还有一个解决方案(Swift 3):

import UIKit

protocol PlaceholderTextViewDelegate {
    func placeholderTextViewDidChangeText(_ text:String)
    func placeholderTextViewDidEndEditing(_ text:String)
}

final class PlaceholderTextView: UITextView {

    var notifier:PlaceholderTextViewDelegate?

    var placeholder: String? {
        didSet {
            placeholderLabel?.text = placeholder
        }
    }
    var placeholderColor = UIColor.lightGray
    var placeholderFont = UIFont.appMainFontForSize(14.0) {
        didSet {
            placeholderLabel?.font = placeholderFont
        }
    }

    fileprivate var placeholderLabel: UILabel?

    // MARK: - LifeCycle

    init() {
        super.init(frame: CGRect.zero, textContainer: nil)
        awakeFromNib()
    }

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

    override func awakeFromNib() {
        super.awakeFromNib()

        self.delegate = self
        NotificationCenter.default.addObserver(self, selector: #selector(PlaceholderTextView.textDidChangeHandler(notification:)), name: .UITextViewTextDidChange, object: nil)

        placeholderLabel = UILabel()
        placeholderLabel?.textColor = placeholderColor
        placeholderLabel?.text = placeholder
        placeholderLabel?.textAlignment = .left
        placeholderLabel?.numberOfLines = 0
    }

    override func layoutSubviews() {
        super.layoutSubviews()

        placeholderLabel?.font = placeholderFont

        var height:CGFloat = placeholderFont.lineHeight
        if let data = placeholderLabel?.text {

            let expectedDefaultWidth:CGFloat = bounds.size.width
            let fontSize:CGFloat = placeholderFont.pointSize

            let textView = UITextView()
            textView.text = data
            textView.font = UIFont.appMainFontForSize(fontSize)
            let sizeForTextView = textView.sizeThatFits(CGSize(width: expectedDefaultWidth,
                                                               height: CGFloat.greatestFiniteMagnitude))
            let expectedTextViewHeight = sizeForTextView.height

            if expectedTextViewHeight > height {
                height = expectedTextViewHeight
            }
        }

        placeholderLabel?.frame = CGRect(x: 5, y: 0, width: bounds.size.width - 16, height: height)

        if text.isEmpty {
            addSubview(placeholderLabel!)
            bringSubview(toFront: placeholderLabel!)
        } else {
            placeholderLabel?.removeFromSuperview()
        }
    }

    func textDidChangeHandler(notification: Notification) {
        layoutSubviews()
    }

}

extension PlaceholderTextView : UITextViewDelegate {
    // MARK: - UITextViewDelegate
    func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
        if(text == "\n") {
            textView.resignFirstResponder()
            return false
        }
        return true
    }

    func textViewDidChange(_ textView: UITextView) {
        notifier?.placeholderTextViewDidChangeText(textView.text)
    }

    func textViewDidEndEditing(_ textView: UITextView) {
        notifier?.placeholderTextViewDidEndEditing(textView.text)
    }
}

结果

我们可以很容易地实现textview占位符，如果我们正在使用pod IQKeyboardManagerSwift在我们的项目中，只需遵循4个步骤

我们必须将类IQTextView分配给我们的TextView类。 我们必须在Controller页面中导入IQKeyboardManagerSwift 最后但并非最不重要的是，在控制器页面的textView的出口//如果你想:) 通过storyboard inspectable给textView一些占位符文本

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()
    }
}

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]

以下是我解决这个问题的方法(Swift 4):

这个想法是做出最简单的解决方案，允许使用不同颜色的占位符，调整占位符大小，不会覆盖委托，同时保持所有UITextView函数正常工作。

import UIKit

class PlaceholderTextView: UITextView {
    var placeholderColor: UIColor = .lightGray
    var defaultTextColor: UIColor = .black

    private var isShowingPlaceholder = false {
        didSet {
            if isShowingPlaceholder {
                text = placeholder
                textColor = placeholderColor
            } else {
                textColor = defaultTextColor
            }
        }
    }

    var placeholder: String? {
        didSet {
            isShowingPlaceholder = !hasText
        }
    }

    @objc private func textViewDidBeginEditing(notification: Notification) {
        textColor = defaultTextColor
        if isShowingPlaceholder { text = nil }
    }

    @objc private func textViewDidEndEditing(notification: Notification) {
        isShowingPlaceholder = !hasText
    }

    // MARK: - Construction -
    override init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame, textContainer: textContainer)
        setup()
    }

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

    private func setup() {
        NotificationCenter.default.addObserver(self, selector: #selector(textViewDidBeginEditing(notification:)), name: UITextView.textDidBeginEditingNotification, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(textViewDidEndEditing(notification:)), name: UITextView.textDidEndEditingNotification, object: nil)
    }

    // MARK: - Destruction -
    deinit { NotificationCenter.default.removeObserver(self) }
}

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
        }
    }
}