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
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)
其他回答
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。
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
}
}
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
}
}
迅速的回答
这是一个自定义类,用于动画占位符。
class CustomTextView: UITextView {
// MARK: - public
public var placeHolderText: String? = "Enter Reason.."
public lazy var placeHolderLabel: UILabel! = {
let placeHolderLabel = UILabel(frame: .zero)
placeHolderLabel.numberOfLines = 0
placeHolderLabel.backgroundColor = .clear
placeHolderLabel.alpha = 0.5
return placeHolderLabel
}()
// MARK: - Init
override init(frame: CGRect, textContainer: NSTextContainer?) {
super.init(frame: frame, textContainer: textContainer)
enableNotifications()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
enableNotifications()
}
func setup() {
placeHolderLabel.frame = CGRect(x: 8, y: 8, width: self.bounds.size.width - 16, height: 15)
placeHolderLabel.sizeToFit()
}
// MARK: - Cycle
override func awakeFromNib() {
super.awakeFromNib()
textContainerInset = UIEdgeInsets(top: 8, left: 5, bottom: 8, right: 8)
returnKeyType = .done
addSubview(placeHolderLabel)
placeHolderLabel.frame = CGRect(x: 8, y: 8, width: self.bounds.size.width - 16, height: 15)
placeHolderLabel.textColor = textColor
placeHolderLabel.font = font
placeHolderLabel.text = placeHolderText
bringSubviewToFront(placeHolderLabel)
}
override func layoutSubviews() {
super.layoutSubviews()
setup()
}
// MARK: - Notifications
private func enableNotifications() {
NotificationCenter.default.addObserver(self, selector: #selector(textDidChangeNotification(_:)), name: UITextView.textDidChangeNotification , object: nil)
}
@objc func textDidChangeNotification(_ notify: Notification) {
guard self == notify.object as? UITextView else { return }
guard placeHolderText != nil else { return }
UIView.animate(withDuration: 0.25, animations: {
self.placeHolderLabel.alpha = (self.text.count == 0) ? 0.5 : 0
}, completion: nil)
}
}
这是我用来完成这项工作的方法。
@IBDesignable class UIPlaceholderTextView: UITextView {
var placeholderLabel: UILabel?
override init(frame: CGRect, textContainer: NSTextContainer?) {
super.init(frame: frame, textContainer: textContainer)
sharedInit()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
sharedInit()
}
override func prepareForInterfaceBuilder() {
sharedInit()
}
func sharedInit() {
refreshPlaceholder()
NotificationCenter.default.addObserver(self, selector: #selector(textChanged), name: UITextView.textDidChangeNotification, object: nil)
}
@IBInspectable var placeholder: String? {
didSet {
refreshPlaceholder()
}
}
@IBInspectable var placeholderColor: UIColor? = .darkGray {
didSet {
refreshPlaceholder()
}
}
@IBInspectable var placeholderFontSize: CGFloat = 14 {
didSet {
refreshPlaceholder()
}
}
func refreshPlaceholder() {
if placeholderLabel == nil {
placeholderLabel = UILabel()
let contentView = self.subviews.first ?? self
contentView.addSubview(placeholderLabel!)
placeholderLabel?.translatesAutoresizingMaskIntoConstraints = false
placeholderLabel?.leftAnchor.constraint(equalTo: contentView.leftAnchor, constant: textContainerInset.left + 4).isActive = true
placeholderLabel?.rightAnchor.constraint(equalTo: contentView.rightAnchor, constant: textContainerInset.right + 4).isActive = true
placeholderLabel?.topAnchor.constraint(equalTo: contentView.topAnchor, constant: textContainerInset.top).isActive = true
placeholderLabel?.bottomAnchor.constraint(lessThanOrEqualTo: contentView.bottomAnchor, constant: textContainerInset.bottom).isActive = true
}
placeholderLabel?.text = placeholder
placeholderLabel?.textColor = placeholderColor
placeholderLabel?.font = UIFont.systemFont(ofSize: placeholderFontSize)
}
@objc func textChanged() {
if self.placeholder?.isEmpty ?? true {
return
}
UIView.animate(withDuration: 0.25) {
if self.text.isEmpty {
self.placeholderLabel?.alpha = 1.0
} else {
self.placeholderLabel?.alpha = 0.0
}
}
}
override var text: String! {
didSet {
textChanged()
}
}
}
我知道有很多类似的方法,但这个方法的好处是:
在IB中设置占位符文本、字体大小和颜色。 在IB中不再显示“滚动视图有不明确的可滚动内容”的警告。 添加动画显示/隐藏占位符。
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