如何在UITextView中添加占位符,类似于你可以为UITextField设置的占位符,在Swift中?


当前回答

在视图加载中设置值

    txtVw!.autocorrectionType = UITextAutocorrectionType.No
    txtVw!.text = "Write your Placeholder"
    txtVw!.textColor = UIColor.lightGrayColor()



func textViewDidBeginEditing(textView: UITextView) {
    if (txtVw?.text == "Write your Placeholder")

    {
        txtVw!.text = nil
        txtVw!.textColor = UIColor.blackColor()
    }
}

func textViewDidEndEditing(textView: UITextView) {
    if txtVw!.text.isEmpty
    {
        txtVw!.text = "Write your Placeholder"
        txtVw!.textColor = UIColor.lightGrayColor()
    }
    textView.resignFirstResponder()
}

其他回答

迅速:

添加你的TextView @IBOutlet:

@IBOutlet weak var txtViewMessage: UITextView!

在viewWillAppear方法中,添加以下内容:

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    txtViewMessage.delegate = self    // Give TextViewMessage delegate Method
    
    txtViewMessage.text = "Place Holder Name"
    txtViewMessage.textColor = UIColor.lightGray
}

请添加委托使用扩展(UITextViewDelegate):

// MARK: - UITextViewDelegate
extension ViewController: UITextViewDelegate {

    func textViewDidBeginEditing(_ textView: UITextView) {

        if !txtViewMessage.text!.isEmpty && txtViewMessage.text! == "Place Holder Name" {
            txtViewMessage.text = ""
            txtViewMessage.textColor = UIColor.black
        }
    }

    func textViewDidEndEditing(_ textView: UITextView) {
    
        if txtViewMessage.text.isEmpty {
            txtViewMessage.text = "Place Holder Name"
            txtViewMessage.textColor = UIColor.lightGray
        }
    }
}

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
}

}

文本视图委托方法

使用这两个委托方法,并在类中编写UITextViewDelegate

func textViewDidBeginEditing(_ textView: UITextView) {
    if (commentsTextView.text == "Type Your Comments")
    {
        commentsTextView.text = nil
        commentsTextView.textColor = UIColor.darkGray
    }
}

func textViewDidEndEditing(_ textView: UITextView) {
    if commentsTextView.text.isEmpty
    {
        commentsTextView.text = "Type Your Comments"
        commentsTextView.textColor = UIColor.darkGray
    }
    textView.resignFirstResponder()
}

我试着用clearlight的答案来简化代码。

extension UITextView{

    func setPlaceholder() {

        let placeholderLabel = UILabel()
        placeholderLabel.text = "Enter some text..."
        placeholderLabel.font = UIFont.italicSystemFont(ofSize: (self.font?.pointSize)!)
        placeholderLabel.sizeToFit()
        placeholderLabel.tag = 222
        placeholderLabel.frame.origin = CGPoint(x: 5, y: (self.font?.pointSize)! / 2)
        placeholderLabel.textColor = UIColor.lightGray
        placeholderLabel.isHidden = !self.text.isEmpty

        self.addSubview(placeholderLabel)
    }

    func checkPlaceholder() {
        let placeholderLabel = self.viewWithTag(222) as! UILabel
        placeholderLabel.isHidden = !self.text.isEmpty
    }

}

使用

override func viewDidLoad() {
    textView.delegate = self
    textView.setPlaceholder()
}

func textViewDidChange(_ textView: UITextView) {
    textView.checkPlaceholder()
}

在swift2.2:

public class CustomTextView: UITextView {

private struct Constants {
    static let defaultiOSPlaceholderColor = UIColor(red: 0.0, green: 0.0, blue: 0.0980392, alpha: 0.22)
}
private let placeholderLabel: UILabel = UILabel()

private var placeholderLabelConstraints = [NSLayoutConstraint]()

@IBInspectable public var placeholder: String = "" {
    didSet {
        placeholderLabel.text = placeholder
    }
}

@IBInspectable public var placeholderColor: UIColor = CustomTextView.Constants.defaultiOSPlaceholderColor {
    didSet {
        placeholderLabel.textColor = placeholderColor
    }
}

override public var font: UIFont! {
    didSet {
        placeholderLabel.font = font
    }
}

override public var textAlignment: NSTextAlignment {
    didSet {
        placeholderLabel.textAlignment = textAlignment
    }
}

override public var text: String! {
    didSet {
        textDidChange()
    }
}

override public var attributedText: NSAttributedString! {
    didSet {
        textDidChange()
    }
}

override public var textContainerInset: UIEdgeInsets {
    didSet {
        updateConstraintsForPlaceholderLabel()
    }
}

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

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

private func commonInit() {
    NSNotificationCenter.defaultCenter().addObserver(self,
                                                     selector: #selector(textDidChange),
                                                     name: UITextViewTextDidChangeNotification,
                                                     object: nil)

    placeholderLabel.font = font
    placeholderLabel.textColor = placeholderColor
    placeholderLabel.textAlignment = textAlignment
    placeholderLabel.text = placeholder
    placeholderLabel.numberOfLines = 0
    placeholderLabel.backgroundColor = UIColor.clearColor()
    placeholderLabel.translatesAutoresizingMaskIntoConstraints = false
    addSubview(placeholderLabel)
    updateConstraintsForPlaceholderLabel()
}

private func updateConstraintsForPlaceholderLabel() {
    var newConstraints = NSLayoutConstraint.constraintsWithVisualFormat("H:|-(\(textContainerInset.left + textContainer.lineFragmentPadding))-[placeholder]",
                                                                        options: [],
                                                                        metrics: nil,
                                                                        views: ["placeholder": placeholderLabel])
    newConstraints += NSLayoutConstraint.constraintsWithVisualFormat("V:|-(\(textContainerInset.top))-[placeholder]",
                                                                     options: [],
                                                                     metrics: nil,
                                                                     views: ["placeholder": placeholderLabel])
    newConstraints.append(NSLayoutConstraint(
        item: placeholderLabel,
        attribute: .Width,
        relatedBy: .Equal,
        toItem: self,
        attribute: .Width,
        multiplier: 1.0,
        constant: -(textContainerInset.left + textContainerInset.right + textContainer.lineFragmentPadding * 2.0)
        ))
    removeConstraints(placeholderLabelConstraints)
    addConstraints(newConstraints)
    placeholderLabelConstraints = newConstraints
}

@objc private func textDidChange() {
    placeholderLabel.hidden = !text.isEmpty
}

public override func layoutSubviews() {
    super.layoutSubviews()
    placeholderLabel.preferredMaxLayoutWidth = textContainer.size.width - textContainer.lineFragmentPadding * 2.0
}

deinit {
    NSNotificationCenter.defaultCenter().removeObserver(self,
                                                        name: UITextViewTextDidChangeNotification,
                                                        object: nil)
}

}

在swift3:

import UIKit

类 CustomTextView: { UITextView

private struct Constants {
    static let defaultiOSPlaceholderColor = UIColor(red: 0.0, green: 0.0, blue: 0.0980392, alpha: 0.22)
}
private let placeholderLabel: UILabel = UILabel()

private var placeholderLabelConstraints = [NSLayoutConstraint]()

@IBInspectable public var placeholder: String = "" {
    didSet {
        placeholderLabel.text = placeholder
    }
}

@IBInspectable public var placeholderColor: UIColor = CustomTextView.Constants.defaultiOSPlaceholderColor {
    didSet {
        placeholderLabel.textColor = placeholderColor
    }
}

override public var font: UIFont! {
    didSet {
        placeholderLabel.font = font
    }
}

override public var textAlignment: NSTextAlignment {
    didSet {
        placeholderLabel.textAlignment = textAlignment
    }
}

override public var text: String! {
    didSet {
        textDidChange()
    }
}

override public var attributedText: NSAttributedString! {
    didSet {
        textDidChange()
    }
}

override public var textContainerInset: UIEdgeInsets {
    didSet {
        updateConstraintsForPlaceholderLabel()
    }
}

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

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

private func commonInit() {
    NotificationCenter.default.addObserver(self,
                                                     selector: #selector(textDidChange),
                                                     name: NSNotification.Name.UITextViewTextDidChange,
                                                     object: nil)

    placeholderLabel.font = font
    placeholderLabel.textColor = placeholderColor
    placeholderLabel.textAlignment = textAlignment
    placeholderLabel.text = placeholder
    placeholderLabel.numberOfLines = 0
    placeholderLabel.backgroundColor = UIColor.clear
    placeholderLabel.translatesAutoresizingMaskIntoConstraints = false
    addSubview(placeholderLabel)
    updateConstraintsForPlaceholderLabel()
}

private func updateConstraintsForPlaceholderLabel() {
    var newConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:|-(\(textContainerInset.left + textContainer.lineFragmentPadding))-[placeholder]",
        options: [],
        metrics: nil,
        views: ["placeholder": placeholderLabel])
    newConstraints += NSLayoutConstraint.constraints(withVisualFormat: "V:|-(\(textContainerInset.top))-[placeholder]",
        options: [],
        metrics: nil,
        views: ["placeholder": placeholderLabel])
    newConstraints.append(NSLayoutConstraint(
        item: placeholderLabel,
        attribute: .width,
        relatedBy: .equal,
        toItem: self,
        attribute: .width,
        multiplier: 1.0,
        constant: -(textContainerInset.left + textContainerInset.right + textContainer.lineFragmentPadding * 2.0)
    ))
    removeConstraints(placeholderLabelConstraints)
    addConstraints(newConstraints)
    placeholderLabelConstraints = newConstraints
}

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

public override func layoutSubviews() {
    super.layoutSubviews()
    placeholderLabel.preferredMaxLayoutWidth = textContainer.size.width - textContainer.lineFragmentPadding * 2.0
}

deinit {
    NotificationCenter.default.removeObserver(self,
                                                        name: NSNotification.Name.UITextViewTextDidChange,
                                                        object: nil)
}

}

我用swift写了一个类。您需要在需要的时候导入这个类。