下面是swift 3.1的代码

原始代码由杰森乔治在第一个答案。

不要忘记设置你的自定义类的TextView在接口生成器UIPlaceHolderTextView，然后设置占位符和占位符属性。

import UIKit

@IBDesignable
class UIPlaceHolderTextView: UITextView {

@IBInspectable var placeholder: String = ""
@IBInspectable var placeholderColor: UIColor = UIColor.lightGray

private let uiPlaceholderTextChangedAnimationDuration: Double = 0.05
private let defaultTagValue = 999

private var placeHolderLabel: UILabel?

override func awakeFromNib() {
    super.awakeFromNib()
    NotificationCenter.default.addObserver(
        self,
        selector: #selector(textChanged),
        name: NSNotification.Name.UITextViewTextDidChange,
        object: nil
    )
}

override init(frame: CGRect, textContainer: NSTextContainer?) {
    super.init(frame: frame, textContainer: textContainer)
    NotificationCenter.default.addObserver(
        self,
        selector: #selector(textChanged),
        name: NSNotification.Name.UITextViewTextDidChange,
        object: nil
    )
}

required init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
    NotificationCenter.default.addObserver(
        self,
        selector: #selector(textChanged),
        name: NSNotification.Name.UITextViewTextDidChange,
        object: nil
    )
}

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

@objc private func textChanged() {
    guard !placeholder.isEmpty else {
        return
    }
    UIView.animate(withDuration: uiPlaceholderTextChangedAnimationDuration) {
        if self.text.isEmpty {
            self.viewWithTag(self.defaultTagValue)?.alpha = CGFloat(1.0)
        }
        else {
            self.viewWithTag(self.defaultTagValue)?.alpha = CGFloat(0.0)
        }
    }
}

override var text: String! {
    didSet{
        super.text = text
        textChanged()
    }
}

override func draw(_ rect: CGRect) {
    if !placeholder.isEmpty {
        if placeHolderLabel == nil {
            placeHolderLabel = UILabel.init(frame: CGRect(x: 0, y: 8, width: bounds.size.width - 16, height: 0))
            placeHolderLabel!.lineBreakMode = .byWordWrapping
            placeHolderLabel!.numberOfLines = 0
            placeHolderLabel!.font = font
            placeHolderLabel!.backgroundColor = UIColor.clear
            placeHolderLabel!.textColor = placeholderColor
            placeHolderLabel!.alpha = 0
            placeHolderLabel!.tag = defaultTagValue
            self.addSubview(placeHolderLabel!)
        }

        placeHolderLabel!.text = placeholder
        placeHolderLabel!.sizeToFit()
        self.sendSubview(toBack: placeHolderLabel!)

        if text.isEmpty && !placeholder.isEmpty {
            viewWithTag(defaultTagValue)?.alpha = 1.0
        }
    }

    super.draw(rect)
}
}

这里还有另一种方法，它复制了UITextField占位符的轻微缩进:

将UITextField拖到UITextView的右边，这样它们的左上角就对齐了。将占位符文本添加到文本字段。

在viewDidLoad中添加:

[tView setDelegate:self];
tView.contentInset = UIEdgeInsetsMake(-8,-8,0,0);
tView.backgroundColor = [UIColor clearColor];

然后添加:

- (void)textViewDidChange:(UITextView *)textView {
    if (textView.text.length == 0) {
        textView.backgroundColor = [UIColor clearColor];            
    } else {
        textView.backgroundColor = [UIColor whiteColor];
    }
}

我是这样做的:

UITextView2.h

#import <UIKit/UIKit.h>

@interface UITextView2 : UITextView <UITextViewDelegate> {
 NSString *placeholder;
 UIColor *placeholderColor;
}

@property(nonatomic, retain) NSString *placeholder;
@property(nonatomic, retain) UIColor *placeholderColor;

-(void)textChanged:(NSNotification*)notif;

@end

UITextView2.m

@implementation UITextView2

@synthesize placeholder, placeholderColor;

- (id)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        [self setPlaceholder:@""];
        [self setPlaceholderColor:[UIColor lightGrayColor]];
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];
    }
    return self;
}

-(void)textChanged:(NSNotification*)notif {
    if ([[self placeholder] length]==0)
        return;
    if ([[self text] length]==0) {
        [[self viewWithTag:999] setAlpha:1];
    } else {
        [[self viewWithTag:999] setAlpha:0];
    }

}

- (void)drawRect:(CGRect)rect {
    if ([[self placeholder] length]>0) {
        UILabel *l = [[UILabel alloc] initWithFrame:CGRectMake(8, 8, 0, 0)];
        [l setFont:self.font];
        [l setTextColor:self.placeholderColor];
        [l setText:self.placeholder];
        [l setAlpha:0];
        [l setTag:999];
        [self addSubview:l];
        [l sizeToFit];
        [self sendSubviewToBack:l];
        [l release];
    }
    if ([[self text] length]==0 && [[self placeholder] length]>0) {
        [[self viewWithTag:999] setAlpha:1];
    }
    [super drawRect:rect];
}

- (void)dealloc {
    [[NSNotificationCenter defaultCenter] removeObserver:self];
    [super dealloc];
}


@end

这是我的版本的UITextView与占位符支持。斯威夫特4.2 https://gist.github.com/hlung/c5dda3a0c2087e5ae6c1fce8822c4713

一个支持占位符文本的UITextView子类。它使用另一个 UILabel显示占位符，当文本为空时显示。

在swift 5。工作很好。

class BaseTextView: UITextView {

    // MARK: - Views
    private var placeholderLabel: UIlabel!

    // MARK: - Init
    override init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame, textContainer: textContainer)
        setupUI()
        startupSetup()
    }

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

    deinit {
        NotificationCenter.default.removeObserver(self)
    }    
}

// MARK: - Setup UI
private extension BaseTextView {
    func setupUI() {
        addPlaceholderLabel()

        textColor = .textColor
    }

    func addPlaceholderLabel() {
        placeholderLabel = BaseLabel(frame: .zero)
        placeholderLabel.translatesAutoresizingMaskIntoConstraints = false
        insertSubview(placeholderLabel, at: 0)

        placeholderLabel.alpha = 0
        placeholderLabel.numberOfLines = 0
        placeholderLabel.backgroundColor = .clear
        placeholderLabel.textColor = .lightTextColor
        placeholderLabel.lineBreakMode = .byWordWrapping
        placeholderLabel.isUserInteractionEnabled = false
        placeholderLabel.font = UIFont.openSansSemibold.withSize(12)

        placeholderLabel.topAnchor.constraint(equalTo: topAnchor, constant: 8).isActive = true
        placeholderLabel.leftAnchor.constraint(equalTo: leftAnchor, constant: 5).isActive = true
        placeholderLabel.rightAnchor.constraint(lessThanOrEqualTo: rightAnchor, constant: -8).isActive = true
        placeholderLabel.bottomAnchor.constraint(lessThanOrEqualTo: bottomAnchor, constant: -8).isActive = true
    }
}

// MARK: - Startup
private extension BaseTextView {
    func startupSetup() {
        addObservers()
        textChanged(nil)
        font = UIFont.openSansSemibold.withSize(12)
    }    

    func addObservers() {
        NotificationCenter.default.addObserver(self, selector: #selector(textChanged(_:)), name: UITextView.textDidChangeNotification, object: nil)
    }
}

// MARK: - Actions
private extension BaseTextView {
    @objc func textChanged(_ sender: Notification?) {
        UIView.animate(withDuration: 0.2) {
            self.placeholderLabel.alpha = self.text.count == 0 ? 1 : 0
        }    
    }
}

// MARK: - Public methods
extension BaseTextView {
    public func setPlaceholder(_ placeholder: String) {
        placeholderLabel.text = placeholder
    }
}

在代码行中使用它的简单方法:

取一个标签到。nib中的UITextView 将这个标签连接到你的代码， 在它。

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text{

    if (range.location>0 || text.length!=0) {
        placeholderLabel1.hidden = YES;
    }else{
        placeholderLabel1.hidden = NO;
    }
    return YES;
}