在视图加载中设置值

    txtVw!.autocorrectionType = UITextAutocorrectionType.No
    txtVw!.text = "Write your Placeholder"
    txtVw!.textColor = UIColor.lightGrayColor()



func textViewDidBeginEditing(textView: UITextView) {
    if (txtVw?.text == "Write your Placeholder")

    {
        txtVw!.text = nil
        txtVw!.textColor = UIColor.blackColor()
    }
}

func textViewDidEndEditing(textView: UITextView) {
    if txtVw!.text.isEmpty
    {
        txtVw!.text = "Write your Placeholder"
        txtVw!.textColor = UIColor.lightGrayColor()
    }
    textView.resignFirstResponder()
}

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。

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

我不得不调度队列，让我的占位符文本重新出现，一旦编辑完成。

func textViewDidBeginEditing(_ textView: UITextView) {

    if textView.text == "Description" {
        textView.text = nil
    }
}

func textViewDidEndEditing(_ textView: UITextView) {

    if textView.text.isEmpty {
        DispatchQueue.main.async {
            textView.text = "Description"
        }
    }
}

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)
    }
    
}

协议版本的clearlight的答案上面，因为协议是伟大的。随便放哪都行。扣篮!

extension UITextViewPlaceholder where Self: UIViewController {

    // Use this in ViewController's ViewDidLoad method.
    func addPlaceholder(text: String, toTextView: UITextView, font: UIFont? = nil) {
        placeholderLabel = UILabel()
        placeholderLabel.text = text
        placeholderLabel.font = font ?? UIFont.italicSystemFont(ofSize: (toTextView.font?.pointSize)!)
        placeholderLabel.sizeToFit()
        toTextView.addSubview(placeholderLabel)
        placeholderLabel.frame.origin = CGPoint(x: 5, y: (toTextView.font?.pointSize)! / 2)
        placeholderLabel.textColor = UIColor.lightGray
        placeholderLabel.isHidden = !toTextView.text.isEmpty
    }

    // Use this function in the ViewController's textViewDidChange delegate method.
    func textViewWithPlaceholderDidChange(_ textView: UITextView) {
        placeholderLabel.isHidden = !textView.text.isEmpty
    }
}