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。

斯威夫特3.1

这个扩展为我工作得很好:https://github.com/devxoul/UITextView-Placeholder

下面是一个代码片段:

通过pod安装:

pod 'UITextView+Placeholder', '~> 1.2'

将它导入到类中

import UITextView_Placeholder

并添加占位符属性到您已经创建的UITextView

textView.placeholder = "Put some detail"

这是…… 这里是它的外观(第三个框是一个UITextView)

Swift 4更新

UITextView本身没有占位符属性，所以你必须用UITextViewDelegate方法来创建和操作一个。我建议使用下面的解决方案#1或#2，这取决于所需的行为。

注意:对于任何一种解决方案，都需要将UITextViewDelegate添加到类中，并设置textView.delegate = self来使用文本视图的委托方法。

解决方案#1 -如果你想让占位符在用户选择文本视图时立即消失:

首先将UITextView设置为包含占位符文本，并将其设置为浅灰色，以模拟UITextField的占位符文本的外观。要么在viewDidLoad中这样做，要么在文本视图创建时这样做。

textView.text = "Placeholder"
textView.textColor = UIColor.lightGray

然后，当用户开始编辑文本视图时，如果文本视图包含一个占位符(即，如果其文本颜色是浅灰色)，则清除占位符文本，并将文本颜色设置为黑色，以便容纳用户的输入。

func textViewDidBeginEditing(_ textView: UITextView) {
    if textView.textColor == UIColor.lightGray {
        textView.text = nil
        textView.textColor = UIColor.black
    }
}

然后，当用户完成编辑文本视图并将其作为第一响应器时，如果文本视图为空，则通过重新添加占位符文本并将其颜色设置为浅灰色来重置其占位符。

func textViewDidEndEditing(_ textView: UITextView) {
    if textView.text.isEmpty {
        textView.text = "Placeholder"
        textView.textColor = UIColor.lightGray
    }
}

解决方案#2 -如果你想要占位符显示文本视图是空的，即使文本视图被选中:

首先在viewDidLoad中设置占位符:

textView.text = "Placeholder"
textView.textColor = UIColor.lightGray

textView.becomeFirstResponder()

textView.selectedTextRange = textView.textRange(from: textView.beginningOfDocument, to: textView.beginningOfDocument)

(注意:由于OP希望在视图加载时立即选择文本视图，所以我将文本视图选择合并到上面的代码中。如果这不是你想要的行为，你不希望在视图加载时选择文本视图，从上面的代码块中删除最后两行。)

然后使用shouldChangeTextInRange UITextViewDelegate方法，如下所示:

func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {

    // Combine the textView text and the replacement text to
    // create the updated text string
    let currentText:String = textView.text
    let updatedText = (currentText as NSString).replacingCharacters(in: range, with: text)

    // If updated text view will be empty, add the placeholder
    // and set the cursor to the beginning of the text view
    if updatedText.isEmpty {

        textView.text = "Placeholder"
        textView.textColor = UIColor.lightGray

        textView.selectedTextRange = textView.textRange(from: textView.beginningOfDocument, to: textView.beginningOfDocument)
    }

    // Else if the text view's placeholder is showing and the
    // length of the replacement string is greater than 0, set 
    // the text color to black then set its text to the
    // replacement string
     else if textView.textColor == UIColor.lightGray && !text.isEmpty {
        textView.textColor = UIColor.black
        textView.text = text
    }

    // For every other case, the text should change with the usual
    // behavior...
    else {
        return true
    }

    // ...otherwise return false since the updates have already
    // been made
    return false
}

也实现textViewDidChangeSelection，以防止用户改变光标的位置，而占位符是可见的。(注意:textViewDidChangeSelection在视图加载之前被调用，所以如果窗口是可见的，只检查文本视图的颜色):

func textViewDidChangeSelection(_ textView: UITextView) {
    if self.view.window != nil {
        if textView.textColor == UIColor.lightGray {
            textView.selectedTextRange = textView.textRange(from: textView.beginningOfDocument, to: textView.beginningOfDocument)
        }
    }
}

我相信这是一个非常干净的解决方案。它在实际文本视图下面添加了一个虚拟文本视图，并根据实际文本视图中的文本显示或隐藏它:

import Foundation
import UIKit

class TextViewWithPlaceholder: UITextView {

    private var placeholderTextView: UITextView = UITextView()

    var placeholder: String? {
        didSet {
            placeholderTextView.text = placeholder
        }
    }

    override var text: String! {
        didSet {
            placeholderTextView.isHidden = text.isEmpty == false
        }
    }

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

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

    private func commonInit() {
        applyCommonTextViewAttributes(to: self)
        configureMainTextView()
        addPlaceholderTextView()
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(textDidChange),
                                               name: UITextView.textDidChangeNotification,
                                               object: nil)
    }

    func addPlaceholderTextView() {
        applyCommonTextViewAttributes(to: placeholderTextView)
        configurePlaceholderTextView()
        insertSubview(placeholderTextView, at: 0)
    }

    private func applyCommonTextViewAttributes(to textView: UITextView) {
        textView.translatesAutoresizingMaskIntoConstraints = false
        textView.textContainer.lineFragmentPadding = 0
        textView.textContainerInset = UIEdgeInsets(top: 10,
                                                   left: 10,
                                                   bottom: 10,
                                                   right: 10)
    }

    private func configureMainTextView() {
        // Do any configuration of the actual text view here
    }

    private func configurePlaceholderTextView() {
        placeholderTextView.text = placeholder
        placeholderTextView.font = font
        placeholderTextView.textColor = UIColor.lightGray
        placeholderTextView.frame = bounds
        placeholderTextView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        placeholderTextView.frame = bounds
    }

    @objc func textDidChange() {
        placeholderTextView.isHidden = !text.isEmpty
    }

}

在swift2.2:

public class CustomTextView: UITextView {

private struct Constants {
    static let defaultiOSPlaceholderColor = UIColor(red: 0.0, green: 0.0, blue: 0.0980392, alpha: 0.22)
}
private let placeholderLabel: UILabel = UILabel()

private var placeholderLabelConstraints = [NSLayoutConstraint]()

@IBInspectable public var placeholder: String = "" {
    didSet {
        placeholderLabel.text = placeholder
    }
}

@IBInspectable public var placeholderColor: UIColor = CustomTextView.Constants.defaultiOSPlaceholderColor {
    didSet {
        placeholderLabel.textColor = placeholderColor
    }
}

override public var font: UIFont! {
    didSet {
        placeholderLabel.font = font
    }
}

override public var textAlignment: NSTextAlignment {
    didSet {
        placeholderLabel.textAlignment = textAlignment
    }
}

override public var text: String! {
    didSet {
        textDidChange()
    }
}

override public var attributedText: NSAttributedString! {
    didSet {
        textDidChange()
    }
}

override public var textContainerInset: UIEdgeInsets {
    didSet {
        updateConstraintsForPlaceholderLabel()
    }
}

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

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

private func commonInit() {
    NSNotificationCenter.defaultCenter().addObserver(self,
                                                     selector: #selector(textDidChange),
                                                     name: UITextViewTextDidChangeNotification,
                                                     object: nil)

    placeholderLabel.font = font
    placeholderLabel.textColor = placeholderColor
    placeholderLabel.textAlignment = textAlignment
    placeholderLabel.text = placeholder
    placeholderLabel.numberOfLines = 0
    placeholderLabel.backgroundColor = UIColor.clearColor()
    placeholderLabel.translatesAutoresizingMaskIntoConstraints = false
    addSubview(placeholderLabel)
    updateConstraintsForPlaceholderLabel()
}

private func updateConstraintsForPlaceholderLabel() {
    var newConstraints = NSLayoutConstraint.constraintsWithVisualFormat("H:|-(\(textContainerInset.left + textContainer.lineFragmentPadding))-[placeholder]",
                                                                        options: [],
                                                                        metrics: nil,
                                                                        views: ["placeholder": placeholderLabel])
    newConstraints += NSLayoutConstraint.constraintsWithVisualFormat("V:|-(\(textContainerInset.top))-[placeholder]",
                                                                     options: [],
                                                                     metrics: nil,
                                                                     views: ["placeholder": placeholderLabel])
    newConstraints.append(NSLayoutConstraint(
        item: placeholderLabel,
        attribute: .Width,
        relatedBy: .Equal,
        toItem: self,
        attribute: .Width,
        multiplier: 1.0,
        constant: -(textContainerInset.left + textContainerInset.right + textContainer.lineFragmentPadding * 2.0)
        ))
    removeConstraints(placeholderLabelConstraints)
    addConstraints(newConstraints)
    placeholderLabelConstraints = newConstraints
}

@objc private func textDidChange() {
    placeholderLabel.hidden = !text.isEmpty
}

public override func layoutSubviews() {
    super.layoutSubviews()
    placeholderLabel.preferredMaxLayoutWidth = textContainer.size.width - textContainer.lineFragmentPadding * 2.0
}

deinit {
    NSNotificationCenter.defaultCenter().removeObserver(self,
                                                        name: UITextViewTextDidChangeNotification,
                                                        object: nil)
}

}

在swift3:

import UIKit

类 CustomTextView： { UITextView

private struct Constants {
    static let defaultiOSPlaceholderColor = UIColor(red: 0.0, green: 0.0, blue: 0.0980392, alpha: 0.22)
}
private let placeholderLabel: UILabel = UILabel()

private var placeholderLabelConstraints = [NSLayoutConstraint]()

@IBInspectable public var placeholder: String = "" {
    didSet {
        placeholderLabel.text = placeholder
    }
}

@IBInspectable public var placeholderColor: UIColor = CustomTextView.Constants.defaultiOSPlaceholderColor {
    didSet {
        placeholderLabel.textColor = placeholderColor
    }
}

override public var font: UIFont! {
    didSet {
        placeholderLabel.font = font
    }
}

override public var textAlignment: NSTextAlignment {
    didSet {
        placeholderLabel.textAlignment = textAlignment
    }
}

override public var text: String! {
    didSet {
        textDidChange()
    }
}

override public var attributedText: NSAttributedString! {
    didSet {
        textDidChange()
    }
}

override public var textContainerInset: UIEdgeInsets {
    didSet {
        updateConstraintsForPlaceholderLabel()
    }
}

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

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

private func commonInit() {
    NotificationCenter.default.addObserver(self,
                                                     selector: #selector(textDidChange),
                                                     name: NSNotification.Name.UITextViewTextDidChange,
                                                     object: nil)

    placeholderLabel.font = font
    placeholderLabel.textColor = placeholderColor
    placeholderLabel.textAlignment = textAlignment
    placeholderLabel.text = placeholder
    placeholderLabel.numberOfLines = 0
    placeholderLabel.backgroundColor = UIColor.clear
    placeholderLabel.translatesAutoresizingMaskIntoConstraints = false
    addSubview(placeholderLabel)
    updateConstraintsForPlaceholderLabel()
}

private func updateConstraintsForPlaceholderLabel() {
    var newConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:|-(\(textContainerInset.left + textContainer.lineFragmentPadding))-[placeholder]",
        options: [],
        metrics: nil,
        views: ["placeholder": placeholderLabel])
    newConstraints += NSLayoutConstraint.constraints(withVisualFormat: "V:|-(\(textContainerInset.top))-[placeholder]",
        options: [],
        metrics: nil,
        views: ["placeholder": placeholderLabel])
    newConstraints.append(NSLayoutConstraint(
        item: placeholderLabel,
        attribute: .width,
        relatedBy: .equal,
        toItem: self,
        attribute: .width,
        multiplier: 1.0,
        constant: -(textContainerInset.left + textContainerInset.right + textContainer.lineFragmentPadding * 2.0)
    ))
    removeConstraints(placeholderLabelConstraints)
    addConstraints(newConstraints)
    placeholderLabelConstraints = newConstraints
}

@objc private func textDidChange() {
    placeholderLabel.isHidden = !text.isEmpty
}

public override func layoutSubviews() {
    super.layoutSubviews()
    placeholderLabel.preferredMaxLayoutWidth = textContainer.size.width - textContainer.lineFragmentPadding * 2.0
}

deinit {
    NotificationCenter.default.removeObserver(self,
                                                        name: NSNotification.Name.UITextViewTextDidChange,
                                                        object: nil)
}

}

我用swift写了一个类。您需要在需要的时候导入这个类。

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
    }
}