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;
 }  
}

在尝试了一些建议的方法后，我写了一个更清晰的实现，并将其发布到Github上。拉请求和问题是欢迎的。

与其他方法相比，这里提出了一些关键的改进:

不会在drawRect:中分配一个UILabel。(请不要这样做。) 不将文本视图的当前文本与所需的占位符进行比较以交换颜色。 当听写处于活动状态时隐藏占位符(如UITextField)。

我扩展了KmKndy的答案，这样在用户开始编辑UITextView之前，占位符仍然是可见的，而不仅仅是点击它。这反映了Twitter和Facebook应用程序的功能。我的解决方案不需要你子类和工作，如果用户类型直接或粘贴文本!

- (void)textViewDidChangeSelection:(UITextView *)textView{
    if ([textView.text isEqualToString:@"What's happening?"] && [textView.textColor isEqual:[UIColor lightGrayColor]])[textView setSelectedRange:NSMakeRange(0, 0)];

}

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

    [textView setSelectedRange:NSMakeRange(0, 0)];
}

- (void)textViewDidChange:(UITextView *)textView
{
    if (textView.text.length != 0 && [[textView.text substringFromIndex:1] isEqualToString:@"What's happening?"] && [textView.textColor isEqual:[UIColor lightGrayColor]]){
        textView.text = [textView.text substringToIndex:1];
        textView.textColor = [UIColor blackColor]; //optional

    }
    else if(textView.text.length == 0){
        textView.text = @"What's happening?";
        textView.textColor = [UIColor lightGrayColor];
        [textView setSelectedRange:NSMakeRange(0, 0)];
    }
}

- (void)textViewDidEndEditing:(UITextView *)textView
{
    if ([textView.text isEqualToString:@""]) {
        textView.text = @"What's happening?";
        textView.textColor = [UIColor lightGrayColor]; //optional
    }
    [textView resignFirstResponder];
}

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text{
    if (textView.text.length > 1 && [textView.text isEqualToString:@"What's happening?"]) {
         textView.text = @"";
         textView.textColor = [UIColor blackColor];
    }

    return YES;
}

只需要记住在创建时使用准确的文本设置myUITextView即可。

UITextView *myUITextView = [[UITextView alloc] init];
myUITextView.delegate = self;
myUITextView.text = @"What's happening?";
myUITextView.textColor = [UIColor lightGrayColor]; //optional

在包含这些方法之前，让父类成为一个UITextView委托。

@interface MyClass () <UITextViewDelegate>
@end

首先在.h文件中取一个标签。

这里我取

UILabel * lbl;

然后在。m中viewDidLoad下声明它

lbl = [[UILabel alloc] initWithFrame:CGRectMake(8.0, 0.0,250, 34.0)];

lbl.font=[UIFont systemFontOfSize:14.0];

[lbl setText:@"Write a message..."];

[lbl setBackgroundColor:[UIColor clearColor]];

[lbl setTextColor:[UIColor lightGrayColor]];

[textview addSubview:lbl];

textview是我的textview。

现在声明

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

 if (![textView hasText]){

    lbl.hidden = NO;

 }
 else{
    lbl.hidden = YES;
 }

}

和你的Textview占位符准备好了!

我创建了一个实例变量来检查是否显示占位符:

BOOL showPlaceHolder;
UITextView * textView; // and also the textView

在viewDidLoad上设置:

[self setPlaceHolder]; 

下面是它的作用:

- (void)setPlaceholder
{
    textView.text = NSLocalizedString(@"Type your question here", @"placeholder");
    textView.textColor = [UIColor lightGrayColor];
    self.showPlaceHolder = YES; //we save the state so it won't disappear in case you want to re-edit it
}

我还创建了一个按钮来退出键盘。您不必这样做，但这里很酷的事情是，如果没有输入任何内容，占位符将再次显示

- (void)textViewDidBeginEditing:(UITextView *)txtView 
{
    self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"Done" style:UIBarButtonItemStyleDone target:self action:@selector(resignKeyboard)];
    if (self.showPlaceHolder == YES) 
    {
        textView.textColor = [UIColor blackColor];
        textView.text = @"";
        self.showPlaceHolder = NO;
    }
}

- (void)resignKeyboard 
{
    [textView resignFirstResponder];
    //here if you created a button like I did to resign the keyboard, you should hide it
    if (textView.text.length == 0) {
        [self setPlaceholder];
    }       
}

还有一个简单的答案，使用CATextLayer。

添加CATextLayer到UITextView的层。 使用UITextViewDelegate方法，简单地改变CATextLayer的颜色。

func txtViewPlaceholder() {
    let textlayer = CATextLayer()

    textlayer.frame = CGRect(x: 5, y: 5, width: 200, height: 18)
    textlayer.contentsScale = UIScreen.main.scale
    textlayer.fontSize = 12
    textlayer.alignmentMode = kCAAlignmentLeft
    textlayer.string = "Enter here"
    textlayer.isWrapped = true
    textlayer.name = "placeholder"
    textlayer.backgroundColor = UIColor.white.cgColor
    textlayer.foregroundColor = UIColor.black.cgColor

    yourTxtVw.layer.insertSublayer(textlayer, at: 0)
}

func removeAddPlaceholder(remove: Bool, textView: UITextView) {
    for layers in textView.layer.sublayers! where layers.name == "placeholder" {
        
        if remove {
            (layers as! CATextLayer).foregroundColor = UIColor.white.cgColor
        } else {
            (layers as! CATextLayer).foregroundColor = UIColor.black.cgColor
        }
        
    }
}


extension YourViewController : UITextViewDelegate {

    func textViewShouldBeginEditing(_ textView: UITextView) -> Bool {
    
        removeAddPlaceholder(remove: true, textView: textView)
    
        return true
    }

    func textViewDidEndEditing(_ textView: UITextView) {
    
        if textView.text.count <= 0 {
            removeAddPlaceholder(remove: false, textView: textView)
        }
    }

}