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ios - 为什么UILabel TapGesture 只能在标签初始化后工作？

问题描述

我有以下代码来初始化标签：

let forgotPasswordLabel: UILabel = {
        let label = UILabel()
        label.text = "Forgot password?"
        label.font = ApplicationScheme.instance.containerScheme.typographyScheme.subtitle1
        label.textColor = ApplicationScheme.instance.containerScheme.colorScheme.onPrimaryColor
        label.textAlignment = .right
        label.sizeToFit()
        label.accessibilityRespondsToUserInteraction = true
        label.isUserInteractionEnabled = true
        label.translatesAutoresizingMaskIntoConstraints = false
        return label
    }()

后来我将它添加到子视图中：

let passwordLabel = forgotPasswordLabel
let tapGesture = UITapGestureRecognizer(target: self, action: #selector(onForgotPasswordClick))
passwordLabel.addGestureRecognizer(tapGesture)
self.view.addSubview(passwordLabel)

如果我这样做代码，那么它工作正常，但是如果我将 tapGesture 代码放在标签 forgotPasswordLabel 初始化中，则不会触发点击手势。这是为什么？

不起作用的代码：

let forgotPasswordLabel: UILabel = {
        let label = UILabel()
        label.text = "Forgot password?"
        label.font = ApplicationScheme.instance.containerScheme.typographyScheme.subtitle1
        label.textColor = ApplicationScheme.instance.containerScheme.colorScheme.onPrimaryColor
        label.textAlignment = .right
        label.sizeToFit()
        label.isUserInteractionEnabled = true
        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(onForgotPasswordClick))
        label.addGestureRecognizer(tapGesture)
        label.translatesAutoresizingMaskIntoConstraints = false
        return label
    }()

这与垃圾收集器有关吗？UILabel 无法识别的界限？或者是其他东西？

标签： iosswiftuilabelswift4uitapgesturerecognizer

解决方案

以下tapGesture代码被添加到Closure初始化程序中，并且您将目标分配为self无效。因为self这里不是ViewController 

let forgotPasswordLabel: UILabel = {
        let label = UILabel()
        label.text = "Forgot password?"
        label.font = ApplicationScheme.instance.containerScheme.typographyScheme.subtitle1
        label.textColor = ApplicationScheme.instance.containerScheme.colorScheme.onPrimaryColor
        label.textAlignment = .right
        label.sizeToFit()
        label.isUserInteractionEnabled = true
        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(onForgotPasswordClick))
        label.addGestureRecognizer(tapGesture)
        label.translatesAutoresizingMaskIntoConstraints = false
        return label
    }()

在下面的代码中，tapGesture正如预期的那样，您将目标设置self为ViewController有效的。

let forgotPasswordLabel: UILabel = {
    let label = UILabel()
    label.text = "Forgot password?"
    label.font = ApplicationScheme.instance.containerScheme.typographyScheme.subtitle1
    label.textColor = ApplicationScheme.instance.containerScheme.colorScheme.onPrimaryColor
    label.textAlignment = .right
    label.sizeToFit()
    label.accessibilityRespondsToUserInteraction = true
    label.isUserInteractionEnabled = true
    label.translatesAutoresizingMaskIntoConstraints = false
    return label
}()

let passwordLabel = forgotPasswordLabel
let tapGesture = UITapGestureRecognizer(target: self, action: #selector(onForgotPasswordClick))
passwordLabel.addGestureRecognizer(tapGesture)
self.view.addSubview(passwordLabel)

如果tapGesture您设置目标，它会告诉您在哪里寻找action手势发生的时间

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