基于这里已经给出的一些很好的建议，我能够将以下轻量级的、与接口生成器兼容的UITextView子类组合在一起，它是:

包括可配置的占位符文本，样式就像UITextField一样。 不需要任何额外的子视图或约束。 不需要来自ViewController的任何委托或其他行为。 不需要任何通知。 保持占位符文本与查看字段文本属性的任何外部类完全分离。

任何改进建议都是受欢迎的，特别是如果有任何方法通过编程来获取iOS的占位符颜色，而不是硬编码它。

斯威夫特v5:

import UIKit
@IBDesignable class TextViewWithPlaceholder: UITextView {
    
    override var text: String! { // Ensures that the placeholder text is never returned as the field's text
        get {
            if showingPlaceholder {
                return "" // When showing the placeholder, there's no real text to return
            } else { return super.text }
        }
        set { super.text = newValue }
    }
    @IBInspectable var placeholderText: String = ""
    @IBInspectable var placeholderTextColor: UIColor = UIColor(red: 0.78, green: 0.78, blue: 0.80, alpha: 1.0) // Standard iOS placeholder color (#C7C7CD). See https://stackoverflow.com/questions/31057746/whats-the-default-color-for-placeholder-text-in-uitextfield
    private var showingPlaceholder: Bool = true // Keeps track of whether the field is currently showing a placeholder
    
    override func didMoveToWindow() {
        super.didMoveToWindow()
        if text.isEmpty {
            showPlaceholderText() // Load up the placeholder text when first appearing, but not if coming back to a view where text was already entered
        }
    }
    
    override func becomeFirstResponder() -> Bool {
        // If the current text is the placeholder, remove it
        if showingPlaceholder {
            text = nil
            textColor = nil // Put the text back to the default, unmodified color
            showingPlaceholder = false
        }
        return super.becomeFirstResponder()
    }
    
    override func resignFirstResponder() -> Bool {
        // If there's no text, put the placeholder back
        if text.isEmpty {
            showPlaceholderText()
        }
        return super.resignFirstResponder()
    }
    
    private func showPlaceholderText() {
        showingPlaceholder = true
        textColor = placeholderTextColor
        text = placeholderText
    }
}

迅速:

以编程方式或通过Interface Builder添加你的文本视图，如果是最后一个，创建outlet:

@IBOutlet weak var yourTextView: UITextView!

请添加委托(UITextViewDelegate):

class ViewController: UIViewController, UITextViewDelegate {

在viewDidLoad方法中，添加如下内容:

override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

    yourTextView.delegate = self
    yourTextView.text = "Placeholder text goes right here..."
    yourTextView.textColor = UIColor.lightGray

现在让我来介绍一下神奇的部分，添加这个函数:

func textViewDidBeginEditing(_ textView: UITextView) {

    if yourTextView.textColor == UIColor.lightGray {
        yourTextView.text = ""
        yourTextView.textColor = UIColor.black
    }
}

请注意，这将在编辑开始时执行，在那里我们将检查条件来告知状态，使用color属性。 设置文本为nil我不建议。在此之后，我们将文本颜色设置为所需的颜色，在本例中为黑色。

现在也添加这个函数:

func textViewDidEndEditing(_ textView: UITextView) {

    if yourTextView.text == "" {

        yourTextView.text = "Placeholder text ..."
        yourTextView.textColor = UIColor.lightGray
    }
}

让我坚持一下，不要与零进行比较，我已经试过了，它不会起作用。然后我们将值设置回占位符样式，并将颜色设置回占位符颜色，因为这是在textViewDidBeginEditing中检查的条件。

浮动的占位符

将占位符标签放置在文本视图之上，通过跟踪文本视图字符计数的变化来设置其字体、颜色和管理占位符可见性，这是简单、安全且可靠的。

斯威夫特5:

class NotesViewController : UIViewController {

    @IBOutlet var textView : UITextView!
    var placeholderLabel : UILabel!
        
    override func viewDidLoad() {
        super.viewDidLoad()
    
        textView.delegate = self
        placeholderLabel = UILabel()
        placeholderLabel.text = "Enter some text..."
        placeholderLabel.font = .italicSystemFont(ofSize: (textView.font?.pointSize)!)
        placeholderLabel.sizeToFit()
        textView.addSubview(placeholderLabel)
        placeholderLabel.frame.origin = CGPoint(x: 5, y: (textView.font?.pointSize)! / 2)
        placeholderLabel.textColor = .tertiaryLabel
        placeholderLabel.isHidden = !textView.text.isEmpty
    }
}

extension NotesViewController : UITextViewDelegate {
    func textViewDidChange(_ textView: UITextView) {
        placeholderLabel.isHidden = !textView.text.isEmpty
    }
}

迅速:

添加你的TextView @IBOutlet:

@IBOutlet weak var txtViewMessage: UITextView!

在viewWillAppear方法中，添加以下内容:

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    txtViewMessage.delegate = self    // Give TextViewMessage delegate Method
    
    txtViewMessage.text = "Place Holder Name"
    txtViewMessage.textColor = UIColor.lightGray
}

请添加委托使用扩展(UITextViewDelegate):

// MARK: - UITextViewDelegate
extension ViewController: UITextViewDelegate {

    func textViewDidBeginEditing(_ textView: UITextView) {

        if !txtViewMessage.text!.isEmpty && txtViewMessage.text! == "Place Holder Name" {
            txtViewMessage.text = ""
            txtViewMessage.textColor = UIColor.black
        }
    }

    func textViewDidEndEditing(_ textView: UITextView) {
    
        if txtViewMessage.text.isEmpty {
            txtViewMessage.text = "Place Holder Name"
            txtViewMessage.textColor = UIColor.lightGray
        }
    }
}

迅速的回答

这是一个自定义类，用于动画占位符。

class CustomTextView: UITextView {
    
    //   MARK: - public
    
    public var placeHolderText: String? = "Enter Reason.."
    
    public lazy var placeHolderLabel: UILabel! = {
        let placeHolderLabel = UILabel(frame: .zero)
        placeHolderLabel.numberOfLines = 0
        placeHolderLabel.backgroundColor = .clear
        placeHolderLabel.alpha = 0.5
        return placeHolderLabel
    }()
    
    //   MARK: - Init
    
    override init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame, textContainer: textContainer)
        enableNotifications()
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        enableNotifications()
    }
    
    func setup() {
        placeHolderLabel.frame = CGRect(x: 8, y: 8, width: self.bounds.size.width - 16, height: 15)
        placeHolderLabel.sizeToFit()
    }
    
    //   MARK: - Cycle
    
    override func awakeFromNib() {
        super.awakeFromNib()
        
        textContainerInset = UIEdgeInsets(top: 8, left: 5, bottom: 8, right: 8)
        returnKeyType = .done
        addSubview(placeHolderLabel)
        placeHolderLabel.frame = CGRect(x: 8, y: 8, width: self.bounds.size.width - 16, height: 15)
        placeHolderLabel.textColor = textColor
        placeHolderLabel.font = font
        placeHolderLabel.text = placeHolderText
        bringSubviewToFront(placeHolderLabel)
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()
        setup()
    }
    
    //   MARK: - Notifications
    
    private func enableNotifications() {
        NotificationCenter.default.addObserver(self, selector: #selector(textDidChangeNotification(_:)), name: UITextView.textDidChangeNotification , object: nil)
    }
    
    @objc func textDidChangeNotification(_ notify: Notification) {
        guard self == notify.object as? UITextView else { return }
        guard placeHolderText != nil else { return }
        
        UIView.animate(withDuration: 0.25, animations: {
            self.placeHolderLabel.alpha = (self.text.count == 0) ? 0.5 : 0
        }, completion: nil)
    }
    
}

func setPlaceholder(){ var placeholderLabel = UILabel() placeholderLabel.text = "Describe your need..." placeholderLabel.font = UIFont.init(name: "Lato-Regular", size: 15.0) ?? UIFont.boldSystemFont(ofSize: 14.0) placeholderLabel.sizeToFit() descriptionTextView.addSubview(placeholderLabel) placeholderLabel.frame.origin = CGPoint(x: 5, y: (descriptionTextView.font?.pointSize)! / 2) placeholderLabel.textColor = UIColor.lightGray placeholderLabel.isHidden = !descriptionTextView.text.isEmpty } //Delegate Method. func textViewDidChange(_ textView: UITextView) { placeholderLabel.isHidden = !textView.text.isEmpty }