ios - 在 UIAlertController 的文本字段中选择文本

Question

我需要在显示 UIAlertController 后立即选择文本字段的文本。但是，我在标准 UITextField 中选择文本的方式在这里不起作用。

这是我尝试过的方法，但我似乎无法让它发挥作用。

let ac = UIAlertController(title: "Rename", message: nil, preferredStyle: .Alert)
ac.addTextFieldWithConfigurationHandler({
    [] (textField: UITextField) in
    textField.selectedTextRange = textField.textRangeFromPosition(textField.beginningOfDocument, toPosition: textField.endOfDocument)
    textField.text = "filename.dat"
    })
ac.addAction(UIAlertAction(title: "CANCEL", style: .Cancel, handler: nil))
ac.addAction(UIAlertAction(title: "OK", style: .Default, handler: {
    [] Void in
    // do something
    }))
dispatch_async(dispatch_get_main_queue(), {
    self.presentViewController(ac, animated: true, completion: nil)
})

有什么想法吗？

Answer 1

我重写了你的代码。您的类应符合 UITextFieldDelegate 协议(protocol)并实现 textFieldDidBeginEditing 方法，如下所示:

class ViewController: UIViewController, UITextFieldDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()

        let ac = UIAlertController(title: "Rename", message: nil, preferredStyle: .Alert)
        ac.addTextFieldWithConfigurationHandler({
            [] (textField: UITextField) in
            textField.text = "filename.dat"
            textField.delegate = self

        })
        ac.addAction(UIAlertAction(title: "CANCEL", style: .Cancel, handler: nil))
        ac.addAction(UIAlertAction(title: "OK", style: .Default, handler: {
            [] Void in
            // do something
        }))
        dispatch_async(dispatch_get_main_queue(), {
            self.presentViewController(ac, animated: true, completion: nil)
        })

    }
    func textFieldDidBeginEditing(textField: UITextField) {
        textField.selectedTextRange = textField.textRangeFromPosition(textField.beginningOfDocument, toPosition: textField.endOfDocument)
        textField.becomeFirstResponder()
    }

}