斯威夫特5.2

独立的类

如果你想要一个类，你可以在任何地方使用，因为它是自包含的

import UIKit
class PlaceHolderTextView:UITextView, UITextViewDelegate{
var placeholderText = "placeholderText"

override func willMove(toSuperview newSuperview: UIView?) {
    textColor = .lightText
    delegate = self
}

func textViewDidBeginEditing(_ textView: UITextView) {
    if textView.text == placeholderText{
        placeholderText = textView.text
        textView.text = ""
        textView.textColor = .darkText
    }
}

func textViewDidEndEditing(_ textView: UITextView) {
    if textView.text == ""{
        textView.text = placeholderText
        textColor = .lightText
    }
}    
}

这里的关键是willMove(toSuperView:)函数，因为它允许你在添加到另一个视图的层次结构之前设置视图(类似于ViewControllers中的viewDidLoad/viewWillAppear)

这是我准备使用的解决方案，如果您正在处理多个文本视图

func textViewShouldBeginEditing(textView: UITextView) -> Bool {        
    // Set cursor to the beginning if placeholder is set
    if textView.textColor == UIColor.lightGrayColor() {
        textView.selectedTextRange = textView.textRangeFromPosition(textView.beginningOfDocument, toPosition: textView.beginningOfDocument)
    }

    return true
}

func textView(textView: UITextView, shouldChangeTextInRange range: NSRange, replacementText text: String) -> Bool {
    // Remove placeholder
    if textView.textColor == UIColor.lightGrayColor() && text.characters.count > 0 {
        textView.text = ""
        textView.textColor = UIColor.blackColor()
    }

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

    return true
}

func textViewDidChange(textView: UITextView) {
    // Set placeholder if text is empty
    if textView.text.isEmpty {
        textView.text = NSLocalizedString("Hint", comment: "hint")
        textView.textColor = UIColor.lightGrayColor()
        textView.selectedTextRange = textView.textRangeFromPosition(textView.beginningOfDocument, toPosition: textView.beginningOfDocument)
    }
}

func textViewDidChangeSelection(textView: UITextView) {
    // Set cursor to the beginning if placeholder is set
    let firstPosition = textView.textRangeFromPosition(textView.beginningOfDocument, toPosition: textView.beginningOfDocument)

    // Do not change position recursively
    if textView.textColor == UIColor.lightGrayColor() && textView.selectedTextRange != firstPosition {
        textView.selectedTextRange = firstPosition
    }
}

我相信这是一个非常干净的解决方案。它在实际文本视图下面添加了一个虚拟文本视图，并根据实际文本视图中的文本显示或隐藏它:

import Foundation
import UIKit

class TextViewWithPlaceholder: UITextView {

    private var placeholderTextView: UITextView = UITextView()

    var placeholder: String? {
        didSet {
            placeholderTextView.text = placeholder
        }
    }

    override var text: String! {
        didSet {
            placeholderTextView.isHidden = text.isEmpty == false
        }
    }

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

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

    private func commonInit() {
        applyCommonTextViewAttributes(to: self)
        configureMainTextView()
        addPlaceholderTextView()
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(textDidChange),
                                               name: UITextView.textDidChangeNotification,
                                               object: nil)
    }

    func addPlaceholderTextView() {
        applyCommonTextViewAttributes(to: placeholderTextView)
        configurePlaceholderTextView()
        insertSubview(placeholderTextView, at: 0)
    }

    private func applyCommonTextViewAttributes(to textView: UITextView) {
        textView.translatesAutoresizingMaskIntoConstraints = false
        textView.textContainer.lineFragmentPadding = 0
        textView.textContainerInset = UIEdgeInsets(top: 10,
                                                   left: 10,
                                                   bottom: 10,
                                                   right: 10)
    }

    private func configureMainTextView() {
        // Do any configuration of the actual text view here
    }

    private func configurePlaceholderTextView() {
        placeholderTextView.text = placeholder
        placeholderTextView.font = font
        placeholderTextView.textColor = UIColor.lightGray
        placeholderTextView.frame = bounds
        placeholderTextView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        placeholderTextView.frame = bounds
    }

    @objc func textDidChange() {
        placeholderTextView.isHidden = !text.isEmpty
    }

}

以下是我解决这个问题的方法(Swift 4):

这个想法是做出最简单的解决方案，允许使用不同颜色的占位符，调整占位符大小，不会覆盖委托，同时保持所有UITextView函数正常工作。

import UIKit

class PlaceholderTextView: UITextView {
    var placeholderColor: UIColor = .lightGray
    var defaultTextColor: UIColor = .black

    private var isShowingPlaceholder = false {
        didSet {
            if isShowingPlaceholder {
                text = placeholder
                textColor = placeholderColor
            } else {
                textColor = defaultTextColor
            }
        }
    }

    var placeholder: String? {
        didSet {
            isShowingPlaceholder = !hasText
        }
    }

    @objc private func textViewDidBeginEditing(notification: Notification) {
        textColor = defaultTextColor
        if isShowingPlaceholder { text = nil }
    }

    @objc private func textViewDidEndEditing(notification: Notification) {
        isShowingPlaceholder = !hasText
    }

    // MARK: - Construction -
    override init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame, textContainer: textContainer)
        setup()
    }

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

    private func setup() {
        NotificationCenter.default.addObserver(self, selector: #selector(textViewDidBeginEditing(notification:)), name: UITextView.textDidBeginEditingNotification, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(textViewDidEndEditing(notification:)), name: UITextView.textDidEndEditingNotification, object: nil)
    }

    // MARK: - Destruction -
    deinit { NotificationCenter.default.removeObserver(self) }
}

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。

没有这样的属性在ios添加占位符直接在TextView，而你可以添加一个标签和显示/隐藏在TextView的变化。SWIFT 2.0，确保实现textviewdelegate

func textViewDidChange(TextView: UITextView)
{

 if  txtShortDescription.text == ""
    {
        self.lblShortDescription.hidden = false
    }
    else
    {
        self.lblShortDescription.hidden = true
    }

}