另一个解决方案

import UIKit

protocol PlaceholderTextViewDelegate: class {

    func placeholderTextViewDidChangeText(_ text: String)
    func placeholderTextViewDidEndEditing(_ text: String)
}

final class PlaceholderTextView: UITextView {

    weak var notifier: PlaceholderTextViewDelegate?
    var ignoreEnterAction: Bool = true

    var placeholder: String? {
        didSet {
            text = placeholder
            selectedRange = NSRange(location: 0, length: 0)
        }
    }

    var placeholderColor = UIColor.lightGray {
        didSet {
            if text == placeholder {
                textColor = placeholderColor
            }
        }
    }
    var normalTextColor = UIColor.lightGray

    var placeholderFont = UIFont.sfProRegular(28)

    fileprivate var placeholderLabel: UILabel?

    // MARK: - LifeCycle

    override var text: String? {
        didSet {
            if text == placeholder {
                textColor = placeholderColor
            } else {
                textColor = normalTextColor
            }
        }
    }

    init() {
        super.init(frame: CGRect.zero, textContainer: nil)
        awakeFromNib()
    }

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

    override func awakeFromNib() {
        super.awakeFromNib()

        self.delegate = self
    }
}

extension PlaceholderTextView: UITextViewDelegate {

    // MARK: - UITextViewDelegate
    func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {

        if text == "" && textView.text == placeholder {
            return false
        }

        if let placeholder = placeholder,
            textView.text == placeholder,
            range.location <= placeholder.count {
            textView.text = ""
        }

        if ignoreEnterAction && text == "\n" {
            textView.resignFirstResponder()
            return false
        }
        return true
    }

    func textViewDidChange(_ textView: UITextView) {
        if let placeholder = placeholder {
            textView.text = textView.text.replacingOccurrences(of: placeholder, with: "")
        }

        if let placeholder = placeholder,
            text?.isEmpty == true {
            text = placeholder
            textColor = placeholderColor

            selectedRange = NSRange(location: 0, length: 0)
        } else {
            textColor = normalTextColor
        }

        notifier?.placeholderTextViewDidChangeText(textView.text)
    }

    func textViewDidChangeSelection(_ textView: UITextView) {
        if let placeholder = placeholder,
            text == placeholder {
            selectedRange = NSRange(location: 0, length: 0)
        }
    }

    func textViewDidEndEditing(_ textView: UITextView) {
        notifier?.placeholderTextViewDidEndEditing(textView.text)

        if let placeholder = placeholder,
            text?.isEmpty == true {
            text = placeholder
            textColor = placeholderColor
            selectedRange = NSRange(location: 0, length: 0)
        } else {
            textColor = normalTextColor
        }
    }
}

结果:

- (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;
}

修改占位符文本颜色最简单的方法是通过XCode故事板接口构建器。选择感兴趣的UITextField并打开右侧的标识检查器。单击User Defined Runtime Attributes中的加号，并添加一个新行，其中Key Path为_placeholderLabel。输入颜色和值到你想要的颜色。

我遵循了这个链接的代码。只有7个简单的步骤。它添加了一个UILabel的textView和隐藏/显示标签时，文本输入或从textView通过textView的textViewDidChangeSelection(_ textView: UITextView)委托方法。我将步骤放在代码上方的注释中。

// 1. make sure to include the UITextViewDelegate
class YourClass: UITextViewDelegate {

    @IBOutlet weak var textView : UITextView!

    // 2. create placeholder textLabel
    let placeHolderTextLabel: UILabel = {
        let placeholderLabel = UILabel()
        placeholderLabel.text = "Placeholder text..."
        placeholderLabel.sizeToFit()
        placeholderLabel.textColor = UIColor.lightGray
        return placeholderLabel
    }()

    override func viewDidLoad() {
        super.viewDidLoad()

        // 3. set textView delegate
        textView.delegate = self

        configurePlaceholderTextLabel()
    }


    func configurePlaceholderTextLabel() {

        // 4. add placeholder label to textView, set it's frame and font
        textView.addSubview(placeHolderTextLabel)
        placeHolderTextLabel.frame.origin = CGPoint(x: 5, y: (textView.font?.pointSize)! / 2)
        placeHolderTextLabel.font = UIFont.systemFont(ofSize: (textView.font?.pointSize)!)

        // 5. decide wether the placeHolderTextLabel is hidden or not depending on if there is or isn't text inside the textView
        placeHolderTextLabel.isHidden = !textView.text.isEmpty

    }

    // 6. implement textView delegate method to update the placeHolderTextLabel when the text is changed
    func textViewDidChangeSelection(_ textView: UITextView) {

        // 7. decide wether the placeHolderTextLabel is hidden or not depending on if there is or isn't text inside the textView when text in textView is changed
        placeHolderTextLabel.isHidden = !textView.text.isEmpty
    }

}

在看完所有答案后，我意识到我需要一些简单的，同时可重用的东西，这样我就可以在我的项目中为所有uitextview添加相同的功能。最后我得到了以下代码:

extension UITextView {

// MARK: TextView PlaceHolderLabel Setup

func createPlaceHolderLabel(with text: String) {
    let lbl = UILabel()
    self.addSubview(lbl)

// Add your constraints here

    lbl.text = text
    lbl.textColor = .lightGray
}

// My Textview contains only one UILabel, and for my use case the below code works, tweak it according to your use case

// Lastly two methods to toggle between show and hide the placeholder label

func hidePlaceHolderLabel() {
    guard let lbl = self.subviews.first(where: { $0 is UILabel }) else { return }
    lbl.isHidden = true
}

func showPlaceHolderLabel() {
    guard let lbl = self.subviews.first(where: { $0 is UILabel }) else { return }
    lbl.isHidden = false
}

}

当UILabel作为子视图添加到UITextView时，textView游标位置和UILabel位置将不匹配，因此在占位符文本之前留下一个空间

class ViewController: UIViewController, UITextViewDelegate {
    var textView: UITextView!

override func viewDidLoad() {
    super.viewDidLoad()
    view.addSubview(textView)
    // Also setup textView constraints as per your need
    // Add placeholder to your textView
    // Leave one space before placeholder string
    textView.createPlaceHolderLabel(with: " Address")
    textView.delegate = self
}

然后在textViewdidChange方法中添加以下代码

func textViewDidChange(_ textView: UITextView) {
    if textView.text.isEmpty {
        textView.showPlaceHolderLabel()
    } else {
        textView.hidePlaceHolderLabel()
    }
}

它可以在所有uitextview中重用。

- (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。