简单的Swift 3解决方案

添加UITextViewDelegate到类中

设置你的textview .delegate = self

创建placeholderLabel和位置它在你的textview

现在动画placeholderLabel。alpha在textViewDidChange:

  func textViewDidChange(_ textView: UITextView) {
    let newAlpha: CGFloat = textView.text.isEmpty ? 1 : 0
    if placeholderLabel.alpha != newAlpha {
      UIView.animate(withDuration: 0.3) {
        self.placeholderLabel.alpha = newAlpha
      }
    }
  }

你可能不得不使用placeholderLabel位置来设置它，但这应该不会太难

TextView占位符

import UIKit

@IBDesignable
open class KMPlaceholderTextView: UITextView {

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

    public let placeholderLabel: UILabel = UILabel()

    private var placeholderLabelConstraints = [NSLayoutConstraint]()

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

    @IBInspectable open var placeholderColor: UIColor = KMPlaceholderTextView.Constants.defaultiOSPlaceholderColor {
        didSet {
            placeholderLabel.textColor = placeholderColor
        }
    }

    override open var font: UIFont! {
        didSet {
            if placeholderFont == nil {
                placeholderLabel.font = font
            }
        }
    }

    open var placeholderFont: UIFont? {
        didSet {
            let font = (placeholderFont != nil) ? placeholderFont : self.font
            placeholderLabel.font = font
        }
    }

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

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

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

    override open 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() {
        #if swift(>=4.2)
        let notificationName = UITextView.textDidChangeNotification
        #else
        let notificationName = NSNotification.Name.UITextView.textDidChangeNotification
        #endif

        NotificationCenter.default.addObserver(self,
                                               selector: #selector(textDidChange),
                                               name: notificationName,
                                               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
        self.layoutIfNeeded()
    }

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

    deinit {
        #if swift(>=4.2)
        let notificationName = UITextView.textDidChangeNotification
        #else
        let notificationName = NSNotification.Name.UITextView.textDidChangeNotification
        #endif

        NotificationCenter.default.removeObserver(self,
                                                  name: notificationName,
                                                  object: nil)
    }

}

使用

Jason的答案在iOS7中看起来有点不对劲，通过调整_placeHolderLabel的偏移量来修复它:

- (void)drawRect:(CGRect)rect
{
    if( [[self placeholder] length] > 0 )
    {
        if (_placeHolderLabel == nil )
        {
            if ([[UIDevice currentDevice].systemVersion floatValue] >= 7)
                _placeHolderLabel = [[UILabel alloc] initWithFrame:CGRectMake(4,8,self.bounds.size.width - 8,0)];
            else
                _placeHolderLabel = [[UILabel alloc] initWithFrame:CGRectMake(8,8,self.bounds.size.width - 16,0)];
            _placeHolderLabel.lineBreakMode = NSLineBreakByWordWrapping;
            _placeHolderLabel.numberOfLines = 0;
            _placeHolderLabel.font = self.font;
            _placeHolderLabel.backgroundColor = [UIColor clearColor];
            _placeHolderLabel.textColor = self.placeholderColor;
            _placeHolderLabel.alpha = 0;
            _placeHolderLabel.tag = 999;
            [self addSubview:_placeHolderLabel];
        }

        _placeHolderLabel.text = self.placeholder;
        [_placeHolderLabel sizeToFit];
        [self sendSubviewToBack:_placeHolderLabel];
    }

    if( [[self text] length] == 0 && [[self placeholder] length] > 0 )
    {
        [[self viewWithTag:999] setAlpha:1];
    }

    [super drawRect:rect];
}

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)
}
}

一个更简单的方法是创建一个次要的UITextView，它具有与原始文本视图相同的所有属性，除了不同的textColor，并带有约束以确保它们保持对齐。然后当任何字符进入主文本视图时，隐藏克隆文本视图，否则显示带有一些文本的克隆文本视图。

这可以通过几种方式实现，但相对简单的方法是子类化UITextView并将所有这些逻辑保留在子类中。

所以，子类UITextView并允许它惰性地创建它的占位符视图

接口文件:

@interface FOOTextView : UITextView <UITextViewDelegate>

@property (nonatomic, copy) NSString *placeholderText;

- (void)checkPlaceholder;

@end

实现文件:

#import "FOOTextView.h"

@interface FOOTextView ()

@property (nonatomic, strong) UITextView *placeholderTextView;

@end

@implementation FOOTextView

- (void)checkPlaceholder {
    // Hide the placeholder text view if we've got any text
    self.placeholderTextView.hidden = (self.text.length > 0 || self.attributedText.length > 0);
}

- (void)setPlaceholderText:(NSString *)placeholderText {
    _placeholderText = [placeholderText copy];

    // Setup the placeholder text view if we haven't already
    [self setupPlaceholderTextView];

    // Apply the placeholder text to the placeholder text view
    self.placeholderTextView.text = placeholderText;
}

- (void)setupPlaceholderTextView {
    if (!self.placeholderTextView) {

        // Setup the place holder text view, duplicating our visual setup
        self.placeholderTextView = [[UITextView alloc] initWithFrame:CGRectZero];
        self.placeholderTextView.translatesAutoresizingMaskIntoConstraints = NO;
        self.placeholderTextView.textColor = self.placeholderTextColor ? self.placeholderTextColor : [UIColor colorWithRed:199.f/255.f green:199.f/255.f blue:205.f/255.f alpha:1.f];
        self.placeholderTextView.userInteractionEnabled = NO;
        self.placeholderTextView.font = self.font;
        self.placeholderTextView.textAlignment = self.textAlignment;
        self.placeholderTextView.backgroundColor = self.backgroundColor;
        self.placeholderTextView.editable = NO;

        // Our background color must be clear for the placeholder text view to show through
        self.backgroundColor = [UIColor clearColor];

        // Insert the placeholder text view into our superview, below ourself so it shows through
        [self.superview insertSubview:self.placeholderTextView belowSubview:self];

        // Setup constraints to ensure the placeholder text view stays aligned with us
        NSLayoutConstraint *constraintCenterX = [NSLayoutConstraint constraintWithItem:self.placeholderTextView attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeCenterX multiplier:1.f constant:0.f];
        NSLayoutConstraint *constraintCenterY = [NSLayoutConstraint constraintWithItem:self.placeholderTextView attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeCenterY multiplier:1.f constant:0.f];
        NSLayoutConstraint *constraintWidth = [NSLayoutConstraint constraintWithItem:self.placeholderTextView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeWidth multiplier:1.f constant:0.f];
        NSLayoutConstraint *constraintHeight = [NSLayoutConstraint constraintWithItem:self.placeholderTextView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeHeight multiplier:1.f constant:0.f];
        NSArray *constraints = @[constraintCenterX, constraintCenterY, constraintWidth, constraintHeight];
        [self.superview addConstraints:constraints];

    }
}

- (void)setPlaceholderTextColor:(UIColor *)placeholderTextColor {
    _placeholderTextColor = placeholderTextColor;
    self.placeholderTextView.textColor = _placeholderTextColor;
}

- (void)setBackgroundColor:(UIColor *)backgroundColor {
    // We don't want a background color ourselves, instead we want our placeholder text view to have the desired background color
    [self.placeholderTextView setBackgroundColor:backgroundColor];
}

- (void)removeFromSuperview {
    // Ensure we also remove our placeholder text view
    [self.placeholderTextView removeFromSuperview];
    self.placeholderTextView = nil;
    [super removeFromSuperview];
}

#pragma mark - Text View Delegation 
- (void)textViewDidChange:(UITextView *)textView {
    [self checkPlaceholder];
}

@end

使用上面的类，如果你设置了一个FOOTextView的委托实例到它自己，一切都将开箱工作:

FOOTextView *myTextView = ...
myTextView.placeholderText = @"What's on your mind?";
myTextView.placeholderTextColor = [UIColor lightGrayColor];
myTextView.delegate = myTextView;

如果你想另一个对象接管作为委托，那么你只需要在textViewDidChange: delegate方法中调用文本视图的checkPlaceholder方法，例如;

FOOTextView *myTextView = ...
myTextView.placeholderText = @"What's on your mind?";
myTextView.placeholderTextColor = [UIColor lightGrayColor];
myTextView.delegate = self;
self.myTextView = myTextView;

- (void)textViewDidChange:(UITextView *)textView {
    // Call the checkPlaceholder method to update the visuals
    [self.myTextView checkPlaceholder];
}

在UITextView PlaceholderTextView中支持图标属性占位符的简单类

@IBOutlet weak var tvMessage: PlaceholderTextView!
//  TODO: - Create Icon Text Attachment
let icon: NSTextAttachment = NSTextAttachment()
icon.image = UIImage(named: "paper-plane")
let iconString = NSMutableAttributedString(attributedString: NSAttributedString(attachment: icon))

tvMessage.icon = icon

//  TODO: - Attributes
let textColor = UIColor.gray
let lightFont = UIFont(name: "Helvetica-Light", size: tvMessage.font!.pointSize)
let italicFont = UIFont(name: "Helvetica-LightOblique", size: tvMessage.font!.pointSize)

//  TODO: - Placeholder Attributed String
let message = NSAttributedString(string: " " + "Personal Message", attributes: [ NSFontAttributeName: lightFont!,   NSForegroundColorAttributeName: textColor])
iconString.append(message)
// TODO: - Italic Placeholder Part
let option = NSAttributedString(string: " " + "Optional", attributes: [ NSFontAttributeName: italicFont!, NSForegroundColorAttributeName: textColor])
iconString.append(option)

tvMessage.attributedPlaceHolder = iconString

tvMessage.layoutSubviews()