如何在应用加载时选择文字？

Question

标题真的说明了一切。我尝试过以下方式从viewDidLoad中选择文字：

override func viewDidLoad() {
    ...
    guessField.text = "    "

    guessField.becomeFirstResponder()
    guessField.selectedTextRange = guessField.textRange(from: guessField.beginningOfDocument, to: guessField.position(from: guessField.endOfDocument, offset: -3)!)

}

但是，这不起作用;光标刚出现在最后一个位置。有没有人有想法解决这个问题？

Answer 1

一旦您的视图加载，看起来需要一些时间。尝试以下解决方案：

首先在你的课程中添加以下功能：

func delayWithSeconds(_ seconds: Double, completion: @escaping () -> ()) {
    DispatchQueue.main.asyncAfter(deadline: .now() + seconds) {
        completion()
    }
}

然后在viewWillAppear方法中使用它，如下所示：

override func viewWillAppear(_ animated: Bool) {

    delayWithSeconds(1) {
        self.guessField.text = "    "

        self.guessField.becomeFirstResponder()
        self.guessField.selectedTextRange = self.guessField.textRange(from: self.guessField.beginningOfDocument, to: self.guessField.position(from: self.guessField.endOfDocument, offset: -3)!)
    }
}

我刚把它推迟了1秒。