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
无需添加任何第三方库。只需使用下面的代码…
class SubmitReviewVC : UIViewController, UITextViewDelegate {
@IBOutlet var txtMessage : UITextView!
var lblPlaceHolder : UILabel!
override func viewDidLoad() {
super.viewDidLoad()
txtMessage.delegate = self
lblPlaceHolder = UILabel()
lblPlaceHolder.text = "Enter message..."
lblPlaceHolder.font = UIFont.systemFont(ofSize: txtMessage.font!.pointSize)
lblPlaceHolder.sizeToFit()
txtMessage.addSubview(lblPlaceHolder)
lblPlaceHolder.frame.origin = CGPoint(x: 5, y: (txtMessage.font?.pointSize)! / 2)
lblPlaceHolder.textColor = UIColor.lightGray
lblPlaceHolder.isHidden = !txtMessage.text.isEmpty
}
func textViewDidChange(_ textView: UITextView) {
lblPlaceHolder.isHidden = !textView.text.isEmpty
}
}
其他回答
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。
协议版本的clearlight的答案上面,因为协议是伟大的。随便放哪都行。扣篮!
extension UITextViewPlaceholder where Self: UIViewController {
// Use this in ViewController's ViewDidLoad method.
func addPlaceholder(text: String, toTextView: UITextView, font: UIFont? = nil) {
placeholderLabel = UILabel()
placeholderLabel.text = text
placeholderLabel.font = font ?? UIFont.italicSystemFont(ofSize: (toTextView.font?.pointSize)!)
placeholderLabel.sizeToFit()
toTextView.addSubview(placeholderLabel)
placeholderLabel.frame.origin = CGPoint(x: 5, y: (toTextView.font?.pointSize)! / 2)
placeholderLabel.textColor = UIColor.lightGray
placeholderLabel.isHidden = !toTextView.text.isEmpty
}
// Use this function in the ViewController's textViewDidChange delegate method.
func textViewWithPlaceholderDidChange(_ textView: UITextView) {
placeholderLabel.isHidden = !textView.text.isEmpty
}
}
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。
无需添加任何第三方库。只需使用下面的代码…
class SubmitReviewVC : UIViewController, UITextViewDelegate {
@IBOutlet var txtMessage : UITextView!
var lblPlaceHolder : UILabel!
override func viewDidLoad() {
super.viewDidLoad()
txtMessage.delegate = self
lblPlaceHolder = UILabel()
lblPlaceHolder.text = "Enter message..."
lblPlaceHolder.font = UIFont.systemFont(ofSize: txtMessage.font!.pointSize)
lblPlaceHolder.sizeToFit()
txtMessage.addSubview(lblPlaceHolder)
lblPlaceHolder.frame.origin = CGPoint(x: 5, y: (txtMessage.font?.pointSize)! / 2)
lblPlaceHolder.textColor = UIColor.lightGray
lblPlaceHolder.isHidden = !txtMessage.text.isEmpty
}
func textViewDidChange(_ textView: UITextView) {
lblPlaceHolder.isHidden = !textView.text.isEmpty
}
}
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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