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)
        }
    }

}

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;
}

在h课上

@interface RateCommentViewController : UIViewController<UITextViewDelegate>{IBoutlet UITextview *commentTxtView;}

在。m类

- (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];
    }
}

你可以在textview上设置一个标签。

MyUITextView.h

@interface MyUITextView : UITextView {
    UILabel* _placeholderLabel;
}

@property(nonatomic, assign)NSString *placeholder;

MyUITextView.m

@implementation MyUITextView

- (id)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        // Create placeholder
        viewFrame = CGRectMake(0, 0, frame.size.width, 15);
        _placeholderLabel = [[UILabel alloc] initWithFrame:viewFrame];
        _placeholderLabel.textColor = [UIColor lightGrayColor];
        [self addSubview:_placeholderLabel];

        // Add text changed notification 
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];
    }
    return self;
}

- (void)setPlaceholder:(NSString *)placeholder {
    _placeholderLabel.text = placeholder;
}

- (NSString*)placeholder {
    return _placeholderLabel.text;
}

#pragma mark UITextViewTextDidChangeNotification

- (void)textChanged:(NSNotification *)notification {
    _placeholderLabel.hidden = ([self.text lenght] == 0);
}

@end

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)
        }
    }

}

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];
    }       
}