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
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
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。
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
}
}
}
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()
}
这里有一些东西可以被放到UIStackView中,它会使用内部高度约束来调整自己的大小。可能需要调整以适应特定的需求。
import UIKit
public protocol PlaceholderTextViewDelegate: class {
func placeholderTextViewTextChanged(_ textView: PlaceholderTextView, text: String)
}
public class PlaceholderTextView: UIView {
public weak var delegate: PlaceholderTextViewDelegate?
private var heightConstraint: NSLayoutConstraint?
public override init(frame: CGRect) {
self.allowsNewLines = true
super.init(frame: frame)
self.heightConstraint = self.heightAnchor.constraint(equalToConstant: 0)
self.heightConstraint?.isActive = true
self.addSubview(self.placeholderTextView)
self.addSubview(self.textView)
self.pinToCorners(self.placeholderTextView)
self.pinToCorners(self.textView)
self.updateHeight()
}
public override func didMoveToSuperview() {
super.didMoveToSuperview()
self.updateHeight()
}
private func pinToCorners(_ view: UIView) {
NSLayoutConstraint.activate([
view.leadingAnchor.constraint(equalTo: self.leadingAnchor),
view.trailingAnchor.constraint(equalTo: self.trailingAnchor),
view.topAnchor.constraint(equalTo: self.topAnchor),
view.bottomAnchor.constraint(equalTo: self.bottomAnchor)
])
}
// Accessors
public var text: String? {
didSet {
self.textView.text = text
self.textViewDidChange(self.textView)
self.updateHeight()
}
}
public var textColor: UIColor? {
didSet {
self.textView.textColor = textColor
self.updateHeight()
}
}
public var font: UIFont? {
didSet {
self.textView.font = font
self.placeholderTextView.font = font
self.updateHeight()
}
}
public override var tintColor: UIColor? {
didSet {
self.textView.tintColor = tintColor
self.placeholderTextView.tintColor = tintColor
}
}
public var placeholderText: String? {
didSet {
self.placeholderTextView.text = placeholderText
self.updateHeight()
}
}
public var placeholderTextColor: UIColor? {
didSet {
self.placeholderTextView.textColor = placeholderTextColor
self.updateHeight()
}
}
public var allowsNewLines: Bool
public required init?(coder _: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
private lazy var textView: UITextView = self.newTextView()
private lazy var placeholderTextView: UITextView = self.newTextView()
private func newTextView() -> UITextView {
let textView = UITextView()
textView.translatesAutoresizingMaskIntoConstraints = false
textView.isScrollEnabled = false
textView.delegate = self
textView.backgroundColor = .clear
return textView
}
private func updateHeight() {
let maxSize = CGSize(width: self.frame.size.width, height: .greatestFiniteMagnitude)
let textViewSize = self.textView.sizeThatFits(maxSize)
let placeholderSize = self.placeholderTextView.sizeThatFits(maxSize)
let maxHeight = ceil(CGFloat.maximum(textViewSize.height, placeholderSize.height))
self.heightConstraint?.constant = maxHeight
}
}
extension PlaceholderTextView: UITextViewDelegate {
public func textViewDidChangeSelection(_: UITextView) {
self.placeholderTextView.alpha = self.textView.text.isEmpty ? 1 : 0
self.updateHeight()
}
public func textViewDidChange(_: UITextView) {
self.delegate?.placeholderTextViewTextChanged(self, text: self.textView.text)
}
public func textView(_: UITextView, shouldChangeTextIn _: NSRange,
replacementText text: String) -> Bool {
let containsNewLines = text.rangeOfCharacter(from: .newlines)?.isEmpty == .some(false)
guard !containsNewLines || self.allowsNewLines else { return false }
return true
}
}
func setPlaceholder(){ var placeholderLabel = UILabel() placeholderLabel.text = "Describe your need..." placeholderLabel.font = UIFont.init(name: "Lato-Regular", size: 15.0) ?? UIFont.boldSystemFont(ofSize: 14.0) placeholderLabel.sizeToFit() descriptionTextView.addSubview(placeholderLabel) placeholderLabel.frame.origin = CGPoint(x: 5, y: (descriptionTextView.font?.pointSize)! / 2) placeholderLabel.textColor = UIColor.lightGray placeholderLabel.isHidden = !descriptionTextView.text.isEmpty } //Delegate Method. func textViewDidChange(_ textView: UITextView) { placeholderLabel.isHidden = !textView.text.isEmpty }
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