ios - BaseController 委托(delegate)在选项卡栏 Controller 内的所有继承 View Controller 中不起作用

Question

我很难理解为什么我在基本 Controller 中定义的委托(delegate)在继承的 View Controller 中不起作用。

我有一个 TabBarController，它有 2 个 ViewController。每个 ViewController 都是 BaseController 的子类。

BaseController 实现委托(delegate)并更新标签 View 。

当我启动应用程序并单击“播放”时，FirstVC 更新标签，但是当我将选项卡切换到 SecondVC 时，它开始更新，但是当我再次单击 FirstVC 时，更新卡住了并且不会更新标签，但标签一直在更新在 SecondVC 中。

import Foundation
import AVFoundation

protocol SharedPlayerNotificaions : class {

    func willPlay(status: Bool)
    func currentPlayTime(timeString: String)
}

class SharedPlayer : NSObject {

    static let sharedInstance = SharedPlayer()    
    private var player : AVPlayer?
    weak var delegate : SharedPlayerNotificaions?

    override private init() {
        super.init()
        player = AVPlayer()

    }

    override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
        if keyPath == "status" {

            if player?.status == AVPlayerStatus.Unknown {
                delegate?.willPlay(false)
            }
            if player?.status == AVPlayerStatus.Failed {
                print("failed")
                delegate?.willPlay(false)
            }

            if player?.status == AVPlayerStatus.ReadyToPlay {
                print("readytoplay")
                delegate?.willPlay(true)
            }
        }
        if keyPath == "rate" {
        }
        if keyPath == "duration" {   
        }
    }

    func play(){

        player?.play()
        let interval = CMTime(value: 1, timescale: 2)
        player?.addPeriodicTimeObserverForInterval(interval, queue: dispatch_get_main_queue(), usingBlock: { (progressTime) in
            let seconds = CMTimeGetSeconds(progressTime)
            let secondsString = String(format: "%02d", Int(seconds % 60))
            let minutesString = String(format: "%02d", Int(seconds / 60))
            self.delegate?.currentPlayTime("\(minutesString):\(secondsString)")
        })
    }

    func setUrl(urlString: String){

        if let url = NSURL(string: urlString){
            player = AVPlayer(URL: url)
            player?.addObserver(self, forKeyPath: "status", options: NSKeyValueObservingOptions.New, context: nil)
             player?.addObserver(self, forKeyPath: "rate", options: NSKeyValueObservingOptions.New, context: nil)
             player?.addObserver(self, forKeyPath: "duration", options: NSKeyValueObservingOptions.New, context: nil)
        }
    }
}

基础 Controller

    class BaseController : UIViewController, SharedPlayerNotificaions {

        let label = UILabel()

        override func viewDidLoad() {

            SharedPlayer.sharedInstance.delegate = self

            view.addSubview(label)
            label.translatesAutoresizingMaskIntoConstraints = false
            view.addConstraint(NSLayoutConstraint(item: label, attribute: .Left, relatedBy: .Equal, toItem: view, attribute: .Left, multiplier: 1, constant: 10))
            view.addConstraint(NSLayoutConstraint(item: label, attribute: .Width, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 1, constant: 50))
            view.addConstraint(NSLayoutConstraint(item: label, attribute: .Top, relatedBy: .Equal, toItem: view, attribute: .Top, multiplier: 1, constant: 10))

            label.text = "00:00"
        }


   func currentPlayTime(timeString: String) { 
    dispatch_async(dispatch_get_main_queue()) { 
        self.label.text = timeString
    }
}

        func willPlay(status: Bool) {

        }
}

第一 View Controller

class FirstViewController: BaseController {


    @IBAction func playButton(sender: AnyObject) {

        let urlString = "https://someStreamUrl"

        SharedPlayer.sharedInstance.setUrl(urlString)
        SharedPlayer.sharedInstance.play()

      }

}

第二 View Controller

class SecondViewController : BaseController {

    override func viewDidLoad() {

        super.viewDidLoad()
        view.backgroundColor = .redColor()
    } 
}

Answer 1

主要缺陷是 SharedPlayer 是单例。只有一个例子。它只能有一个代表。但是你创建了两个 View Controller 。两者都试图告诉单个共享 SharedPlayer 实例它是委托(delegate)。第二个获胜。

委托(delegate)模式只有在只有一个委托(delegate)的情况下才有效。在这种情况下，您有两个，因此您不能使用传统的委托(delegate)模式。

有几种可能的解决方案。

1. 更新 SharedPlayer 以接受委托(delegate)数组而不是单个委托(delegate)。
2. 使用NSNotificationCenter。让 SharedPlayer 发布通知并让每个 View Controller 注册每个可能的通知。