我想要具有与Android相同的占位符行为的自定义UITextfield，也想要UITextfield中的错误标签

Question

我想要自定义的F，它具有与android相同的占位符行为，我还想要UITextfield中的错误标签。

最近我在android中见过。它们具有默认的文本区域，在该区域中，用户开始书写时不会隐藏占位符，而不是隐藏它们，而是使占位符位于textarea的上方。

Answer 1

最近，我创建了CustomTextfield类，它与您的要求相同。

以下是Github链接，用于下载课程及其用法https://github.com/indrajitv/CustomTextField

下面是代码，

//
//  File.swift
//  customTextField
//
//  Created by indrajit on 17/08/18.
//  Copyright © 2018 indrajit. All rights reserved.
//
import UIKit
@IBDesignable
open class CustomTextField:UITextField{

   private var labelPlaceholderTitleTop:NSLayoutConstraint!
   private var labelPlaceholderTitleCenterY:NSLayoutConstraint!
   private var labelPlaceholderTitleLeft:NSLayoutConstraint!

    @IBInspectable var allowToShrinkPlaceholderSizeOnEditing = true
    @IBInspectable var shrinkSizeOfPlaceholder:CGFloat = 0

    @IBInspectable var placeHolderColor:UIColor = .lightGray{
        didSet{
            labelPlaceholderTitle.textColor = placeHolderColor
        }
    }
    open override var font: UIFont?{
        didSet{
            labelPlaceholderTitle.font = font
        }
    }
    @IBInspectable var heightOfBottomLine:CGFloat = 1{
        didSet{
            heightAnchorOfBottomLine.constant = heightOfBottomLine
        }
    }

    open override var leftView: UIView?{
        didSet{
            if let lv = leftView{
                labelPlaceholderTitleLeft.constant = lv.frame.width+leftPadding
            }
        }
    }

    @IBInspectable var leftPadding:CGFloat = 0{
        didSet{
            labelPlaceholderTitleLeft.constant = leftPadding
        }
    }


    @IBInspectable var errorText:String = ""{
        didSet{
            self.labelError.text = errorText
        }
    }
    @IBInspectable var errorColor:UIColor = .red{
        didSet{
            labelError.textColor = errorColor
        }
    }
    @IBInspectable var errorFont:UIFont = UIFont.systemFont(ofSize: 10){
        didSet{
            self.labelError.font = errorFont
        }
    }

    @IBInspectable var shakeIntensity:CGFloat = 5

   private var heightAnchorOfBottomLine:NSLayoutConstraint!

    lazy var labelPlaceholderTitle:UILabel={
        let label = UILabel()
        label.numberOfLines = 0
        label.translatesAutoresizingMaskIntoConstraints = false
        label.font = self.font
        label.adjustsFontSizeToFitWidth = true
        return label
    }()

    lazy var labelError:UILabel={
        let label = UILabel()
        label.numberOfLines = 0
        label.translatesAutoresizingMaskIntoConstraints = false
        label.adjustsFontSizeToFitWidth = true
        label.text = self.errorText
        label.textAlignment = .right
        label.font = self.errorFont
        label.textColor = errorColor
        return label
    }()

    let bottonLineView:UIView={
        let view = UIView()
        view.backgroundColor = .red
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()

    override init(frame: CGRect) {
        super.init(frame: frame)
        self.initalSetup()
    }
    required public init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        self.initalSetup()
    }

    override open func prepareForInterfaceBuilder() {
        self.initalSetup()
    }

    open override func awakeFromNib() {
        self.labelError.isHidden = true
    }

    func initalSetup(){

        self.labelPlaceholderTitle.text = placeholder
        placeholder = nil
        borderStyle = .none
        bottonLineView.removeFromSuperview()

        addSubview(bottonLineView)
        bottonLineView.leftAnchor.constraint(equalTo: leftAnchor, constant: 0).isActive = true
        bottonLineView.rightAnchor.constraint(equalTo: rightAnchor, constant: 0).isActive = true
        bottonLineView.bottomAnchor.constraint(equalTo: bottomAnchor, constant: 0).isActive = true

        heightAnchorOfBottomLine = bottonLineView.heightAnchor.constraint(equalToConstant: heightOfBottomLine)
        heightAnchorOfBottomLine.isActive = true

        addSubview(labelPlaceholderTitle)
        labelPlaceholderTitleLeft = labelPlaceholderTitle.leftAnchor.constraint(equalTo: leftAnchor, constant: leftPadding)
        labelPlaceholderTitleLeft.isActive = true
        labelPlaceholderTitle.rightAnchor.constraint(equalTo: rightAnchor, constant: 0).isActive = true
        labelPlaceholderTitleTop = labelPlaceholderTitle.topAnchor.constraint(equalTo: topAnchor, constant: 0)
        labelPlaceholderTitleTop.isActive = false

        labelPlaceholderTitleCenterY = labelPlaceholderTitle.centerYAnchor.constraint(equalTo: centerYAnchor, constant: 0)
        labelPlaceholderTitleCenterY.isActive = true


        addSubview(labelError)
        labelError.leftAnchor.constraint(equalTo: leftAnchor, constant: 0).isActive = true
        labelError.rightAnchor.constraint(equalTo: rightAnchor, constant: 0).isActive = true
        labelError.topAnchor.constraint(equalTo: bottonLineView.bottomAnchor, constant: 2).isActive = true


        addTarget(self, action: #selector(self.textFieldDidChange), for: .editingChanged)


    }


    @objc func textFieldDidChange(){

        func animateLabel(){
            UIView.animate(withDuration: 0.2, delay: 0, usingSpringWithDamping: 1, initialSpringVelocity: 1, options: .curveEaseOut, animations: {
                self.layoutIfNeeded()
            }, completion: nil)
        }

        if let enteredText = text,enteredText != ""{
            if labelPlaceholderTitleCenterY.isActive{
                labelPlaceholderTitleCenterY.isActive = false
                labelPlaceholderTitleTop.isActive = true
                labelPlaceholderTitleTop.constant = -5
                if allowToShrinkPlaceholderSizeOnEditing{
                    let currentFont = font == nil ? UIFont.systemFont(ofSize: 16) : font!
                    let shrinkSize = shrinkSizeOfPlaceholder == 0 ? currentFont.pointSize-3 : shrinkSizeOfPlaceholder
                    labelPlaceholderTitle.font = UIFont.init(descriptor: currentFont.fontDescriptor, size:shrinkSize)
                }
                animateLabel()
            }
        }else{
            labelPlaceholderTitleCenterY.isActive = true
            labelPlaceholderTitleTop.isActive = false
            labelPlaceholderTitleTop.constant = 0
            labelPlaceholderTitle.font = font
            animateLabel()
        }
    }



    @objc public func showError(){
        self.labelError.isHidden = false
        let animation = CABasicAnimation(keyPath: "position")
        animation.duration = 0.07
        animation.repeatCount = 4
        animation.autoreverses = true
        animation.fromValue = NSValue(cgPoint: CGPoint(x: center.x - shakeIntensity, y: center.y))
        animation.toValue = NSValue(cgPoint: CGPoint(x: center.x + shakeIntensity, y: center.y))
        layer.add(animation, forKey: "position")
    }

    @objc public func hideError(){
        self.labelError.isHidden = true
    }

} 

**用法：

//
//  ViewController.swift
//  customTextField
//
//  Created by indrajit on 16/08/18.
//  Copyright © 2018 indrajit. All rights reserved.
//
import UIKit

class ViewController: UIViewController {
    @IBOutlet weak var text: CustomTextField!

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }



    @IBAction func okClicked(_ sender: UIButton) {

        if text.text! == ""{
                text.showError()
        }else{
            text.hideError()
        }

    }

}

输出：