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!

更简单，并且仍然考虑到用户在某些时候输入的一些文本

BOOL placeHolderTextVisible;

在viewDidLoad上，设置它为YES(或DidMoveToSuperview，或awakeFromNib)

然后,在 - (BOOL) textView:(UITextView*)textView shouldBeginEditing

    - (BOOL)textViewShouldBeginEditing:(UITextView *)textView;
{
   if (placeHolderTextVisible) {
    placeHolderTextVisible = NO;
    textView.text = @"";
   }
 return YES;
}

我刚刚发现，在iOS 10中，你现在可以将UITextView转换为方法的UITextField，并在方法中设置占位符。刚试过，它不需要子类化UITextView就能工作。

下面是一个对我有用的例子:

-(void)customizeTextField:(UITextField *)textField placeholder:(NSString *)pText withColor:(UIColor *)pTextColor{

        textField.attributedPlaceholder = [[NSAttributedString alloc]
                                          initWithString:pText
                                          attributes:@{NSForegroundColorAttributeName:pTextColor}];
    }

为了将它用于UITextView，你只需要将它传递给方法，使用像这样的类型转换:

[self customizeTextField:(UITextField*)_myTextView placeholder:@"Placeholder" withColor:[UIColor blackColor]];

注:经过测试，我发现这个解决方案在iOS9上也很好。但是会在iOS8.x上导致崩溃

你能做的是在文本属性中设置文本视图的初始值，并将textColor更改为[UIColor grayColor]或类似的东西。然后，每当文本视图变为可编辑时，清除文本并显示游标，如果文本字段再次为空，则将占位符文本放回。根据需要将颜色更改为[UIColor blackColor]。

它与UITextField中的占位符功能不完全相同，但很接近。

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()

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