- (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。

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)
        }
    }

}

I know there are already a lot of answers to this one, but I didn't really find any of them sufficient (at least in Swift). I needed the "placeholder" functionality of the UITextField in my UITextView (I wanted the exact behavior, including text display attributes, animations, etc, and didn't want to have to maintain this over time). I also wanted a solution that provided the same exact border as a UITextField (not an approximated one that looks sort of like it looks right now, but one that looks exactly like it and will always look exactly like it). So while I was not initially a fan of jamming an extra control into the mix, it seemed that in order to meet my goals I had to use an actual UITextField and let it do the work.

这个解决方案处理定位占位符和保持字体在两个控件之间的同步，以便占位符文本是输入到控件的文本的确切字体和位置(许多其他解决方案没有解决的问题)。

// This class is necessary to support "inset" (required to position placeholder 
// appropriately in TextView)
//
class TextField: UITextField
{
    var inset: UIEdgeInsets = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0);

    override func textRectForBounds(bounds: CGRect) -> CGRect
    {
        return UIEdgeInsetsInsetRect(bounds, inset);
    }

    override func placeholderRectForBounds(bounds: CGRect) -> CGRect
    {
        return UIEdgeInsetsInsetRect(bounds, inset);
    }
}

// This class implements a UITextView that has a UITextField behind it, where the 
// UITextField provides the border and the placeholder text functionality (so that the
// TextView looks and works like a UITextField).
//
class TextView : UITextView, UITextViewDelegate
{
    var textField = TextField();

    required init?(coder: NSCoder)
    {
        super.init(coder: coder);
    }

    override init(frame: CGRect, textContainer: NSTextContainer?)
    {
        super.init(frame: frame, textContainer: textContainer);

        self.delegate = self;

        // Create a background TextField with clear (invisible) text and disabled
        self.textField.borderStyle = UITextBorderStyle.RoundedRect;
        self.textField.textColor = UIColor.clearColor();
        self.textField.userInteractionEnabled = false;

        // Align the background TextView to where text appears in the TextField, so
        // that any placeholder will be in the correct position.
        self.textField.contentVerticalAlignment = UIControlContentVerticalAlignment.Top;
        self.textField.inset = UIEdgeInsets(
            top: self.textContainerInset.top,
            left: self.textContainerInset.left + self.textContainer.lineFragmentPadding,
            bottom: self.textContainerInset.bottom,
            right: self.textContainerInset.right
        );

        // The background TextField should use the same font (for the placeholder)
        self.textField.font = self.font;

        self.addSubview(textField);
        self.sendSubviewToBack(textField);
    }

    convenience init()
    {
        self.init(frame: CGRectZero, textContainer: nil)
    }

    override var font: UIFont?
    {
        didSet
        {
            // Keep the font of the TextView and background textField in sync
            self.textField.font = self.font;
        }
    }

    var placeholder: String? = nil
    {
        didSet
        {
            self.textField.placeholder = self.placeholder;
        }
    }

    override func layoutSubviews()
    {
        super.layoutSubviews()
        // Do not scroll the background textView
        self.textField.frame = CGRectMake(0, self.contentOffset.y, self.frame.width, self.frame.height);
    }

    // UITextViewDelegate - Note: If you replace delegate, your delegate must call this
    func scrollViewDidScroll(scrollView: UIScrollView)
    {
        // Do not scroll the background textView
        self.textField.frame = CGRectMake(0, self.contentOffset.y, self.frame.width, self.frame.height);
    }

    // UITextViewDelegate - Note: If you replace delegate, your delegate must call this
    func textViewDidChange(textView: UITextView)
    {
        // Updating the text in the background textView will cause the placeholder to 
        // appear/disappear (including any animations of that behavior - since the
        // textView is doing this itself).
        self.textField.text = self.text;
    }
}

- (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。

我建议使用SZTextView。

https://github.com/glaszig/SZTextView

从storyboard中添加默认的UITextView，然后将其自定义类更改为SZTextView，如下所示

然后您将在属性检查器中看到两个新选项

- (void)viewDidLoad {
    [super viewDidLoad];

    self.textViewEmpty = YES;

    // Text view
    self.textView = [[UITextView alloc] init];
    self.textView.translatesAutoresizingMaskIntoConstraints = NO; // For AutoLayout
    self.textView.delegate = self;
    self.textView.textColor = [UIColor grayColor];
    self.textView.text = @"Placeholder";

    // Add subview and constraints
}

#pragma mark - UITextView

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

    return YES;
}

- (void)textViewDidChange:(UITextView *)textView {
    if (textView.text.length > 0) {
        self.textViewEmpty = NO;
    } else {
        self.textViewEmpty = YES;
    }
}

- (BOOL)textViewShouldEndEditing:(UITextView *)textView {
    if (self.isTextViewEmpty) {
        textView.textColor = [UIColor lightGrayColor];
        textView.text = placeholderText;
    }

    return YES;
}