可能是UITextView占位符实现的最简单的开箱即用的解决方案，不会遭受:

使用UILabel而不是UITextView，这可能会有不同的表现 切换到和从占位符“UITextView”拷贝，将捕获第一个键入的字符将从主UITextView控件丢失 打乱主UITextView控件的文本内容，将占位符替换为空字符串或第一个键入的字符。边界情况是，如果用户输入占位符文本，一些建议的实现将把它作为一个占位符本身。

斯威夫特5:

import UIKit
import SnapKit
import RxSwift
import RxCocoa

class TextAreaView: UIView {
    let textArea = UITextView()
    let textAreaPlaceholder = UITextView()
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        commonSetup()
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        commonSetup()
    }
    
    private func commonSetup() {
        
        addSubview(textAreaPlaceholder)
        addSubview(textArea)
        
        textArea.isScrollEnabled = false
        textArea.delegate = self

        textAreaPlaceholder.isScrollEnabled = false
        textAreaPlaceholder.textColor = UIColor.lightGray
        
        textArea.snp.makeConstraints { make in
            make.top.bottom.leading.trailing.equalToSuperview()
        }

        textAreaPlaceholder.snp.makeConstraints { make in
            make.top.bottom.leading.trailing.equalTo(textArea.snp.top)
        }

        textAreaPlaceholder.text = "Placeholder"
        
        updatePlaceholder()
    }
    
    func updatePlaceholder() {
        if textArea.text.count > 0 {
            textArea.alpha = 1.0
        } else {
            textArea.alpha = 0.0
        }
    }
}

extension TextAreaView: UITextViewDelegate {
    func textViewDidChange(_ textView: UITextView) {
        updatePlaceholder()
    }
}

我喜欢@nerdist的解决方案。在此基础上，我创建了UITextView的扩展:

import Foundation
import UIKit

extension UITextView
{
  private func add(_ placeholder: UILabel) {
    for view in self.subviews {
        if let lbl = view as? UILabel  {
            if lbl.text == placeholder.text {
                lbl.removeFromSuperview()
            }
        }
    }
    self.addSubview(placeholder)
  }

  func addPlaceholder(_ placeholder: UILabel?) {
    if let ph = placeholder {
      ph.numberOfLines = 0  // support for multiple lines
      ph.font = UIFont.italicSystemFont(ofSize: (self.font?.pointSize)!)
      ph.sizeToFit()
      self.add(ph)
      ph.frame.origin = CGPoint(x: 5, y: (self.font?.pointSize)! / 2)
      ph.textColor = UIColor(white: 0, alpha: 0.3)
      updateVisibility(ph)
    }
  }

  func updateVisibility(_ placeHolder: UILabel?) {
    if let ph = placeHolder {
      ph.isHidden = !self.text.isEmpty
    }
  }
}

例如，在ViewController类中，我是这样使用它的:

class MyViewController: UIViewController, UITextViewDelegate {
  private var notePlaceholder: UILabel!
  @IBOutlet weak var txtNote: UITextView!
  ...
  // UIViewController
  override func viewDidLoad() {
    notePlaceholder = UILabel()
    notePlaceholder.text = "title\nsubtitle\nmore..."
    txtNote.addPlaceholder(notePlaceholder)
    ...
  }

  // UITextViewDelegate
  func textViewDidChange(_ textView: UITextView) {
    txtNote.updateVisbility(notePlaceholder)
    ...
  }

UITextview的占位符!

更新:

如果你在代码中改变textview的文本，记得调用updateVisibitly方法来隐藏占位符:

txtNote.text = "something in code"
txtNote.updateVisibility(self.notePlaceholder) // hide placeholder if text is not empty.

为了防止占位符被添加多次，在扩展中添加了一个私有add()函数。

var placeholderLabel : UILabel!
  textviewDescription.delegate = self
    placeholderLabel = UILabel()
    placeholderLabel.text = "Add a description"

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

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
    }
}

我不知道为什么人们会把这个问题复杂化....这是相当直接和简单的。下面是UITextView的一个子类，它提供了所请求的功能。

- (void)customInit
{
    self.contentMode = UIViewContentModeRedraw;
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];
}

    - (void)textChanged:(NSNotification *)notification
    {
        if (notification.object == self) {
            if(self.textStorage.length != 0 || !self.textStorage.length) {
                [self setNeedsDisplay];
            }
        }
    }


    #pragma mark - Setters

    - (void)setPlaceholderText:(NSString *)placeholderText withFont:(UIFont *)font
    {
        self.placeholderText = placeholderText;
        self.placeholderTextFont = font;

    }



    - (void)drawRect:(CGRect)rect
    {
        [super drawRect:rect];
        [[UIColor lightGrayColor] setFill];

        if (self.textStorage.length != 0) {
            return;
        }

        CGRect inset = CGRectInset(rect, 8, 8);//Default rect insets for textView
        NSDictionary *attributes =  @{NSFontAttributeName: self.placeholderTextFont, NSForegroundColorAttributeName: [UIColor grayColor]};
        [self.placeholderText drawInRect:inset withAttributes:attributes];
    }`

Swift 4、4.2和5

[![@IBOutlet var detailTextView: UITextView!

override func viewDidLoad() {
        super.viewDidLoad()
        detailTextView.delegate = self
}

extension ContactUsViewController : UITextViewDelegate {

    public func textViewDidBeginEditing(_ textView: UITextView) {
        if textView.text == "Write your message here..." {
            detailTextView.text = ""
            detailTextView.textColor = UIColor.init(red: 0/255, green: 0/255, blue: 0/255, alpha: 0.86)

        }
        textView.becomeFirstResponder()
    }

    public func textViewDidEndEditing(_ textView: UITextView) {

        if textView.text == "" {
            detailTextView.text = "Write your message here..."
            detailTextView.textColor = UIColor.init(red: 0/255, green: 0/255, blue: 0/255, alpha: 0.30)
        }
        textView.resignFirstResponder()
    }
[![}][1]][1]