Question

按下按钮后，我在小时候添加了SecondViewController。下面的代码是MainViewController内的按钮操作。

@IBAction func btnPressed(_ sender: Any) {    
    addChildViewController(SecondViewController())

    view.superview?.addSubview(SecondViewController().view)

    SecondViewController().view.frame = (view.superview?.bounds)!
                SecondViewController().view.autoresizingMask = [.flexibleWidth, .flexibleHeight]

    SecondViewController().didMove(toParentViewController: self)
}

在SecondViewController内，我像这样设置UITextFieldDelegate

class SecondViewController: UIViewController, UITextFieldDelegate {

我在我的xib上设置了带有视图控制器的textField委托。甚至尝试myTextField.delegate = self。这是我的shouldChangeCharactersIn range

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        print("While entering the characters this method gets called")
        return true;
    }

但是这种方法永远不会被调用。

Answer 1

您正在做的是创建SecondViewController的5个不同实例 - 您通过在每行中调用初始化程序（SecondViewController()）来实现此目的

@IBAction func btnPressed(_ sender: Any) {    
    addChildViewController(SecondViewController()) // first instance created

    view.superview?.addSubview(SecondViewController().view) // second instance created

    SecondViewController().view.frame = (view.superview?.bounds)! // third instance created
    SecondViewController().view.autoresizingMask = [.flexibleWidth, .flexibleHeight] // fourth instance created

    SecondViewController().didMove(toParentViewController: self) // fifth instance created
}

改为

@IBAction func btnPressed(_ sender: Any) {   
    let secondViewController = SecondViewController()

    addChildViewController(secondViewController)
    view.superview?.addSubview(secondViewController.view)
    secondViewController.view.frame = (view.superview?.bounds)!
    secondViewController.view.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    secondViewController.didMove(toParentViewController: self)
}

UITextFieldDelegate不适用于childViewController Swift

1 个答案: