iOS UITextView 屬性

有這樣一種需求，在UITextView的屬性里是沒(méi)有像UITextFiled一樣的占位文字的，那么要讓UITextView擁有占位文字，需要什么思路呢？

解決方案如下：

• 分析：如同UITextField一樣，當(dāng)沒(méi)有輸入時(shí)顯示占位文字，當(dāng)有輸入時(shí)隨即消失，當(dāng)輸入完再刪除時(shí)，又立刻出現(xiàn)
• 由上分析，可以肯定，這個(gè)占位文字我選擇一個(gè)UILable控件，因?yàn)樗軌蝻@示文字，而且便于修改占位文字屬性
• 通過(guò)分析，用通知或者代理來(lái)監(jiān)聽(tīng)UITextView屬性的改變，這里我使用通知！

具體代碼如下：

Swift代碼

import UIKit

/// 文本視圖
public class TCComposeTextView: UITextView {
    
    /// 占位標(biāo)簽
    fileprivate lazy var placeholderLabel = UILabel()
    
    override init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame, textContainer: textContainer)
        
        setupUI()
        setupInputAccessoryView()
    }
    
    required public init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    deinit {
        NotificationCenter.default.removeObserver(self)
    }
    
    // MARK: - 監(jiān)聽(tīng)方法
    @objc fileprivate func textChanged() {
        placeholderLabel.isHidden = self.hasText
    }
    
    @objc fileprivate func finishInput() {
        self.resignFirstResponder()
    }
}

fileprivate extension TCComposeTextView {
    
    func setupUI() {
        NotificationCenter.default.addObserver(self, selector: #selector(textChanged), name: .UITextViewTextDidChange, object: self)
        
        placeholderLabel.text = "寫下點(diǎn)什么吧..."
        placeholderLabel.font = self.font
        placeholderLabel.textColor = UIColor.lightGray
        placeholderLabel.frame.origin = CGPoint(x: 5, y: 8)
        placeholderLabel.sizeToFit()
        
        addSubview(placeholderLabel)
        
        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 TCComposeTextView: UITextViewDelegate {
    public func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
        if range.location > 99 {
            return false
        } else {
            return true
        }
    }
}

寫在最后

TCComposeTextView是繼承自UITextView的自定義子類，如果使用，直接創(chuàng)建復(fù)制粘貼即可。當(dāng)然有什么問(wèn)題，可以留言給我，O(∩_∩)O謝謝！