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
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。
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)
还有一个解决方案(Swift 3):
import UIKit
protocol PlaceholderTextViewDelegate {
func placeholderTextViewDidChangeText(_ text:String)
func placeholderTextViewDidEndEditing(_ text:String)
}
final class PlaceholderTextView: UITextView {
var notifier:PlaceholderTextViewDelegate?
var placeholder: String? {
didSet {
placeholderLabel?.text = placeholder
}
}
var placeholderColor = UIColor.lightGray
var placeholderFont = UIFont.appMainFontForSize(14.0) {
didSet {
placeholderLabel?.font = placeholderFont
}
}
fileprivate var placeholderLabel: UILabel?
// MARK: - LifeCycle
init() {
super.init(frame: CGRect.zero, textContainer: nil)
awakeFromNib()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
override func awakeFromNib() {
super.awakeFromNib()
self.delegate = self
NotificationCenter.default.addObserver(self, selector: #selector(PlaceholderTextView.textDidChangeHandler(notification:)), name: .UITextViewTextDidChange, object: nil)
placeholderLabel = UILabel()
placeholderLabel?.textColor = placeholderColor
placeholderLabel?.text = placeholder
placeholderLabel?.textAlignment = .left
placeholderLabel?.numberOfLines = 0
}
override func layoutSubviews() {
super.layoutSubviews()
placeholderLabel?.font = placeholderFont
var height:CGFloat = placeholderFont.lineHeight
if let data = placeholderLabel?.text {
let expectedDefaultWidth:CGFloat = bounds.size.width
let fontSize:CGFloat = placeholderFont.pointSize
let textView = UITextView()
textView.text = data
textView.font = UIFont.appMainFontForSize(fontSize)
let sizeForTextView = textView.sizeThatFits(CGSize(width: expectedDefaultWidth,
height: CGFloat.greatestFiniteMagnitude))
let expectedTextViewHeight = sizeForTextView.height
if expectedTextViewHeight > height {
height = expectedTextViewHeight
}
}
placeholderLabel?.frame = CGRect(x: 5, y: 0, width: bounds.size.width - 16, height: height)
if text.isEmpty {
addSubview(placeholderLabel!)
bringSubview(toFront: placeholderLabel!)
} else {
placeholderLabel?.removeFromSuperview()
}
}
func textDidChangeHandler(notification: Notification) {
layoutSubviews()
}
}
extension PlaceholderTextView : UITextViewDelegate {
// MARK: - UITextViewDelegate
func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
if(text == "\n") {
textView.resignFirstResponder()
return false
}
return true
}
func textViewDidChange(_ textView: UITextView) {
notifier?.placeholderTextViewDidChangeText(textView.text)
}
func textViewDidEndEditing(_ textView: UITextView) {
notifier?.placeholderTextViewDidEndEditing(textView.text)
}
}
结果
浮动的占位符
将占位符标签放置在文本视图之上,通过跟踪文本视图字符计数的变化来设置其字体、颜色和管理占位符可见性,这是简单、安全且可靠的。
斯威夫特5:
class NotesViewController : UIViewController {
@IBOutlet var textView : UITextView!
var placeholderLabel : UILabel!
override func viewDidLoad() {
super.viewDidLoad()
textView.delegate = self
placeholderLabel = UILabel()
placeholderLabel.text = "Enter some text..."
placeholderLabel.font = .italicSystemFont(ofSize: (textView.font?.pointSize)!)
placeholderLabel.sizeToFit()
textView.addSubview(placeholderLabel)
placeholderLabel.frame.origin = CGPoint(x: 5, y: (textView.font?.pointSize)! / 2)
placeholderLabel.textColor = .tertiaryLabel
placeholderLabel.isHidden = !textView.text.isEmpty
}
}
extension NotesViewController : UITextViewDelegate {
func textViewDidChange(_ textView: UITextView) {
placeholderLabel.isHidden = !textView.text.isEmpty
}
}
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