UITableView进阶

1.2.1UITableViewCell点击内容扩展效果（如下图所示）

 

1.2.2实现原理

点击之后单元格Label的linesofnumber变量改变，重新加载即看到不同数量的lines

 

1.2.3源码

import UIKit

class ViewController: UIViewController,UITableViewDelegate,UITableViewDataSource {
    
    
    var cellText = "hello world\nhello world\nhello world\nhello world\nhello world\nhello world\nhello world\n"
    
    @IBOutlet weak var tableView: UITableView!

　　//这是一个字典变量，用来存放label的lines值
    var dict:Dictionary<String,String> = [:]
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        
        
        tableView.estimatedRowHeight = 60
        
        tableView.rowHeight = UITableViewAutomaticDimension
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    
    func numberOfSectionsInTableView(tableView: UITableView) -> Int {
        return 1
    }
    
    func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 100
    }
    
    func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCellWithIdentifier("Cell",forIndexPath: indexPath)
        let label = cell.contentView.viewWithTag(100) as! UILabel
        label.text = cellText
        if dict[String(indexPath.row)] == "0"{
            label.numberOfLines = 0
        }else{
            label.numberOfLines = 1
        }
        
        return cell
    }
    
    func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
        let cell = tableView.cellForRowAtIndexPath(indexPath)
        let label = cell?.contentView.viewWithTag(100) as! UILabel

　　　　　//beginUpdates()和endUpdattes()之前的代码会形式一个帧播放效果，就像实现动画一样
        tableView.beginUpdates()
        if label.numberOfLines == 0{
            label.numberOfLines = 1
            dict[String(indexPath.row)] = "1"
        }else{
            label.numberOfLines = 0
            dict[String(indexPath.row)] = "0"
        }
        tableView.endUpdates()
    }
}