swift - UITextView 未触发委托(delegate)协议(protocol)函数

Question

我有一个快速文件，我试图在其中创建一个自定义类来处理一页上多个 TextView 的占位符。我更喜欢一个单独的类，因为我认为处理多个 View 更干净。问题是，当这些事件发生时，函数 textViewDidEndEditing 和 textViewDidBeginEditing 不会被调用。

我已经通过将 PostPage 设置为委托(delegate)成功地工作了，但我不知道如何使用多个 UITextView 来做到这一点。

这是我的代码:

import UIKit

class PostPage: UIViewController, UITextViewDelegate {

    @IBOutlet weak var eventDescription: UITextView!
    @IBOutlet weak var eventTitle: UITextView!

    var placeholderShowing = true

    override func viewDidLoad() {
        super.viewDidLoad()

        // Add a placeholder for the text
        let ph_descr = PlaceHolderHandler(placeholderText: "Description", textBox: eventDescription)
        eventDescription.delegate = ph_descr

        let ph_title = PlaceHolderHandler(placeholderText: "Title", textBox: eventTitle)
        eventTitle.delegate = ph_title
    }

}

 class PlaceHolderHandler: NSObject, UITextViewDelegate {

    var placeholderShowing = true
    var placeholderText = ""

    required init(placeholderText: String, textBox: UITextView) {
        super.init()
        self.placeholderText = placeholderText
        textBox.text = placeholderText
        textBox.textColor = UIColor.lightGray
    }


    // MARK:- UITextViewDelegates

    public func textViewDidBeginEditing(_ textView: UITextView) {
        if self.placeholderShowing {
            textView.text = ""
            textView.textColor = UIColor.black
            self.placeholderShowing = false
        }

    }

    public func textViewDidEndEditing(_ textView: UITextView) {
        if textView.text == "" {
            textView.text = "Description"
            textView.textColor = UIColor.lightGray
            self.placeholderShowing = true
        }
    }
 }

当我选择任一 UITextView 时，我希望调用相应的函数，并相应地调整文本。

Answer 1

您需要保留 phDescr 和 phTitle，因为在您的代码中它们是局部变量，因此在 viewDidLoad 结束时取消分配

>

import UIKit

class PostPage: UIViewController, UITextViewDelegate {

    @IBOutlet weak var eventDescription: UITextView!
    @IBOutlet weak var eventTitle: UITextView!

    var placeholderShowing = true

    var phDescr, phTitle:PlaceHolderHandler!

    override func viewDidLoad() {
        super.viewDidLoad()

        // Add a placeholder for the text
        phDescr = PlaceHolderHandler(placeholderText: "Description", textBox: eventDescription)
        eventDescription.delegate = phDescr

        phTitle = PlaceHolderHandler(placeholderText: "Title", textBox: eventTitle)
        eventTitle.delegate = phTitle
    }

}

也使用驼峰命名法来命名变量

I've had it successfully work by setting the PostPage to the delegate, but I don't see how I could do that with multiple UITextView

当然，您可以将两者的委托(delegate)设置为 PostPage 并了解哪一个是完整的使用

func textViewDidBeginEditing(_ textView: UITextView) {
   if textView == eventDescription {
   }
   else {  // eventTitle
   }
}