ios - 如何使用自动布局在 subview 中创建 UIGestureRecognizer？

Question

当我尝试在 subview 中使用 UIGestureRecognizer 时，其框架是通过 superviewcontroller 中的自动布局指定的，它不会响应手势。我相信这是因为手势识别器不知道 View 的真实尺寸，正如自动布局约束所描述的那样。这怎么能解决？这是我的代码:

import UIKit
class MyLabel: UILabel {
    var delegate: MyProtocolForSwipeRecognition!
    var gestureRecognizer: UISwipeGestureRecognizer
    init() {
        gestureRecognizer = UISwipeGestureRecognizer(target: delegate, action: "swiped")
        super.init(frame: CGRect()) //<- I believe my problem is because it thinks
        //the frame is this empty CGRect, but I don't know what else to put here.
        translatesAutoresizingMaskIntoConstraints = false
        addGestureRecognizer(gestureRecognizer)
    }
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

提前致谢。

Answer 1

您的方法有两个问题(自动布局不是问题):

1. 您必须在您的 MyLabel 类上设置 userInteractionEnabled = true
2. 添加手势识别器时，必须确保 delegate 不为 nil。您可以通过添加一个将委托(delegate)作为参数的初始化程序来做到这一点

这是让它工作的方法(无需保留对手势识别器的引用):

class MyLabel: UILabel {
    var delegate: MyProtocolForSwipeRecognition

    init(withDelegate delegate: MyProtocolForSwipeRecognition) {
        self.delegate = delegate
        let gestureRecognizer = UISwipeGestureRecognizer(target: delegate, action: "swiped")
        super.init(frame: CGRectZero)
        addGestureRecognizer(gestureRecognizer)
        userInteractionEnabled = true
    }
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

然后你可以在实现你的协议(protocol)的类中初始化你的标签:

let label = MyLabel(withDelegate: self)