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。

其他回答

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。

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()
}

我们的解决方案避免了与UITextView文本和textColor属性的混淆,如果您要维护字符计数器,这是非常方便的。

很简单:

1)在Storyboard中创建一个与主UITextView属性相同的虚拟UITextView。将占位符文本分配给虚拟文本。

2)对齐两个uitextview的上、左、右边缘。

3)把假人放在主人的后面。

4)重写master的textViewDidChange(textView:)委托函数,如果master有0个字符,则显示dummy。否则,显示master。

这假设两个uitextview的背景都是透明的。如果没有,当有0个字符时,将假人放在上面,当有>个0个字符时,将它推到下面。您还必须交换响应器,以确保光标跟随正确的UITextView。

这就是我所做的。倾向于代码清晰和简单。我需要添加一个textView,将获得一些额外的笔记在我的应用程序。这额外的笔记可以创建或保存后修改。见下文。HTH。:)

class NotesTextView: UITextView {

    var placeholder = "" {
        didSet {
            showPlaceholder()
        }
    }
    
    // if the text is the placeholder, then assign a color fitting for a
    // placeholder text, else, assign it your color of choice.
    override var text: String! {
        didSet {
            textColor = text == placeholder ? .tertiaryLabel : .systemBlue
        }
    }
    
    
    override init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame, textContainer: textContainer)
        
        delegate = self
        //config your font and translateAutoResizingMaskIntoConstraints here
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    private func showPlaceholder() {
        text = placeholder
    }
    
    private func hidePlaceholder() {
        text = ""
    }
}

extension NotesTextView: UITextViewDelegate {
    func textViewDidBeginEditing(_ textView: UITextView) {
        if text == placeholder {
            hidePlaceholder()
        }
    }
    
    func textViewDidEndEditing(_ textView: UITextView) {
        if text.isEmpty {
            showPlaceholder()
        }
    }
}

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
    }

}