UIAlertController 的文本字段委托不会被调用 [英] UIAlertController's textfield delegate does not get called

问题描述

我已经向 UIAlertController 添加了一个 UITextField，但是 shouldChangeCharactersInRange 不会被触发.为什么?我设置了委托.

I have added a UITextField to UIAlertController, but shouldChangeCharactersInRange will get not fired. Why? I set the delegate.

let alertController = UIAlertController(title: "", message: "xxx", preferredStyle: .Alert)

self.presentViewController(alertController, animated:true, completion:nil)
let textField = UITextField()
textField.delegate = self
alertController.addTextFieldWithConfigurationHandler(nil)

在同一个类中，委托:

func textField(textField: UITextField!,
    shouldChangeCharactersInRange range: NSRange,
    replacementString string: String!) -> Bool {

推荐答案

您为其设置委托的文本字段与添加到警报控制器的文本字段不同.基本上，您正在创建 UITextField 的新实例，但从未为其提供框架或将其添加到视图层次结构中.同时，您使用 addTextFieldWithConfigurationHandler() 将文本字段添加到警报控制器，但您从未为此文本字段设置委托.我相信这就是你想要的:

The text field that you're setting the delegate for is not the same text field that is added to the alert controller. Basically, you're creating a new instance of UITextField, but never giving it a frame, or adding it to the view hierarchy. At the same time, you're using addTextFieldWithConfigurationHandler() to add a text field to the alert controller, but you never set the delegate for this text field. I believe this is what you want:

let alertController = UIAlertController(title: "", message: "xxx", preferredStyle: .Alert)

alertController.addTextFieldWithConfigurationHandler {[weak self] (textField: UITextField!) in
    textField.delegate = self
}

self.presentViewController(alertController, animated:true, completion:nil)

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