- (BOOL) textViewShouldBeginEditing:(UITextView *)textView
{
    //NSLog(@"textViewShouldBeginEditing");
    if( [tvComment.text isEqualToString:@"Comment"] && [tvComment.textColor isEqual:[UIColor lightGrayColor]] ){
        tvComment.text = @"";
        tvComment.textColor = [UIColor blackColor];
    }
    return YES;
}

- (void)keyboardWillBeHidden:(NSNotification*)aNotification{
    //NSLog(@"keyboardWillBeHidden");

    //Manage comment field placeholdertext
    if(tvComment.text.length == 0){
        tvComment.textColor = [UIColor lightGrayColor];
        tvComment.text = @"Comment";
    }
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    tvComment.textColor = [UIColor lightGrayColor];
}

TVComment是包含问题中的textView的属性。这样就可以了。

这里有一个更简单的解决方案，它的行为完全像UITextField的占位符，但不需要绘制自定义视图，或辞职第一响应器。

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

    if (textView.text.length == 0){
        textView.textColor = [UIColor lightGrayColor];
        textView.text = placeholderText;
        [textView setSelectedRange:NSMakeRange(0, 0)];
        isPlaceholder = YES;

    } else if (isPlaceholder && ![textView.text isEqualToString:placeholderText]) {
        textView.text = [textView.text substringToIndex:1];
        textView.textColor = [UIColor blackColor];
        isPlaceholder = NO;
    }

}

(else if语句中的第二个检查是针对没有输入任何内容且用户按下退格键的情况)

只需要将你的类设置为UITextViewDelegate。在viewDidLoad中，你应该这样初始化

- (void) viewDidLoad{
    // initialize placeholder text
    placeholderText = @"some placeholder";
    isPlaceholder = YES;
    self.someTextView.text = placeholderText;
    self.someTextView.textColor = [UIColor lightGrayColor];
    [self.someTextView setSelectedRange:NSMakeRange(0, 0)];

    // assign UITextViewDelegate
    self.someTextView.delegate = self;
}

另一个答案是:

https://github.com/gcamp/GCPlaceholderTextView

改变类UITextView在IB到GCPlaceholderTextView 并设置占位符属性

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。

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];
    }
}

After looking through (and trying out) most of the proposed solutions to this seemingly obvious - but missing - feature of UITextView, the 'best' closest I found was that from BobDickinson. But I didnt like having to resort to a whole new subclass [I prefer drop-in categories for such simple functional additions], nor that it intercepted UITextViewDelegate methods, which is probably going to mess up your existing UITextView handling code. So here's my take on a drop-in category that'll work on any existing UITextView instance...

#import <objc/runtime.h>

// Private subclass needed to override placeholderRectForBounds: to correctly position placeholder
@interface _TextField : UITextField
@property UIEdgeInsets insets;
@end
@implementation _TextField
- (CGRect)placeholderRectForBounds:(CGRect)bounds
{
    CGRect rect = [super placeholderRectForBounds:bounds];
    return UIEdgeInsetsInsetRect(rect, _insets);
}
@end

@implementation UITextView (Placeholder)

static const void *KEY;

- (void)setPlaceholder:(NSString *)placeholder
{
    _TextField *textField = objc_getAssociatedObject(self, &KEY);
    if (!textField) {
        textField = [_TextField.alloc initWithFrame:self.bounds];
        textField.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
        textField.userInteractionEnabled = NO;
        textField.font = self.font;

        textField.contentVerticalAlignment = UIControlContentVerticalAlignmentTop;
        textField.insets = UIEdgeInsetsMake(self.textContainerInset.top,
                                            self.textContainerInset.left + self.textContainer.lineFragmentPadding,
                                            self.textContainerInset.bottom,
                                            self.textContainerInset.right);
        [self addSubview:textField];
        [self sendSubviewToBack:textField];

        objc_setAssociatedObject(self, &KEY, textField, OBJC_ASSOCIATION_RETAIN);

        [NSNotificationCenter.defaultCenter addObserver:self selector:@selector(updatePlaceholder:) name:UITextViewTextDidChangeNotification object:nil];
    }
    textField.placeholder = placeholder;
}

- (NSString*)placeholder
{
    UITextField *textField = objc_getAssociatedObject(self, &KEY);
    return textField.placeholder;
}

- (void)updatePlaceholder:(NSNotification *)notification
{
    UITextField *textField = objc_getAssociatedObject(self, &KEY);
    textField.font = self.font;
    [textField setAlpha:self.text.length? 0 : 1];
}

@end

它使用简单，只是显而易见的

UITextView *myTextView = UITextView.new;
...
myTextView.placeholder = @"enter text here";

它通过添加一个UITextField -在正确的位置-在你的UITextView后面，并利用它的占位符代替(因此你不必担心得到正确的颜色等)，然后监听通知，每当你的UITextView被改变显示/隐藏这个UITextField(因此它不会干扰你现有的UITextViewDelegate调用)。这里面没有什么神奇的数字……: -)

objc_setAssociatedObject()/objc_getAssociatedObject()是为了避免必须子类化UITextView。[不幸的是，要正确地定位UITextField，有必要引入一个'private'子类，以覆盖placeholderRectForBounds:]

改编自BobDickinson的斯威夫特回答。