AVPlayer replaceCurrentItemWithPlayerItem不适用于iOS 4.3.3+ [英] AVPlayer replaceCurrentItemWithPlayerItem not working on iOS 4.3.3+

问题描述

我有一个使用AVPlayer构建的音频播放器。

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

目前，我保留播放器实例和我需要交换轨道时（从手动选择或轨道到达结束）我创建一个新的 AVPlayerItem 我打电话给 replaceCurrentItemWithPlayerItem 使用新项。

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.

根据文档， replaceCurrentItemWithPlayerItem 是异步的操作，所以我也观察了播放器的 currentItem 键路径。当它被调用时，我告诉我的玩家玩。

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.

以下是相关代码：

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];
}

这是键值观察回调：

- (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];
    }
}

在iOS 4.3.3（和iOS 5）上我的调用密钥观察方法，但 _player.currentItem 总是 nil 。在4.2.1和4.3.2上，此属性包含实际值。永远不会再调用此方法。所以从本质上讲，替换似乎总是失败。

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.

这似乎是一个错误，但也许我做错了。

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

推荐答案

我在iOS 5（包括5.0.1）中遇到过这个问题。它曾经在iOS 4.x上正常工作。

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

有两种解决方法，使用所需的释放并重新创建 AVPlayer 每次需要交换曲目时，AVPlayerItem s。或者，只需在主线程上调用 replaceCurrentItemWithPlayerItem：。

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.

我尝试了两种选择，但它们运行良好。

I tried both options and they worked fine.

致记： Apple Developer论坛

这篇关于AVPlayer replaceCurrentItemWithPlayerItem不适用于iOS 4.3.3+的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！