自定义带占位符的LFTextView

有点潦草简单贴一下，主要是继承UITextView，重写init方法添加placeholderLabel然后根据监听的文字控制显隐

//
//  LFTextView.swift
//
//  Created by 刘刘峰 on 2019/11/25.
//  Copyright © 2019 刘刘峰. All rights reserved.
//

import UIKit

@objc protocol LFTextViewDelegate {
    @objc optional func textDidChange(text:String?)->Void
}
class LFTextView: UITextView {
    
    weak var textDelegate:LFTextViewDelegate?
    ///占位标签
    public lazy var placeholderLabel = UILabel()
    ///定义最大高度
    var maxHeight:CGFloat =  100
    
    //设置占位符y坐标 默认0
    var placeHolderMarginY:CGFloat? {
        didSet {
            placeholderLabel.snp_remakeConstraints{ (make) in
                make.left.equalToSuperview().offset(10)
                make.right.equalToSuperview().offset(-10)
                make.height.equalTo(20)
                make.top.equalToSuperview().offset(self.placeHolderMarginY!)
            }

        }
    }

    var maxLength:Int = 60
    var currentLength:Int = 0

    lazy var lengthLab:UILabel = {
        var label = UILabel()
        label.font = FONT(font: 12)
        label.textAlignment = .right
        label.textColor = AppColor.darkgGray
        return label
    }()
    
    
    
    var showLength:Bool = true
    
    override init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame,textContainer:textContainer)
        setupUI()
        setupInputAccessoryView()

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

    }
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    deinit {
        NotificationCenter.default.removeObserver(self)
    }
    
    // MARK: - 监听text改变方法
    @objc fileprivate func textChanged(noti:Notification) {
        placeholderLabel.isHidden = self.hasText
        DLog(noti.object)
        let textView = noti.object as? LFTextView
        
        if self.textDelegate != nil {
            self.textDelegate?.textDidChange?(text:textView?.text)
        }
    }

    @objc fileprivate func finishInput() {
        self.resignFirstResponder()
    }
    
}

fileprivate extension LFTextView {
    func setupUI() {
                
        NotificationCenter.default.addObserver(self, selector: #selector(textChanged(noti:)), name:UITextView.textDidChangeNotification, object: self)
                
        let contentView = UIView()
        addSubview(contentView)
        //否则会拦截输入手势
        contentView.isUserInteractionEnabled = false
        contentView.snp_makeConstraints { (make) in
            make.edges.equalToSuperview()
            make.width.equalToSuperview()
            make.height.equalToSuperview()
        }
        
        placeholderLabel.font = self.font
        placeholderLabel.textColor = AppColor.lightGray
        
        contentView.addSubview(placeholderLabel)

        placeholderLabel.snp_makeConstraints { (make) in
            make.left.equalToSuperview().offset(10)
            make.right.equalToSuperview().offset(-10)
            make.height.equalTo(20)
            make.centerY.equalToSuperview()

        }
        
        delegate = self
        
    }
    
    func setupInputAccessoryView() {
        let toolbar = UIToolbar(frame: CGRect(x: 0, y: 0, width: UIScreen.main.bounds.width, height: 44.0))
        let doneItem = UIBarButtonItem(title: "完成", style: .done, target: self, action: #selector(finishInput))
        let flexibleItem = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)
        toolbar.items = [flexibleItem, doneItem]
        
        self.inputAccessoryView = toolbar
    }
    
}

// MARK: - UITextViewDelegate
extension LFTextView: UITextViewDelegate {
    public func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
        if range.location > maxLength-1 {
            return false
        } else {
            return true
        }
    }
    
    func textViewDidChange(_ textView: UITextView) {
        //获取frame的值
        let frame = textView.frame
        //定义一个constrainSize值用于计算textview的高度
        
        let constrainSize = CGSize(width:frame.size.width,height:CGFloat(MAXFLOAT))
         
        //获取textview的真实高度
        
        var size = textView.sizeThatFits(constrainSize)
        
        //如果textview的高度大于最大高度高度就为最大高度并可以滚动，否则不能滚动
        
        if size.height >= maxHeight{

            size.height = maxHeight

            textView.isScrollEnabled = true

        }else{

            textView.isScrollEnabled = false

        }

        //重新设置textview的高度
        
        textView.frame.size.height = size.height
        
        currentLength = textView.text.length
        
        self.lengthLab.text = "\(currentLength)/\(maxLength)"
        
        
    }
}