Uitableview 类AVPlayerItem已解除分配，而键值观察员仍在注册

我得到了以下错误，但奇怪的是，只有当我使用分页在tableview上滚动，加载第二组帖子，然后尝试移动到新的view控制器时，才会发生这种情况， 如果我只加载文章的第一页，并移到另一个视图控制器，则不会发生崩溃：

Terminating app due to uncaught exception 'NSInternalInconsistencyException', 
reason: 'An instance 0x170212330 of class AVPlayerItem was deallocated while key 
value observers were still registered with it. 
Current observation info: <NSKeyValueObservationInfo 0x174820360> (
<NSKeyValueObservance 0x174244290: Observer: 0x101c76c00, Key path: 
playbackBufferEmpty, Options: <New: YES, Old: NO, Prior: NO> Context: 0x0, 
Property: 0x174243ea0>
<NSKeyValueObservance 0x1754583c0: Observer: 0x101c76c00, Key path: 
playbackLikelyToKeepUp, Options: <New: YES, Old: NO, Prior: NO> Context: 0x0, 
Property: 0x174243f60>

我从添加第二页中看到的唯一区别是：

执行常规表格视图加载时，我执行以下操作：

  [_tableView reloadData];

在同一表视图上加载第二页时，我会：

 [_tableView beginUpdates];
 [_tableView insertRowsAtIndexPaths:[[GlobalSingleton sharedInstance] indexPathsToInsert]  withRowAnimation:UITableViewRowAnimationTop];
 [_tableView endUpdates];

在我的手机上，我会：

- (void)prepareForReuse{
    [self removePlayer];

}

- (void) dealloc {
[self removePlayer];
}

-(void)removePlayer{
    @try{

    [self.videoItem removeObserver:self forKeyPath:@"playbackBufferEmpty"];
    [self.videoItem removeObserver:self forKeyPath:@"playbackLikelyToKeepUp"];




    [[NSNotificationCenter defaultCenter] removeObserver:self name:AVPlayerItemPlaybackStalledNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:AVPlayerItemDidPlayToEndTimeNotification object:nil];

        NSLog(@"remove Observer!");
    // [avLayer.player pause];
    }
    @catch (NSException * e) {
        NSLog(@"Exception: %@", e);
    }
    @finally {
        NSLog(@"finally");
        [self.avLayer removeFromSuperlayer];
        self.playIV.hidden = YES;
        self.videoActivity.hidden = YES;
        self.videoView.hidden = YES;
        self.videoItem = nil;
        self.avLayer = nil;
        self.videoPlayer = nil;
    }

}

---

insertRowsAtIndexPaths是否可能导致细胞永远无法释放？我找不到如何注册观察者。

在使用insertRowsAtIndexPaths时，prepareForReuse没有被调用，因此我解决了这个问题，在向单元格添加新的视频项之前，先在CellForRowsatindexPath上注销观察者：

- (UITableViewCell *)tableView:(UITableView *)tableViewSelected cellForRowAtIndexPath:(NSIndexPath *)indexPath {
NSString *identifier = @"postCell";
PostCell* updateCell = [tableViewSelected dequeueReusableCellWithIdentifier:identifier];

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);

    dispatch_async(queue, ^{

        dispatch_sync(dispatch_get_main_queue(), ^{
            NSString* videoString = [NSString stringWithFormat:@"%@%@%@",UrlBase,PostVideos,post.video];
            NSString* expandedPath = [videoString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
             NSURL *videoURL = [NSURL URLWithString:expandedPath];

            /** SOLUTION STARTS HERE **/
            @try{
                  [self.videoItem removeObserver:self forKeyPath:@"playbackBufferEmpty"];
                  [self.videoItem removeObserver:self forKeyPath:@"playbackLikelyToKeepUp"];
                  [[NSNotificationCenter defaultCenter] removeObserver:self name:AVPlayerItemPlaybackStalledNotification object:nil];
                  [[NSNotificationCenter defaultCenter] removeObserver:self name:AVPlayerItemDidPlayToEndTimeNotification object:nil];

           }
           @catch (NSException * e) {
               NSLog(@"Exception: %@", e);
           }
           @finally {
               NSLog(@"finally");
           }
           /** SOLUTION ENDS HERE **/

            updateCell.videoItem  = [AVPlayerItem playerItemWithURL:videoURL];
            [updateCell.videoItem addObserver:updateCell forKeyPath:@"playbackBufferEmpty" options:NSKeyValueObservingOptionNew context:nil];
            [updateCell.videoItem addObserver:updateCell forKeyPath:@"playbackLikelyToKeepUp" options:NSKeyValueObservingOptionNew context:nil];

            updateCell.videoPlayer = [AVPlayer playerWithPlayerItem:updateCell.videoItem];
            updateCell.avLayer = [AVPlayerLayer playerLayerWithPlayer:updateCell.videoPlayer];
            updateCell.videoPlayer.actionAtItemEnd = AVPlayerActionAtItemEndNone;

            [[NSNotificationCenter defaultCenter] addObserver:updateCell selector:@selector(itemDidBufferPlaying:) name:AVPlayerItemPlaybackStalledNotification object:nil];
            [[NSNotificationCenter defaultCenter] addObserver:updateCell selector:@selector(itemDidFinishPlaying:) name:AVPlayerItemDidPlayToEndTimeNotification object:[updateCell.videoPlayer currentItem]];


            updateCell.avLayer.frame = updateCell.picture.bounds;
            [updateCell.videoView.layer addSublayer:updateCell.avLayer];

            [updateCell.avLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
            if(indexPath.row==0){
                [updateCell.videoPlayer play];
            }
        });
    });
    return updateCell;

}

---

我的解决方案是删除前两个观察者：[updateCell.videoItem addObserver:updateCell forKeyPath:@“Playbackufferempty”选项：NSKeyValueObservingOptionNew context:nil]；[updateCell.videoItem addObserver:updateCell forKeyPath:@“playbackLikelyToKeepUp”选项：NSKeyValueObservingOptionNew context:nil]；此外，我还发现prepareForReuse似乎不能很好地处理InsertRowsatindExpath，但如果在创建新的videoItem之前删除CellForRowatineXpath上的观察者，它也可以工作。

- (UITableViewCell *)tableView:(UITableView *)tableViewSelected cellForRowAtIndexPath:(NSIndexPath *)indexPath {
NSString *identifier = @"postCell";
PostCell* updateCell = [tableViewSelected dequeueReusableCellWithIdentifier:identifier];

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);

    dispatch_async(queue, ^{

        dispatch_sync(dispatch_get_main_queue(), ^{
            NSString* videoString = [NSString stringWithFormat:@"%@%@%@",UrlBase,PostVideos,post.video];
            NSString* expandedPath = [videoString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
             NSURL *videoURL = [NSURL URLWithString:expandedPath];

            /** SOLUTION STARTS HERE **/
            @try{
                  [self.videoItem removeObserver:self forKeyPath:@"playbackBufferEmpty"];
                  [self.videoItem removeObserver:self forKeyPath:@"playbackLikelyToKeepUp"];
                  [[NSNotificationCenter defaultCenter] removeObserver:self name:AVPlayerItemPlaybackStalledNotification object:nil];
                  [[NSNotificationCenter defaultCenter] removeObserver:self name:AVPlayerItemDidPlayToEndTimeNotification object:nil];

           }
           @catch (NSException * e) {
               NSLog(@"Exception: %@", e);
           }
           @finally {
               NSLog(@"finally");
           }
           /** SOLUTION ENDS HERE **/

            updateCell.videoItem  = [AVPlayerItem playerItemWithURL:videoURL];
            [updateCell.videoItem addObserver:updateCell forKeyPath:@"playbackBufferEmpty" options:NSKeyValueObservingOptionNew context:nil];
            [updateCell.videoItem addObserver:updateCell forKeyPath:@"playbackLikelyToKeepUp" options:NSKeyValueObservingOptionNew context:nil];

            updateCell.videoPlayer = [AVPlayer playerWithPlayerItem:updateCell.videoItem];
            updateCell.avLayer = [AVPlayerLayer playerLayerWithPlayer:updateCell.videoPlayer];
            updateCell.videoPlayer.actionAtItemEnd = AVPlayerActionAtItemEndNone;

            [[NSNotificationCenter defaultCenter] addObserver:updateCell selector:@selector(itemDidBufferPlaying:) name:AVPlayerItemPlaybackStalledNotification object:nil];
            [[NSNotificationCenter defaultCenter] addObserver:updateCell selector:@selector(itemDidFinishPlaying:) name:AVPlayerItemDidPlayToEndTimeNotification object:[updateCell.videoPlayer currentItem]];


            updateCell.avLayer.frame = updateCell.picture.bounds;
            [updateCell.videoView.layer addSublayer:updateCell.avLayer];

            [updateCell.avLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
            if(indexPath.row==0){
                [updateCell.videoPlayer play];
            }
        });
    });
    return updateCell;

}