Swift UITextView 扩展 Placeholder
import UIKit
fileprivate var kTextViewPlaceholderLabel : Int = 0x2019_00
fileprivate var kTextViewPlaceholder : Int = 0x2019_01
fileprivate var kTextViewPlaceholderColor : Int = 0x2019_02
fileprivate var kTextViewPlaceholderFont : Int = 0x2019_03
fileprivate var kTextViewPlaceholderKeys : Int = 0x2019_04
extension UITextView {
/// 占位符
var x_placeholder: String {
get {
if let placeholder = objc_getAssociatedObject(self, &kTextViewPlaceholder) as? String {
return placeholder
} else {
return ""
}
}
set {
objc_setAssociatedObject(self, &kTextViewPlaceholder, newValue, .OBJC_ASSOCIATION_RETAIN)
x_placeholderLabel.text = newValue
}
}
/// 占位符颜色
var x_placeholderColor: UIColor {
get {
if let placeholderColor = objc_getAssociatedObject(self, &kTextViewPlaceholderColor) as? UIColor {
return placeholderColor
} else {
return UIColor.subTitleColor
}
}
set {
objc_setAssociatedObject(self, &kTextViewPlaceholderColor, newValue, .OBJC_ASSOCIATION_RETAIN)
x_placeholderLabel.textColor = newValue
}
}
/// 占位符字体
var x_placeholderFont: UIFont {
get {
if let placeholderFont = objc_getAssociatedObject(self, &kTextViewPlaceholderColor) as? UIFont {
return placeholderFont
} else {
return UIFont.systemFont(ofSize: 12)
}
}
set {
objc_setAssociatedObject(self, &kTextViewPlaceholderColor, newValue, .OBJC_ASSOCIATION_RETAIN)
x_placeholderLabel.font = newValue
}
}
/// 占位符 标签
@IBInspectable var x_placeholderLabel: UILabel {
get {
var _placeholderLabel = UILabel(font: self.font ?? UIFont.systemFont(ofSize: 12), color: .subTitleColor, alignment: .left)
if let label = objc_getAssociatedObject(self, &kTextViewPlaceholderLabel) as? UILabel {
_placeholderLabel = label
} else {
objc_setAssociatedObject(self, &kTextViewPlaceholderLabel, _placeholderLabel, .OBJC_ASSOCIATION_RETAIN)
}
addPlaceholderLabelToSuperView(label: _placeholderLabel)
return _placeholderLabel
}
set {
objc_setAssociatedObject(self, &kTextViewPlaceholderLabel, newValue, .OBJC_ASSOCIATION_RETAIN)
addPlaceholderLabelToSuperView(label: newValue)
}
}
/// 是否需要添加占位符到父视图
fileprivate var x_placeHolderNeedAddToSuperView: Bool {
get {
if let isAdded = objc_getAssociatedObject(self, &kTextViewPlaceholderKeys) as? Bool {
return isAdded
}
return true
}
set {
objc_setAssociatedObject(self, &kTextViewPlaceholderKeys, newValue, .OBJC_ASSOCIATION_RETAIN)
}
}
/// 添加占位符到父视图
///
/// - Parameter label: 占位符 标签
fileprivate func addPlaceholderLabelToSuperView(label: UILabel) {
guard x_placeHolderNeedAddToSuperView else { return }
x_placeHolderNeedAddToSuperView = false
NotificationCenter.default.addObserver(self, selector: #selector(x_textChange(noti:)), name: UITextView.textDidChangeNotification, object: nil)
addSubview(label)
label.snp.makeConstraints { (make) in
make.edges.equalToSuperview().inset(UIEdgeInsets(top: 7, left: 2, bottom: 0, right: 0))
}
}
/// 编辑事件
@objc fileprivate func x_textChange(noti: NSNotification) {
let isEmpty = text.isEmpty
print("text:\(String(describing: text))\nisEmpty:\(isEmpty)")
x_placeholderLabel.text = isEmpty ? x_placeholder : ""
x_placeholderLabel.isHidden = !isEmpty
}
}
