swift 实现一段文字 右下角最后一行提前开始省略

需要cocopods引入YYKit

pod "YYKit"

代码中实现这个类，主要是靠YYKit获取每行有什么文案，然后拆成两个UILabel实现。

import UIKit
import YYKit

//最后一行文案留一段距离提前开始省略的文案view.
//定宽 高度自适应，需要指定最大行数和最后一行要预留提前省略的距离
class RightBottomSpaceLabelView : UIView {
    
    private var label : UILabel = UILabel()
    private var label2 : UILabel = UILabel()//展示最后一行
    
    //调用后 本view的宽和高就定下来了.高度是最大行数或者文字行数，宽度为maxWidth
    //lastLineSpace 是最后一行到右边的留空距离，如果文字行数没有达到最大行，此属性无效
    func config(str:String,
                font:UIFont,
                textColor:UIColor,
                maxWidth: CGFloat,
                maxLines: Int,
                lastLineSpace:CGFloat) {
        
        label.numberOfLines = maxLines
        label.textColor = textColor
        label.font = font
        label.isHidden = false
        
        label2.numberOfLines = 1
        label2.textColor = textColor
        label2.font = font
        label2.isHidden = false
        
        let attributedString = NSMutableAttributedString(string: str)
        attributedString.addAttributes([.font: font], range: attributedString.rangeOfAll())
        let ranges = getLabelLinesRange(attributedText: attributedString, maxWidth: maxWidth)
        
        if ranges.count <= 1 {//只有一行
            label.isHidden = true
            label2.text = str
           
            label2.sizeToFit()
            if ranges.count < maxLines {
                label2.width = maxWidth
            }else{
                label2.width = maxWidth - lastLineSpace
            }
            self.size = CGSize(width: maxWidth, height: label2.height)
        }else{//超过一行
            if ranges.count < maxLines {//没有达到最大行数
                label2.isHidden = true
                label.text = str
               
                label.size = label.sizeThatFits(CGSize(width: maxWidth, height: CGFLOAT_MAX))
                self.size = label.size
            }else { //超过或者刚好等于最大行数
                
                let range = ranges[maxLines - 1]
                let lastIndex = range.location
                let firstStr = subString(str:str,fromIndex: 0, length: lastIndex)
                label.text = firstStr
               
                label.size = label.sizeThatFits(CGSize(width: maxWidth, height: CGFLOAT_MAX))
                label2.top = label.height
                let lastRange = ranges[maxLines - 1]
                label2.text = subString(str:str,fromIndex: lastRange.location, length: str.count - lastRange.location)
                
                label2.sizeToFit()
                label2.width = maxWidth - lastLineSpace
                self.size = CGSize(width: maxWidth, height: label2.bottom)
                
            }
        }
    }
    
  
    
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        
        addSubview(label)
        label.lineBreakMode = NSLineBreakMode.byTruncatingTail
        addSubview(label2)
        label2.lineBreakMode = NSLineBreakMode.byTruncatingTail
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    


    
    
    //获取每行文案的NSRange
    private func getLabelLinesRange(attributedText: NSMutableAttributedString, maxWidth: CGFloat) -> [NSRange] {
        var result: [NSRange] = []
        let container = YYTextContainer(size: CGSize(width: maxWidth, height: CGFLOAT_MAX))
        let layout = YYTextLayout(container: container, text: attributedText)
        let lines = layout?.lines
        for line in lines ?? [] {
            result.append(line.range)
        }
        return result
    }
    
    
    private func subString (str:String,fromIndex:Int , length:Int) -> String? {
        if(fromIndex >= str.count || fromIndex < 0 || length < 0){
            return nil
        }
        if((fromIndex + length) > str.count || (fromIndex + length) < 0){
            return nil
        }
        
        let startIndex = str.index(str.startIndex, offsetBy: fromIndex)
        let endIndex = str.index(startIndex, offsetBy: length)
        return String(str[startIndex..<endIndex])
    }
}

在viewcontroller中简单的使用示例：

import YYKit

class ViewController: UIViewController {
override func viewDidLoad() {
        super.viewDidLoad()

        let labelView = RightBottomSpaceLabelView()
        labelView.config(str: "发的客户表示卡号轧空给对方关电脑发生的放松放松",
                         font: UIFont.systemFont(ofSize: 16),
                         textColor: .black,
                         maxWidth: 100,
                         maxLines: 3,
                         lastLineSpace: 50)
        view.addSubview(labelView)
        labelView.top = 100
    }
}

示例效果：