

    func disableClickablePrint() {
          guard let gesture = self.gestureRecognizers?.first else {
              return
          }
          self.removeGestureRecognizer(gesture)
          self.imageTap = nil
    }

    func toggleClickablePrint() {
        if let theImageTap = imageTap {
            disableClickablePrint()
        } else {
            enableClickablePrint()
        }
    }

    @objc fileprivate func imageTapped(_ sender: UITapGestureRecognizer) {
        print("Image tapped")
    }
}