我通过使用两个不同的文本视图来做到这一点:

一个在后台用作占位符。 一个在前台(具有透明背景)，用户实际输入。

其思想是，一旦用户开始在前景视图中输入内容，后台的占位符就会消失(如果用户删除了所有内容，则会重新出现)。因此，它的行为完全类似于单行文本字段的占位符。

这是我用的代码。注意，descriptionField是用户键入的字段，descriptionPlaceholder是后台的字段。

func textViewDidChange(descriptionField: UITextView) {
    if descriptionField.text.isEmpty == false {
        descriptionPlaceholder.text = ""
    } else {
        descriptionPlaceholder.text = descriptionPlaceholderText
    }
}

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
    }
}

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()
}

这是我用来完成这项工作的方法。

@IBDesignable class UIPlaceholderTextView: UITextView {
    
    var placeholderLabel: UILabel?
    
    override init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame, textContainer: textContainer)
        sharedInit()
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        sharedInit()
    }
    
    override func prepareForInterfaceBuilder() {
        sharedInit()
    }
    
    func sharedInit() {
        refreshPlaceholder()
        NotificationCenter.default.addObserver(self, selector: #selector(textChanged), name: UITextView.textDidChangeNotification, object: nil)
    }

    @IBInspectable var placeholder: String? {
        didSet {
            refreshPlaceholder()
        }
    }

    @IBInspectable var placeholderColor: UIColor? = .darkGray {
        didSet {
            refreshPlaceholder()
        }
    }
    
    @IBInspectable var placeholderFontSize: CGFloat = 14 {
        didSet {
            refreshPlaceholder()
        }
    }
    
    func refreshPlaceholder() {
        if placeholderLabel == nil {
            placeholderLabel = UILabel()
            let contentView = self.subviews.first ?? self
            
            contentView.addSubview(placeholderLabel!)
            placeholderLabel?.translatesAutoresizingMaskIntoConstraints = false
            
            placeholderLabel?.leftAnchor.constraint(equalTo: contentView.leftAnchor, constant: textContainerInset.left + 4).isActive = true
            placeholderLabel?.rightAnchor.constraint(equalTo: contentView.rightAnchor, constant: textContainerInset.right + 4).isActive = true
            placeholderLabel?.topAnchor.constraint(equalTo: contentView.topAnchor, constant: textContainerInset.top).isActive = true
            placeholderLabel?.bottomAnchor.constraint(lessThanOrEqualTo: contentView.bottomAnchor, constant: textContainerInset.bottom).isActive = true
        }
        placeholderLabel?.text = placeholder
        placeholderLabel?.textColor = placeholderColor
        placeholderLabel?.font = UIFont.systemFont(ofSize: placeholderFontSize)
    }
    
    @objc func textChanged() {
        if self.placeholder?.isEmpty ?? true {
            return
        }
        
        UIView.animate(withDuration: 0.25) {
            if self.text.isEmpty {
                self.placeholderLabel?.alpha = 1.0
            } else {
                self.placeholderLabel?.alpha = 0.0
            }
        }
    }
    
    override var text: String! {
        didSet {
            textChanged()
        }
    }

}

我知道有很多类似的方法，但这个方法的好处是:

在IB中设置占位符文本、字体大小和颜色。 在IB中不再显示“滚动视图有不明确的可滚动内容”的警告。 添加动画显示/隐藏占位符。

我知道这是一个老问题，但想分享我认为是一个有用的方式扩展UITextView有placeholderText和placeholderColor字段。基本上你将UITextView转换为UITextField，然后设置attributedPlaceholder字段。PlaceholderText和placeholderColor是IBInspectable字段，所以它们的值可以在IB中设置，并与UITextField占位符功能完全相同。

UITextView+Extend.h

#import <UIKit/UIKit.h>

@interface UITextView (Extend)

@property (nonatomic) IBInspectable NSString *placeholderText;
@property (nonatomic) IBInspectable UIColor *placeholderColor;

@end

UITextView+Extend.m

#import "UITextView+Extend.h"
#import "objc/runtime.h"

@implementation UITextView (Extend)

- (void)setPlaceholderText:(NSString *)placeholderText
{
    objc_setAssociatedObject(self, @selector(placeholderText), placeholderText, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    [self updatePlaceholderText];
}

- (NSString*)placeholderText
{
    return objc_getAssociatedObject(self, @selector(placeholderText));
}

- (void)setPlaceholderColor:(UIColor *)placeholderColor
{
    objc_setAssociatedObject(self, @selector(placeholderColor), placeholderColor, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    [self updatePlaceholderText];
}

- (UIColor*)placeholderColor
{
    return objc_getAssociatedObject(self, @selector(placeholderColor));
}

- (void)updatePlaceholderText
{
    NSString *text = self.placeholderText;
    UIColor *color = self.placeholderColor;
    if(text && color)
    {
        UITextField *textField = (UITextField*)self;
        textField.attributedPlaceholder = [[NSAttributedString alloc] initWithString:text attributes:@{NSForegroundColorAttributeName:color}];
    }
}

@end

无需添加任何第三方库。只需使用下面的代码…

class SubmitReviewVC : UIViewController, UITextViewDelegate {

@IBOutlet var txtMessage : UITextView!
var lblPlaceHolder : UILabel!

override func viewDidLoad() {
    super.viewDidLoad()

    txtMessage.delegate = self
    lblPlaceHolder = UILabel()
    lblPlaceHolder.text = "Enter message..."
    lblPlaceHolder.font = UIFont.systemFont(ofSize: txtMessage.font!.pointSize)
    lblPlaceHolder.sizeToFit()
    txtMessage.addSubview(lblPlaceHolder)
    lblPlaceHolder.frame.origin = CGPoint(x: 5, y: (txtMessage.font?.pointSize)! / 2)
    lblPlaceHolder.textColor = UIColor.lightGray
    lblPlaceHolder.isHidden = !txtMessage.text.isEmpty
}

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

}