可能是UITextView占位符实现的最简单的开箱即用的解决方案，不会遭受:

使用UILabel而不是UITextView，这可能会有不同的表现 切换到和从占位符“UITextView”拷贝，将捕获第一个键入的字符将从主UITextView控件丢失 打乱主UITextView控件的文本内容，将占位符替换为空字符串或第一个键入的字符。边界情况是，如果用户输入占位符文本，一些建议的实现将把它作为一个占位符本身。

斯威夫特5:

import UIKit
import SnapKit
import RxSwift
import RxCocoa

class TextAreaView: UIView {
    let textArea = UITextView()
    let textAreaPlaceholder = UITextView()
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        commonSetup()
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        commonSetup()
    }
    
    private func commonSetup() {
        
        addSubview(textAreaPlaceholder)
        addSubview(textArea)
        
        textArea.isScrollEnabled = false
        textArea.delegate = self

        textAreaPlaceholder.isScrollEnabled = false
        textAreaPlaceholder.textColor = UIColor.lightGray
        
        textArea.snp.makeConstraints { make in
            make.top.bottom.leading.trailing.equalToSuperview()
        }

        textAreaPlaceholder.snp.makeConstraints { make in
            make.top.bottom.leading.trailing.equalTo(textArea.snp.top)
        }

        textAreaPlaceholder.text = "Placeholder"
        
        updatePlaceholder()
    }
    
    func updatePlaceholder() {
        if textArea.text.count > 0 {
            textArea.alpha = 1.0
        } else {
            textArea.alpha = 0.0
        }
    }
}

extension TextAreaView: UITextViewDelegate {
    func textViewDidChange(_ textView: UITextView) {
        updatePlaceholder()
    }
}

斯威夫特3.1

这个扩展为我工作得很好:https://github.com/devxoul/UITextView-Placeholder

下面是一个代码片段:

通过pod安装:

pod 'UITextView+Placeholder', '~> 1.2'

将它导入到类中

import UITextView_Placeholder

并添加占位符属性到您已经创建的UITextView

textView.placeholder = "Put some detail"

这是…… 这里是它的外观(第三个框是一个UITextView)

无需添加任何第三方库。只需使用下面的代码…

class SubmitReviewVC : UIViewController, UITextViewDelegate {

@IBOutlet var txtMessage : UITextView!
var lblPlaceHolder : UILabel!

override func viewDidLoad() {
    super.viewDidLoad()

    txtMessage.delegate = self
    lblPlaceHolder = UILabel()
    lblPlaceHolder.text = "Enter message..."
    lblPlaceHolder.font = UIFont.systemFont(ofSize: txtMessage.font!.pointSize)
    lblPlaceHolder.sizeToFit()
    txtMessage.addSubview(lblPlaceHolder)
    lblPlaceHolder.frame.origin = CGPoint(x: 5, y: (txtMessage.font?.pointSize)! / 2)
    lblPlaceHolder.textColor = UIColor.lightGray
    lblPlaceHolder.isHidden = !txtMessage.text.isEmpty
}

func textViewDidChange(_ textView: UITextView) {
    lblPlaceHolder.isHidden = !textView.text.isEmpty
}

}

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];
    }`

func setPlaceholder(){ var placeholderLabel = UILabel() placeholderLabel.text = "Describe your need..." placeholderLabel.font = UIFont.init(name: "Lato-Regular", size: 15.0) ?? UIFont.boldSystemFont(ofSize: 14.0) placeholderLabel.sizeToFit() descriptionTextView.addSubview(placeholderLabel) placeholderLabel.frame.origin = CGPoint(x: 5, y: (descriptionTextView.font?.pointSize)! / 2) placeholderLabel.textColor = UIColor.lightGray placeholderLabel.isHidden = !descriptionTextView.text.isEmpty } //Delegate Method. func textViewDidChange(_ textView: UITextView) { placeholderLabel.isHidden = !textView.text.isEmpty }

迅速:

以编程方式或通过Interface Builder添加你的文本视图，如果是最后一个，创建outlet:

@IBOutlet weak var yourTextView: UITextView!

请添加委托(UITextViewDelegate):

class ViewController: UIViewController, UITextViewDelegate {

在viewDidLoad方法中，添加如下内容:

override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

    yourTextView.delegate = self
    yourTextView.text = "Placeholder text goes right here..."
    yourTextView.textColor = UIColor.lightGray

现在让我来介绍一下神奇的部分，添加这个函数:

func textViewDidBeginEditing(_ textView: UITextView) {

    if yourTextView.textColor == UIColor.lightGray {
        yourTextView.text = ""
        yourTextView.textColor = UIColor.black
    }
}

请注意，这将在编辑开始时执行，在那里我们将检查条件来告知状态，使用color属性。 设置文本为nil我不建议。在此之后，我们将文本颜色设置为所需的颜色，在本例中为黑色。

现在也添加这个函数:

func textViewDidEndEditing(_ textView: UITextView) {

    if yourTextView.text == "" {

        yourTextView.text = "Placeholder text ..."
        yourTextView.textColor = UIColor.lightGray
    }
}

让我坚持一下，不要与零进行比较，我已经试过了，它不会起作用。然后我们将值设置回占位符样式，并将颜色设置回占位符颜色，因为这是在textViewDidBeginEditing中检查的条件。