如果你正在寻找一个简单的方法来实现这一点，试试我的方法:

- (BOOL)textViewShouldBeginEditing:(UITextView *)textView
{
    if ([[textView text] isEqualToString:PLACE_HOLDER_TEXT]) {
          textView.text = @"";
          textView.textColor = [UIColor blackColor];
    }

    return YES;
}

-(BOOL)textViewShouldEndEditing:(UITextView *)textView
{
    if ([[textView text] length] == 0) {
        textView.text = PLACE_HOLDER_TEXT;
        textView.textColor = [UIColor lightGrayColor];
    }
    return YES;
}

是的，就是它PLACE_HOLDER_TEXT是一个NSString包含你的占位符

我对发布的任何解决方案都不太满意，因为它们有点重。向视图中添加视图并不理想(尤其是在drawRect:)。它们都有漏洞，这也是不可接受的。

这是我的解决方案:SAMTextView

SAMTextView.h

//
//  SAMTextView.h
//  SAMTextView
//
//  Created by Sam Soffes on 8/18/10.
//  Copyright 2010-2013 Sam Soffes. All rights reserved.
//

#import <UIKit/UIKit.h>

/**
 UITextView subclass that adds placeholder support like UITextField has.
 */
@interface SAMTextView : UITextView

/**
 The string that is displayed when there is no other text in the text view.

 The default value is `nil`.
 */
@property (nonatomic, strong) NSString *placeholder;

/**
 The color of the placeholder.

 The default is `[UIColor lightGrayColor]`.
 */
@property (nonatomic, strong) UIColor *placeholderTextColor;

/**
 Returns the drawing rectangle for the text views’s placeholder text.

 @param bounds The bounding rectangle of the receiver.
 @return The computed drawing rectangle for the placeholder text.
 */
- (CGRect)placeholderRectForBounds:(CGRect)bounds;

@end

SAMTextView.m

//
//  SAMTextView.m
//  SAMTextView
//
//  Created by Sam Soffes on 8/18/10.
//  Copyright 2010-2013 Sam Soffes. All rights reserved.
//

#import "SAMTextView.h"

@implementation SAMTextView

#pragma mark - Accessors

@synthesize placeholder = _placeholder;
@synthesize placeholderTextColor = _placeholderTextColor;

- (void)setText:(NSString *)string {
  [super setText:string];
  [self setNeedsDisplay];
}


- (void)insertText:(NSString *)string {
  [super insertText:string];
  [self setNeedsDisplay];
}


- (void)setAttributedText:(NSAttributedString *)attributedText {
  [super setAttributedText:attributedText];
  [self setNeedsDisplay];
}


- (void)setPlaceholder:(NSString *)string {
  if ([string isEqual:_placeholder]) {
    return;
  }

  _placeholder = string;
  [self setNeedsDisplay];
}


- (void)setContentInset:(UIEdgeInsets)contentInset {
  [super setContentInset:contentInset];
  [self setNeedsDisplay];
}


- (void)setFont:(UIFont *)font {
  [super setFont:font];
  [self setNeedsDisplay];
}


- (void)setTextAlignment:(NSTextAlignment)textAlignment {
  [super setTextAlignment:textAlignment];
  [self setNeedsDisplay];
}


#pragma mark - NSObject

- (void)dealloc {
  [[NSNotificationCenter defaultCenter] removeObserver:self name:UITextViewTextDidChangeNotification object:self];
}


#pragma mark - UIView

- (id)initWithCoder:(NSCoder *)aDecoder {
  if ((self = [super initWithCoder:aDecoder])) {
    [self initialize];
  }
  return self;
}


- (id)initWithFrame:(CGRect)frame {
  if ((self = [super initWithFrame:frame])) {
    [self initialize];
  }
  return self;
}


- (void)drawRect:(CGRect)rect {
  [super drawRect:rect];

  if (self.text.length == 0 && self.placeholder) {
    rect = [self placeholderRectForBounds:self.bounds];

    UIFont *font = self.font ? self.font : self.typingAttributes[NSFontAttributeName];

    // Draw the text
    [self.placeholderTextColor set];
    [self.placeholder drawInRect:rect withFont:font lineBreakMode:NSLineBreakByTruncatingTail alignment:self.textAlignment];
  }
}


#pragma mark - Placeholder

- (CGRect)placeholderRectForBounds:(CGRect)bounds {
  // Inset the rect
  CGRect rect = UIEdgeInsetsInsetRect(bounds, self.contentInset);

  if (self.typingAttributes) {
    NSParagraphStyle *style = self.typingAttributes[NSParagraphStyleAttributeName];
    if (style) {
      rect.origin.x += style.headIndent;
      rect.origin.y += style.firstLineHeadIndent;
    }
  }

  return rect;
}


#pragma mark - Private

- (void)initialize {
  [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:self];

  self.placeholderTextColor = [UIColor colorWithWhite:0.702f alpha:1.0f];
}


- (void)textChanged:(NSNotification *)notification {
  [self setNeedsDisplay];
}

@end

它比其他的要简单得多，因为它不使用子视图(或有泄漏)。请随意使用。

更新11/10/11:它现在是文档化的，并支持在接口生成器中使用。

更新11/24/13:指向新的回购。

在UITextView中创建占位符是不可能的，但是你可以通过这个生成类似占位符的效果。

  - (void)viewDidLoad{      
              commentTxtView.text = @"Comment";
              commentTxtView.textColor = [UIColor lightGrayColor];
              commentTxtView.delegate = self;

     }
       - (BOOL) textViewShouldBeginEditing:(UITextView *)textView
     {
         commentTxtView.text = @"";
         commentTxtView.textColor = [UIColor blackColor];
         return YES;
     }

     -(void) textViewDidChange:(UITextView *)textView
     {

    if(commentTxtView.text.length == 0){
        commentTxtView.textColor = [UIColor lightGrayColor];
        commentTxtView.text = @"Comment";
        [commentTxtView resignFirstResponder];
    }
    }

或者你可以添加标签在textview就像

       lbl = [[UILabel alloc] initWithFrame:CGRectMake(10.0, 0.0,textView.frame.size.width - 10.0, 34.0)];


[lbl setText:kDescriptionPlaceholder];
[lbl setBackgroundColor:[UIColor clearColor]];
[lbl setTextColor:[UIColor lightGrayColor]];
textView.delegate = self;

[textView addSubview:lbl];

并设置

- (void)textViewDidEndEditing:(UITextView *)theTextView
{
     if (![textView hasText]) {
     lbl.hidden = NO;
}
}

- (void) textViewDidChange:(UITextView *)textView
{
    if(![textView hasText]) {
      lbl.hidden = NO;
}
else{
    lbl.hidden = YES;
 }  
}

我对bcd的解决方案做了一些小修改，以允许从Xib文件初始化、文本包装和保持背景颜色。希望它能为其他人省去麻烦。

UIPlaceHolderTextView.h:

#import <Foundation/Foundation.h>
IB_DESIGNABLE
@interface UIPlaceHolderTextView : UITextView

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

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

@end

UIPlaceHolderTextView.m:

#import "UIPlaceHolderTextView.h"

@interface UIPlaceHolderTextView ()

@property (nonatomic, retain) UILabel *placeHolderLabel;

@end

@implementation UIPlaceHolderTextView

CGFloat const UI_PLACEHOLDER_TEXT_CHANGED_ANIMATION_DURATION = 0.25;

- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
#if __has_feature(objc_arc)
#else
    [_placeHolderLabel release]; _placeHolderLabel = nil;
    [_placeholderColor release]; _placeholderColor = nil;
    [_placeholder release]; _placeholder = nil;
    [super dealloc];
#endif
}

- (void)awakeFromNib
{
    [super awakeFromNib];

    // Use Interface Builder User Defined Runtime Attributes to set
    // placeholder and placeholderColor in Interface Builder.
    if (!self.placeholder) {
        [self setPlaceholder:@""];
    }

    if (!self.placeholderColor) {
        [self setPlaceholderColor:[UIColor lightGrayColor]];
    }

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];
}

- (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 *)notification
{
    if([[self placeholder] length] == 0)
    {
        return;
    }

    [UIView animateWithDuration:UI_PLACEHOLDER_TEXT_CHANGED_ANIMATION_DURATION animations:^{
    if([[self text] length] == 0)
    {
        [[self viewWithTag:999] setAlpha:1];
    }
    else
    {
        [[self viewWithTag:999] setAlpha:0];
    }
    }];
}

- (void)setText:(NSString *)text {
    [super setText:text];
    [self textChanged:nil];
}

- (void)drawRect:(CGRect)rect
{
    if( [[self placeholder] length] > 0 )
    {
        if (_placeHolderLabel == nil )
        {
            _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];
}

@end

如果你正在寻找一个简单的方法来实现这一点，试试我的方法:

- (BOOL)textViewShouldBeginEditing:(UITextView *)textView
{
    if ([[textView text] isEqualToString:PLACE_HOLDER_TEXT]) {
          textView.text = @"";
          textView.textColor = [UIColor blackColor];
    }

    return YES;
}

-(BOOL)textViewShouldEndEditing:(UITextView *)textView
{
    if ([[textView text] length] == 0) {
        textView.text = PLACE_HOLDER_TEXT;
        textView.textColor = [UIColor lightGrayColor];
    }
    return YES;
}

是的，就是它PLACE_HOLDER_TEXT是一个NSString包含你的占位符

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