Swift -我写了一个继承了UITextView的类，并添加了一个UILabel作为子视图作为占位符。

  import UIKit
  @IBDesignable
  class HintedTextView: UITextView {

      @IBInspectable var hintText: String = "hintText" {
          didSet{
              hintLabel.text = hintText
          }
      }

      private lazy var hintLabel: UILabel = {
          let label = UILabel()
          label.font = UIFont.systemFontOfSize(16)
          label.textColor = UIColor.lightGrayColor()
          label.translatesAutoresizingMaskIntoConstraints = false
          return label
      }()


      override init(frame: CGRect, textContainer: NSTextContainer?) {
          super.init(frame: frame, textContainer: textContainer)
          setupView()
      }

      required init?(coder aDecoder: NSCoder) {
         super.init(coder: aDecoder)
         setupView()
      }

      override func prepareForInterfaceBuilder() {
         super.prepareForInterfaceBuilder()
         setupView()
      }

      private func setupView() {

        translatesAutoresizingMaskIntoConstraints = false
        delegate = self
        font = UIFont.systemFontOfSize(16)

        addSubview(hintLabel)

        NSLayoutConstraint.activateConstraints([

           hintLabel.leftAnchor.constraintEqualToAnchor(leftAnchor, constant: 4),
           hintLabel.rightAnchor.constraintEqualToAnchor(rightAnchor, constant: 8),
           hintLabel.topAnchor.constraintEqualToAnchor(topAnchor, constant: 4),
           hintLabel.heightAnchor.constraintEqualToConstant(30)
         ])
        }

      override func layoutSubviews() {
        super.layoutSubviews()
        setupView()
     }

}

这是我准备使用的解决方案，如果您正在处理多个文本视图

func textViewShouldBeginEditing(textView: UITextView) -> Bool {        
    // Set cursor to the beginning if placeholder is set
    if textView.textColor == UIColor.lightGrayColor() {
        textView.selectedTextRange = textView.textRangeFromPosition(textView.beginningOfDocument, toPosition: textView.beginningOfDocument)
    }

    return true
}

func textView(textView: UITextView, shouldChangeTextInRange range: NSRange, replacementText text: String) -> Bool {
    // Remove placeholder
    if textView.textColor == UIColor.lightGrayColor() && text.characters.count > 0 {
        textView.text = ""
        textView.textColor = UIColor.blackColor()
    }

    if text == "\n" {
        textView.resignFirstResponder()
        return false
    }

    return true
}

func textViewDidChange(textView: UITextView) {
    // Set placeholder if text is empty
    if textView.text.isEmpty {
        textView.text = NSLocalizedString("Hint", comment: "hint")
        textView.textColor = UIColor.lightGrayColor()
        textView.selectedTextRange = textView.textRangeFromPosition(textView.beginningOfDocument, toPosition: textView.beginningOfDocument)
    }
}

func textViewDidChangeSelection(textView: UITextView) {
    // Set cursor to the beginning if placeholder is set
    let firstPosition = textView.textRangeFromPosition(textView.beginningOfDocument, toPosition: textView.beginningOfDocument)

    // Do not change position recursively
    if textView.textColor == UIColor.lightGrayColor() && textView.selectedTextRange != firstPosition {
        textView.selectedTextRange = firstPosition
    }
}

我们的解决方案避免了与UITextView文本和textColor属性的混淆，如果您要维护字符计数器，这是非常方便的。

很简单:

1)在Storyboard中创建一个与主UITextView属性相同的虚拟UITextView。将占位符文本分配给虚拟文本。

2)对齐两个uitextview的上、左、右边缘。

3)把假人放在主人的后面。

4)重写master的textViewDidChange(textView:)委托函数，如果master有0个字符，则显示dummy。否则，显示master。

这假设两个uitextview的背景都是透明的。如果没有，当有0个字符时，将假人放在上面，当有>个0个字符时，将它推到下面。您还必须交换响应器，以确保光标跟随正确的UITextView。

这里有一些东西可以被放到UIStackView中，它会使用内部高度约束来调整自己的大小。可能需要调整以适应特定的需求。

import UIKit

public protocol PlaceholderTextViewDelegate: class {
  func placeholderTextViewTextChanged(_ textView: PlaceholderTextView, text: String)
}

public class PlaceholderTextView: UIView {

  public weak var delegate: PlaceholderTextViewDelegate?
  private var heightConstraint: NSLayoutConstraint?

  public override init(frame: CGRect) {
    self.allowsNewLines = true

    super.init(frame: frame)

    self.heightConstraint = self.heightAnchor.constraint(equalToConstant: 0)
    self.heightConstraint?.isActive = true

    self.addSubview(self.placeholderTextView)
    self.addSubview(self.textView)

    self.pinToCorners(self.placeholderTextView)
    self.pinToCorners(self.textView)

    self.updateHeight()
  }

  public override func didMoveToSuperview() {
    super.didMoveToSuperview()

    self.updateHeight()
  }

  private func pinToCorners(_ view: UIView) {
    NSLayoutConstraint.activate([
      view.leadingAnchor.constraint(equalTo: self.leadingAnchor),
      view.trailingAnchor.constraint(equalTo: self.trailingAnchor),
      view.topAnchor.constraint(equalTo: self.topAnchor),
      view.bottomAnchor.constraint(equalTo: self.bottomAnchor)
    ])
  }

  // Accessors
  public var text: String? {
    didSet {
      self.textView.text = text
      self.textViewDidChange(self.textView)
      self.updateHeight()
    }
  }

  public var textColor: UIColor? {
    didSet {
      self.textView.textColor = textColor
      self.updateHeight()
    }
  }

  public var font: UIFont? {
    didSet {
      self.textView.font = font
      self.placeholderTextView.font = font
      self.updateHeight()
    }
  }

  public override var tintColor: UIColor? {
    didSet {
      self.textView.tintColor = tintColor
      self.placeholderTextView.tintColor = tintColor
    }
  }

  public var placeholderText: String? {
    didSet {
      self.placeholderTextView.text = placeholderText
      self.updateHeight()
    }
  }

  public var placeholderTextColor: UIColor? {
    didSet {
      self.placeholderTextView.textColor = placeholderTextColor
      self.updateHeight()
    }
  }

  public var allowsNewLines: Bool

  public required init?(coder _: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }

  private lazy var textView: UITextView = self.newTextView()
  private lazy var placeholderTextView: UITextView = self.newTextView()

  private func newTextView() -> UITextView {
    let textView = UITextView()
    textView.translatesAutoresizingMaskIntoConstraints = false
    textView.isScrollEnabled = false
    textView.delegate = self
    textView.backgroundColor = .clear
    return textView
  }

  private func updateHeight() {
    let maxSize = CGSize(width: self.frame.size.width, height: .greatestFiniteMagnitude)

    let textViewSize = self.textView.sizeThatFits(maxSize)
    let placeholderSize = self.placeholderTextView.sizeThatFits(maxSize)

    let maxHeight = ceil(CGFloat.maximum(textViewSize.height, placeholderSize.height))

    self.heightConstraint?.constant = maxHeight
  }
}

extension PlaceholderTextView: UITextViewDelegate {
  public func textViewDidChangeSelection(_: UITextView) {
    self.placeholderTextView.alpha = self.textView.text.isEmpty ? 1 : 0
    self.updateHeight()
  }

  public func textViewDidChange(_: UITextView) {
    self.delegate?.placeholderTextViewTextChanged(self, text: self.textView.text)
  }

  public func textView(_: UITextView, shouldChangeTextIn _: NSRange,
                       replacementText text: String) -> Bool {
    let containsNewLines = text.rangeOfCharacter(from: .newlines)?.isEmpty == .some(false)
    guard !containsNewLines || self.allowsNewLines else { return false }

    return true
  }
}

这就是我所做的。倾向于代码清晰和简单。我需要添加一个textView，将获得一些额外的笔记在我的应用程序。这额外的笔记可以创建或保存后修改。见下文。HTH。：）

class NotesTextView: UITextView {

    var placeholder = "" {
        didSet {
            showPlaceholder()
        }
    }
    
    // if the text is the placeholder, then assign a color fitting for a
    // placeholder text, else, assign it your color of choice.
    override var text: String! {
        didSet {
            textColor = text == placeholder ? .tertiaryLabel : .systemBlue
        }
    }
    
    
    override init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame, textContainer: textContainer)
        
        delegate = self
        //config your font and translateAutoResizingMaskIntoConstraints here
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    private func showPlaceholder() {
        text = placeholder
    }
    
    private func hidePlaceholder() {
        text = ""
    }
}

extension NotesTextView: UITextViewDelegate {
    func textViewDidBeginEditing(_ textView: UITextView) {
        if text == placeholder {
            hidePlaceholder()
        }
    }
    
    func textViewDidEndEditing(_ textView: UITextView) {
        if text.isEmpty {
            showPlaceholder()
        }
    }
}

有我的简单版本的UITextView与占位符。主要思想是:

隐藏占位符，如果用户开始编辑和占位符是可见的 如果用户结束编辑并且文本视图的文本为空，则显示占位符。

class PlaceholderTextView: UITextView {

    var placeholder = "" {
        didSet {
            if isPlaceholderVisible {
                showPlaceholder()
            }
        }
    }

    var isPlaceholderVisible = true {
        didSet {
            isPlaceholderVisible ? showPlaceholder() : hidePlaceholder()
        }
    }

    init() {
        super.init(frame: .zero, textContainer: nil)
        delegate = self
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    private func showPlaceholder() {
        text = placeholder
        // Set other things like color of text for placeholder, ...
    }

    private func hidePlaceholder() {
        text = ""
        // Set other things like color of text for normal input, ...
    }

}

extension PlaceholderTextView: UITextViewDelegate {
    func textViewDidBeginEditing(_ textView: UITextView) {
        if isPlaceholderVisible {
            isPlaceholderVisible = false
        }
    }

    func textViewDidEndEditing(_ textView: UITextView) {
        if text.isEmpty {
            isPlaceholderVisible = true
        }
    }
}