我的应用程序使用UITextView。现在我想让UITextView有一个占位符,类似于你可以为UITextField设置的占位符。
如何做到这一点?
我的应用程序使用UITextView。现在我想让UITextView有一个占位符,类似于你可以为UITextField设置的占位符。
如何做到这一点?
当前回答
- (void)textViewDidChange:(UITextView *)textView
{
placeholderLabel.hidden = YES;
}
在textview上放一个标签。
其他回答
在swift 5。工作很好。
class BaseTextView: UITextView {
// MARK: - Views
private var placeholderLabel: UIlabel!
// MARK: - Init
override init(frame: CGRect, textContainer: NSTextContainer?) {
super.init(frame: frame, textContainer: textContainer)
setupUI()
startupSetup()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
setupUI()
startupSetup()
}
deinit {
NotificationCenter.default.removeObserver(self)
}
}
// MARK: - Setup UI
private extension BaseTextView {
func setupUI() {
addPlaceholderLabel()
textColor = .textColor
}
func addPlaceholderLabel() {
placeholderLabel = BaseLabel(frame: .zero)
placeholderLabel.translatesAutoresizingMaskIntoConstraints = false
insertSubview(placeholderLabel, at: 0)
placeholderLabel.alpha = 0
placeholderLabel.numberOfLines = 0
placeholderLabel.backgroundColor = .clear
placeholderLabel.textColor = .lightTextColor
placeholderLabel.lineBreakMode = .byWordWrapping
placeholderLabel.isUserInteractionEnabled = false
placeholderLabel.font = UIFont.openSansSemibold.withSize(12)
placeholderLabel.topAnchor.constraint(equalTo: topAnchor, constant: 8).isActive = true
placeholderLabel.leftAnchor.constraint(equalTo: leftAnchor, constant: 5).isActive = true
placeholderLabel.rightAnchor.constraint(lessThanOrEqualTo: rightAnchor, constant: -8).isActive = true
placeholderLabel.bottomAnchor.constraint(lessThanOrEqualTo: bottomAnchor, constant: -8).isActive = true
}
}
// MARK: - Startup
private extension BaseTextView {
func startupSetup() {
addObservers()
textChanged(nil)
font = UIFont.openSansSemibold.withSize(12)
}
func addObservers() {
NotificationCenter.default.addObserver(self, selector: #selector(textChanged(_:)), name: UITextView.textDidChangeNotification, object: nil)
}
}
// MARK: - Actions
private extension BaseTextView {
@objc func textChanged(_ sender: Notification?) {
UIView.animate(withDuration: 0.2) {
self.placeholderLabel.alpha = self.text.count == 0 ? 1 : 0
}
}
}
// MARK: - Public methods
extension BaseTextView {
public func setPlaceholder(_ placeholder: String) {
placeholderLabel.text = placeholder
}
}
简单地创建UITextView的@IBDesignable子类:
@IBDesignable class AttributedTextView: UITextView {
private let placeholderLabel = UILabel()
@IBInspectable var placeholder: String = "" {
didSet {
setupPlaceholderLabelIfNeeded()
textViewDidChange()
}
}
override var text: String! {
didSet {
textViewDidChange()
}
}
//MARK: - Initialization
override func awakeFromNib() {
super.awakeFromNib()
setupPlaceholderLabelIfNeeded()
NotificationCenter.default.addObserver(self, selector: #selector(textViewDidChange), name: .UITextViewTextDidChange, object: nil)
}
//MARK: - Deinitialization
deinit {
NotificationCenter.default.removeObserver(self)
}
//MARK: - Internal
func textViewDidChange() {
placeholderLabel.isHidden = !text.isEmpty
layoutIfNeeded()
}
//MARK: - Private
private func setupPlaceholderLabelIfNeeded() {
placeholderLabel.removeFromSuperview()
placeholderLabel.frame = CGRect(x: 0, y: 8, width: frame.size.width, height: 0)
placeholderLabel.textColor = UIColor.lightGray
placeholderLabel.text = placeholder
placeholderLabel.sizeToFit()
insertSubview(placeholderLabel, at: 0)
}
}
然后在标识检查器中设置占位符:
另一个答案是:
https://github.com/gcamp/GCPlaceholderTextView
改变类UITextView在IB到GCPlaceholderTextView 并设置占位符属性
你能做的是在文本属性中设置文本视图的初始值,并将textColor更改为[UIColor grayColor]或类似的东西。然后,每当文本视图变为可编辑时,清除文本并显示游标,如果文本字段再次为空,则将占位符文本放回。根据需要将颜色更改为[UIColor blackColor]。
它与UITextField中的占位符功能不完全相同,但很接近。
我通读了所有这些,但提出了一个非常简短的Swift 3解决方案,在我的所有测试中都有效。它可以更一般化一点,但过程很简单。这是整个东西,我称之为“TextViewWithPlaceholder”。
import UIKit
class TextViewWithPlaceholder: UITextView {
public var placeholder: String?
public var placeholderColor = UIColor.lightGray
private var placeholderLabel: UILabel?
// Set up notification listener when created from a XIB or storyboard.
// You can also set up init() functions if you plan on creating
// these programmatically.
override func awakeFromNib() {
super.awakeFromNib()
NotificationCenter.default.addObserver(self,
selector: #selector(TextViewWithPlaceholder.textDidChangeHandler(notification:)),
name: .UITextViewTextDidChange,
object: self)
placeholderLabel = UILabel()
placeholderLabel?.alpha = 0.85
placeholderLabel?.textColor = placeholderColor
}
// By using layoutSubviews, you can size and position the placeholder
// more accurately. I chose to hard-code the size of the placeholder
// but you can combine this with other techniques shown in previous replies.
override func layoutSubviews() {
super.layoutSubviews()
placeholderLabel?.textColor = placeholderColor
placeholderLabel?.text = placeholder
placeholderLabel?.frame = CGRect(x: 6, y: 4, width: self.bounds.size.width-16, height: 24)
if text.isEmpty {
addSubview(placeholderLabel!)
bringSubview(toFront: placeholderLabel!)
} else {
placeholderLabel?.removeFromSuperview()
}
}
// Whenever the text changes, just trigger a new layout pass.
func textDidChangeHandler(notification: Notification) {
layoutSubviews()
}
}