Swift iOS ： 根据内容调整Cell高度的方法

有时候，需要动态调整UITableView的Cell高度，比如内部有一个TextView，内容由用户决定，可长可短的情况下，肯定是希望Cell和TextView可以展示全部内容，因此也需要Cell高度也跟着同步越高了。

如下代码，展示一个长度变化的TextView，当内容变化时，Cell高度会跟着变化。当通过UITableView.reloadData加载数据时，会触发高度计算函数：

func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat

代码如下：

import UIKit
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        self.window = UIWindow(frame: UIScreen.main.bounds)
        let page = Page()
        page.view.backgroundColor = .blue
        self.window!.rootViewController = page
        self.window?.makeKeyAndVisible()
        return true
    }
}
class Table : UITableView,UITableViewDataSource,UITableViewDelegate{
    let oldstr = "swift"
    let newstr = "The powerful programming language that is also easy to learn. Swift is a powerful and intuitive programming language for macOS, iOS, watchOS and tvOS."
    var arr = [""]
    var textView : UITextView = UITextView()
    override init(frame: CGRect, style: UITableViewStyle) {
        super.init(frame:frame,style:style)
        arr = [oldstr]
        self.dataSource = self
        self.delegate = self
    }
    required init?(coder aDecoder: NSCoder) {
        super.init(coder:aDecoder)
    }
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return arr.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let a = UITableViewCell(style: .default, reuseIdentifier: nil)
        textView.frame = a.contentView.frame
        textView.text = arr[indexPath.row]
        a.contentView.addSubview(textView)
        return a
    }
    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat{

        textView.frame.size.height = textHeight()
        return textView.frame.height
    }
    func textHeight()-> CGFloat{
        let size = textView.sizeThatFits(CGSize(width: textView.frame.size.width, height: CGFloat.greatestFiniteMagnitude))
        return size.height
    }
}
class Page: UIViewController {
    var a : Table!
    override func viewDidLoad() {
        super.viewDidLoad()
        a  = Table()
        a.frame = CGRect(x: 0,y: 100,width: 300,height: 100)
        self.view.addSubview(a)
        let btn = UIButton()
        btn.frame = CGRect(x: 0,y: 200,width: 100,height: 20)
        btn.setTitle("BigString", for: .normal)
        btn.addTarget(self, action: #selector(tap), for: .touchDown)
        self.view.addSubview(btn)
    }
    func tap(){
        if a.arr == [a.newstr]{
            a.arr = [a.oldstr]
        }else{
            a.arr = [a.newstr]
        }
        a.reloadData()
    }
}

还有一种比较超脱的方式，就是监视textView.contentSize的变化，然后通知TableView重新装入数据，从而引发高度的重新计算。代码如下：

import UIKit
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        self.window = UIWindow(frame: UIScreen.main.bounds)
        let page = Page()
        page.view.backgroundColor = .blue
        self.window!.rootViewController = page
        self.window?.makeKeyAndVisible()
        return true
    }
}
class Table : UITableView,UITableViewDataSource,UITableViewDelegate{
    let oldstr = "swift"
    let newstr = "The powerful programming language that is also easy to learn. Swift is a powerful and intuitive programming language for macOS, iOS, watchOS and tvOS."
    var arr = [""]
    var textView : UITextView = UITextView()
    override init(frame: CGRect, style: UITableViewStyle) {
        super.init(frame:frame,style:style)
        arr = [oldstr]
        self.dataSource = self
        self.delegate = self
        self.kvoController.observe(self.textView, keyPath: "contentSize", options: [.new]) {
            [weak self] (observe, observer, change) -> Void in
                self!.reloadData()
        }
    }
    required init?(coder aDecoder: NSCoder) {
        super.init(coder:aDecoder)
    }
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return arr.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let a = UITableViewCell(style: .default, reuseIdentifier: nil)
        textView.frame = a.contentView.frame
        textView.text = arr[indexPath.row]
        a.contentView.addSubview(textView)
        return a
    }
    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat{
        textView.frame.size.height = textHeight()
        return textView.frame.height
    }
    func textHeight()-> CGFloat{
        let size = textView.sizeThatFits(CGSize(width: textView.frame.size.width, height: CGFloat.greatestFiniteMagnitude))
        return size.height
    }
}
class Page: UIViewController {
    var a : Table!
    override func viewDidLoad() {
        super.viewDidLoad()
        a  = Table()
        a.frame = CGRect(x: 0,y: 100,width: 300,height: 100)
        self.view.addSubview(a)
        let btn = UIButton()
        btn.frame = CGRect(x: 0,y: 200,width: 100,height: 20)
        btn.setTitle("BigString", for: .normal)
        btn.addTarget(self, action: #selector(tap), for: .touchDown)
        self.view.addSubview(btn)
    }
    func tap(){
        if a.arr == [a.newstr]{
            a.arr = [a.oldstr]
        }else{
            a.arr = [a.newstr]
        }
        a.textView.text = a.arr[0]
    }
}

这里使用了一个组件，是facebook开源的KVOController。因此需要使用Pod加入依赖并安装它。