在 AVPlayer 上添加 ActivityIndicator 并移除 addObserver答案

【问题标题】：Add ActivityIndicator and remove addObserver on AVPlayer在 AVPlayer 上添加 ActivityIndicator 并移除 addObserver
【发布时间】：2016-07-24 17:06:12
【问题描述】：

我试图在播放器（缓冲或加载）时显示ActivityIndicator，当它开始播放时它停止ActivityIndicator。此外，当我停止播放器时，它（removeObserver 或 deallocObservers）是 AVPlayer。当我播放音乐时，它会显示 ActivityIndicator 直到它准备好播放，但它会在播放前 4.5 秒停止为 ActivityIndicator 设置动画。问题是当我停止 AVPlayer 或点击另一个播放按钮时，它会在删除 AVPlayer 观察者时给我错误。谁能告诉我代码中的错误在哪里以及如何修复它，谢谢。

var selectIndex:Int = -1

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell{
        let cell = collectionView.dequeueReusableCellWithReuseIdentifier(reuseIdentifier, forIndexPath: indexPath) as! RadioCollectionViewCell
        cell.backgroundColor = UIColor.yellowColor()

        let object = objects[indexPath.row]
        cell.img.image = UIImage(named: object["image"]!)
        cell.btnPlay.addTarget(self, action: Selector("audioControlButtonAction:"), forControlEvents: UIControlEvents.TouchUpInside)
        cell.btnPlay.tag = indexPath.row+1


        return cell
    }

func audioControlButtonAction(sender: UIButton){

        if player != nil && player?.currentItem != nil {
            deallocObservers(player!)
        }

        var btn:NSInteger
        btn = sender.tag as NSInteger

        let object = objects[btn-1]
        let nurl = NSURL(string: "\(object["url"]!)")!
        playerItem = AVPlayerItem(URL: nurl)
        player=AVPlayer(playerItem: playerItem!)

        print(selectIndex)
        if selectIndex != -1 && selectIndex != sender.tag
        {
            let bt:UIButton = self.view.viewWithTag(selectIndex) as! UIButton

            if bt.selected == true
            {
                bt.selected = false
                deallocObservers(player!)
            }
        }

        if sender.selected == false
        {
            player!.addObserver(self, forKeyPath: "status", options:NSKeyValueObservingOptions(), context: nil)
            player!.addObserver(self, forKeyPath: "playbackBufferEmpty", options:NSKeyValueObservingOptions(), context: nil)
            // player!.addObserver(self, forKeyPath: "playbackLikelyToKeepUp", options:NSKeyValueObservingOptions(), context: nil)
            player!.addObserver(self, forKeyPath: "loadedTimeRanges", options: NSKeyValueObservingOptions(), context: nil)

            player!.play()
            sender.selected = true
            selectIndex = sender.tag
            activityView.startAnimating()
            // self.view.userInteractionEnabled = false


        }
        else
        {

            deallocObservers(player!)
            player?.pause()
            sender.selected = false
            selectIndex = -1
        }

        print(selectIndex)

    }

    func deallocObservers(player: AVPlayer) {

        player.removeObserver(self, forKeyPath: "status")
        player.removeObserver(self, forKeyPath: "playbackBufferEmpty")
        // player.removeObserver(self, forKeyPath: "playbackLikelyToKeepUp")
        player.removeObserver(self, forKeyPath: "loadedTimeRanges")
    }


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

        if object?.isEqual(player) == true && keyPath == "status" {
            print("status")

            if player?.status == AVPlayerStatus.ReadyToPlay{
                print("AVPlayerStatus.ReadyToPlay")
                activityView.stopAnimating()
                // self.view.userInteractionEnabled = true
            }else{
                print("AVPlayerStatus.NotReadyToPlay")
                activityView.startAnimating()
//                self.view.userInteractionEnabled = false
            }

          //if keyPath == "playbackLikelyToKeepUp" {
               //activityView.stopAnimating()
               ////self.view.userInteractionEnabled = true
               //print("playbackLikelyToKeepUp")
            //}
            if keyPath == "playbackBufferEmpty" {
                activityView.startAnimating()
                self.view.userInteractionEnabled = false

                let createAccountErrorAlert: UIAlertView = UIAlertView()
                createAccountErrorAlert.delegate = self
                createAccountErrorAlert.title = "No Internet Connection"
                createAccountErrorAlert.message = "Make sure your device is connected to the internet."
                createAccountErrorAlert.addButtonWithTitle("Dismiss")

                createAccountErrorAlert.show()

                print("playbackBufferEmpty")
            }

            if player?.status == AVPlayerStatus.Failed{
                print("Something went wrong . player.error should contain some information")
            }
        }
    }

输出

-1
1
status
AVPlayerStatus.ReadyToPlay
1
2016-07-24 21:51:00.585 Radio[777:23560] *** Terminating app due to uncaught exception 'NSRangeException', reason: 'Cannot remove an observer <Radio.RadioCollectionViewController 0x7fbe39d47f70> for the key path "status" from <AVPlayer 0x7fbe39e67410> because it is not registered as an observer.'
*** First throw call stack:
(
    0   CoreFoundation                      0x00000001019b2e65 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x0000000103b51deb objc_exception_throw + 48
    2   CoreFoundation                      0x00000001019b2d9d +[NSException raise:format:] + 205
    3   Foundation                          0x0000000101fc4d51 -[NSObject(NSKeyValueObserverRegistration) _removeObserver:forProperty:] + 504
    4   Foundation                          0x0000000101fc4abd -[NSObject(NSKeyValueObserverRegistration) removeObserver:forKeyPath:] + 84
    5   Radio                               0x00000001014a935d _TFC5Radio29RadioCollectionViewController16deallocObserversfS0_FCSo8AVPlayerT_ + 141
    6   Radio                               0x00000001014a8fbe _TFC5Radio29RadioCollectionViewController24audioControlButtonActionfS0_FCSo8UIButtonT_ + 5326
    7   Radio                               0x00000001014a92ba _TToFC5Radio29RadioCollectionViewController24audioControlButtonActionfS0_FCSo8UIButtonT_ + 58
    8   UIKit                               0x0000000102630194 -[UIApplication sendAction:to:from:forEvent:] + 92
    9   UIKit                               0x000000010279f6fc -[UIControl sendAction:to:forEvent:] + 67
    10  UIKit                               0x000000010279f9c8 -[UIControl _sendActionsForEvents:withEvent:] + 311
    11  UIKit                               0x000000010279eaf8 -[UIControl touchesEnded:withEvent:] + 601
    12  UIKit                               0x000000010269f49b -[UIWindow _sendTouchesForEvent:] + 835
    13  UIKit                               0x00000001026a01d0 -[UIWindow sendEvent:] + 865
    14  UIKit                               0x000000010264eb66 -[UIApplication sendEvent:] + 263
    15  UIKit                               0x0000000102628d97 _UIApplicationHandleEventQueue + 6844
    16  CoreFoundation                      0x00000001018dea31 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
    17  CoreFoundation                      0x00000001018d495c __CFRunLoopDoSources0 + 556
    18  CoreFoundation                      0x00000001018d3e13 __CFRunLoopRun + 867
    19  CoreFoundation                      0x00000001018d3828 CFRunLoopRunSpecific + 488
    20  GraphicsServices                    0x0000000106247ad2 GSEventRunModal + 161
    21  UIKit                               0x000000010262e610 UIApplicationMain + 171
    22  Radio                               0x00000001014afd5d main + 109
    23  libdyld.dylib                       0x000000010468892d start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

我找到了从该链接中删除status observer 的解决方案，但不知道如何快速转换它。

解决方案

@try { [player removeObserver:self forKeyPath:@"status"]; } @catch (NSException *exception) { } @finally { } –

【问题讨论】：

标签： ios objective-c swift swift2 avplayer

【解决方案1】：

快速版本

目标 C

@try { [player removeObserver:self forKeyPath:@"status"]; } @catch (NSException *exception) { } @finally { }

斯威夫特

Error Handling in Swift2

do {
          try player.removeObserver(self, forKeyPath: "status")
        }

  catch {
    print("error")
  }
    defer{
      print("finally statement here")
    }

【讨论】：

感谢 Chandan Prajapati。现在我已经看到这个问题是由于我再次播放音乐时再次调用deallocObservers(player!) 造成的。因为当我再次播放音乐时。它进入if player != nil && player?.currentItem != nil { deallocObservers(player!) }

【解决方案2】：

问题是“deallocObservers”方法被调用了两次，而这两次调用之间没有添加任何观察者。我想曾经在这里：

    if player != nil && player?.currentItem != nil {
        deallocObservers(player!)
    }

第二次调用此方法时，播放器变量和当前项目不会为空。第二次调用 deallocObservers 可能在这里：

        if bt.selected == true
        {
            bt.selected = false
            deallocObservers(player!)
        }

我会在 deallocObservers 方法中放置一个断点，以查看该方法被调用了多少次以及谁调用了它（查看堆栈跟踪）。

【讨论】：

现在我从if bt.selected == true 和暂停方法中删除“deallocObservers”。我已经看到使用断点，当我暂停它时删除观察者，但是当我再次播放它时，它再次继续if player != nil && player?.currentItem != nil 方法，所以观察者已经被删除，因此由于这个原因它给了我同样的错误。你知道我需要添加什么条件吗？谢谢
我会从 if bt.selected == true 中删除 deallocObservers(player!) 调用。真的需要吗？

【解决方案3】：

我添加了对这些条件的检查。

var check = true
func audioControlButtonAction(sender: UIButton){

        if check == false {
            deallocObservers(player!)
        }
        if sender.selected == false{
            check = false
        }
        else{
            check = true
        }        
    }

【讨论】：