import UIKit
import RxSwift

@IBDesignable class TextViewWithPlaceholder: UITextView {
    
    //MARK: - Propertise
    @IBInspectable var placeholderText: String = ""
    
    let placeholderLabel = LocalizedUILabel()
    private let hidePlaceholderObserver = PublishSubject<Bool>()
    let disposeBag = DisposeBag()
    
    
    //MARK: - Did Move To Window
    override func didMoveToWindow() {
        super.didMoveToWindow()
        observeOnTextViewEditing()
        configurePlaceholder()
    }
    
    
    //MARK: - Observe On Text View Editing
    private func observeOnTextViewEditing() {
        rx.text.subscribe(onNext: { [weak self] selectedText in
            guard let self = self else { return }
            self.hidePlaceholderObserver.onNext((selectedText?.isEmpty ?? true) ? false : true)
            
        }).disposed(by: disposeBag)
    }
    
    
    //MARK: - Observe On Show Hide Placeholder
    private func configurePlaceholder() {
        hidePlaceholderObserver
            .bind(to: placeholderLabel.rx.isHidden)
            .disposed(by: disposeBag)
        
        placeholderLabel.text = placeholderText
        placeholderLabel.font = UIFont(name: "Poppins-Semibold", size: 16) ?? UIFont()
        placeholderLabel.textColor = .lightGray
        
        placeholderLabel.sizeToFit()
        placeholderLabel.frame.origin = CGPoint(x: 8, y: 8)
        addSubview(placeholderLabel)
    }
    
}

基于这里已经给出的一些很好的建议，我能够将以下轻量级的、与接口生成器兼容的UITextView子类组合在一起，它是:

包括可配置的占位符文本，样式就像UITextField一样。 不需要任何额外的子视图或约束。 不需要来自ViewController的任何委托或其他行为。 不需要任何通知。 保持占位符文本与查看字段文本属性的任何外部类完全分离。

任何改进建议都是受欢迎的，特别是如果有任何方法通过编程来获取iOS的占位符颜色，而不是硬编码它。

斯威夫特v5:

import UIKit
@IBDesignable class TextViewWithPlaceholder: UITextView {
    
    override var text: String! { // Ensures that the placeholder text is never returned as the field's text
        get {
            if showingPlaceholder {
                return "" // When showing the placeholder, there's no real text to return
            } else { return super.text }
        }
        set { super.text = newValue }
    }
    @IBInspectable var placeholderText: String = ""
    @IBInspectable var placeholderTextColor: UIColor = UIColor(red: 0.78, green: 0.78, blue: 0.80, alpha: 1.0) // Standard iOS placeholder color (#C7C7CD). See https://stackoverflow.com/questions/31057746/whats-the-default-color-for-placeholder-text-in-uitextfield
    private var showingPlaceholder: Bool = true // Keeps track of whether the field is currently showing a placeholder
    
    override func didMoveToWindow() {
        super.didMoveToWindow()
        if text.isEmpty {
            showPlaceholderText() // Load up the placeholder text when first appearing, but not if coming back to a view where text was already entered
        }
    }
    
    override func becomeFirstResponder() -> Bool {
        // If the current text is the placeholder, remove it
        if showingPlaceholder {
            text = nil
            textColor = nil // Put the text back to the default, unmodified color
            showingPlaceholder = false
        }
        return super.becomeFirstResponder()
    }
    
    override func resignFirstResponder() -> Bool {
        // If there's no text, put the placeholder back
        if text.isEmpty {
            showPlaceholderText()
        }
        return super.resignFirstResponder()
    }
    
    private func showPlaceholderText() {
        showingPlaceholder = true
        textColor = placeholderTextColor
        text = placeholderText
    }
}

我不知道为什么人们会把这个问题复杂化....这是相当直接和简单的。下面是UITextView的一个子类，它提供了所请求的功能。

- (void)customInit
{
    self.contentMode = UIViewContentModeRedraw;
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];
}

    - (void)textChanged:(NSNotification *)notification
    {
        if (notification.object == self) {
            if(self.textStorage.length != 0 || !self.textStorage.length) {
                [self setNeedsDisplay];
            }
        }
    }


    #pragma mark - Setters

    - (void)setPlaceholderText:(NSString *)placeholderText withFont:(UIFont *)font
    {
        self.placeholderText = placeholderText;
        self.placeholderTextFont = font;

    }



    - (void)drawRect:(CGRect)rect
    {
        [super drawRect:rect];
        [[UIColor lightGrayColor] setFill];

        if (self.textStorage.length != 0) {
            return;
        }

        CGRect inset = CGRectInset(rect, 8, 8);//Default rect insets for textView
        NSDictionary *attributes =  @{NSFontAttributeName: self.placeholderTextFont, NSForegroundColorAttributeName: [UIColor grayColor]};
        [self.placeholderText drawInRect:inset withAttributes:attributes];
    }`

import UIKit
import RxSwift

@IBDesignable class TextViewWithPlaceholder: UITextView {
    
    //MARK: - Propertise
    @IBInspectable var placeholderText: String = ""
    
    let placeholderLabel = LocalizedUILabel()
    private let hidePlaceholderObserver = PublishSubject<Bool>()
    let disposeBag = DisposeBag()
    
    
    //MARK: - Did Move To Window
    override func didMoveToWindow() {
        super.didMoveToWindow()
        observeOnTextViewEditing()
        configurePlaceholder()
    }
    
    
    //MARK: - Observe On Text View Editing
    private func observeOnTextViewEditing() {
        rx.text.subscribe(onNext: { [weak self] selectedText in
            guard let self = self else { return }
            self.hidePlaceholderObserver.onNext((selectedText?.isEmpty ?? true) ? false : true)
            
        }).disposed(by: disposeBag)
    }
    
    
    //MARK: - Observe On Show Hide Placeholder
    private func configurePlaceholder() {
        hidePlaceholderObserver
            .bind(to: placeholderLabel.rx.isHidden)
            .disposed(by: disposeBag)
        
        placeholderLabel.text = placeholderText
        placeholderLabel.font = UIFont(name: "Poppins-Semibold", size: 16) ?? UIFont()
        placeholderLabel.textColor = .lightGray
        
        placeholderLabel.sizeToFit()
        placeholderLabel.frame.origin = CGPoint(x: 8, y: 8)
        addSubview(placeholderLabel)
    }
    
}

我通过使用两个不同的文本视图来做到这一点:

一个在后台用作占位符。 一个在前台(具有透明背景)，用户实际输入。

其思想是，一旦用户开始在前景视图中输入内容，后台的占位符就会消失(如果用户删除了所有内容，则会重新出现)。因此，它的行为完全类似于单行文本字段的占位符。

这是我用的代码。注意，descriptionField是用户键入的字段，descriptionPlaceholder是后台的字段。

func textViewDidChange(descriptionField: UITextView) {
    if descriptionField.text.isEmpty == false {
        descriptionPlaceholder.text = ""
    } else {
        descriptionPlaceholder.text = descriptionPlaceholderText
    }
}

由于声誉问题，我不能发表评论。在@clearlight answer中增加一个委托需求。

func textViewDidBeginEditing(_ textView: UITextView) { 
        cell.placeholderLabel.isHidden = !textView.text.isEmpty
}

是需要

因为textViewDidChange不是第一次被调用