Question

I have an audio player that I’m building using AVPlayer.

Currently, I keep the player instance around and when I need to swap tracks (either from a manual selection or the track has reached the end) I create a new AVPlayerItem and I call replaceCurrentItemWithPlayerItem with the new item.

According to the docs, replaceCurrentItemWithPlayerItem is an asynchronous operation, so I also observe the currentItem key path of the player. When that gets called, I tell my player to play.

Here is the relevant code:

AVPlayerItem *playerItem = [AVPlayerItem playerItemWithAsset:asset];
[playerItem addObserver:self forKeyPath:@"status" options:NSKeyValueObservingOptionNew context:CHStreamingAudioPlayer_PlayerItemStatusChangedContext];

if (!_player) {
    _player = [[AVPlayer alloc] initWithPlayerItem:playerItem]; 
    [_player addObserver:self forKeyPath:@"status"          options:NSKeyValueObservingOptionNew context:CHStreamingAudioPlayer_PlayerStatusChangedContext];
    [_player addObserver:self forKeyPath:@"currentItem"     options:NSKeyValueObservingOptionNew context:CHStreamingAudioPlayer_PlayerCurrentItemChangedContext];
} else {
    [_player replaceCurrentItemWithPlayerItem:playerItem];
}

And here is the key value observation callback:

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
    if (context == CHStreamingAudioPlayer_PlayerCurrentItemChangedContext) {
        NSLog(@"Player's current item changed! Change dictionary: %@", change);
        if (_player.currentItem) {
            [self play]; //<---- doesn't get called
        }
    } else {
        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
    }
}

On iOS 4.3.3 (and iOS 5) my key observation method is called but _player.currentItem is always nil. On 4.2.1 and 4.3.2 this property contains the actual value. This method is never called again. So in essence, replacing seems to always fail.

This seems like a bug, but perhaps I’m doing something wrong.

Answer 1

I had this issue with iOS 5 (including 5.0.1). It used to work fine on iOS 4.x.

There are two ways to workaround this, release and recreate your AVPlayer with the desired AVPlayerItems each time you need to swap tracks. Or, simply call replaceCurrentItemWithPlayerItem: on the main thread.

I tried both options and they worked fine.

Credits to: Apple Developer Forums