ios14 - iOS 14 在后台播放视频中的音频

Question

iOS 14 在后台播放视频中的音频：当应用程序进入后台时音频暂停（即使我在 Capability 中打开了后台模式）。

如果 avPlayer 在前台播放，用户按下设备锁定按钮，它就会发生。

标签： ios14background-audio

Answer 1

如果您正在使用 avplayer 播放视频，并且还想在应用程序处于后台时播放音频。

试试这个代码，它适用于我的机器：

• Xcode 版本：12.0
• iOS版本：iOS 14

//first, observe the relative notification
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(applicationWillResignActive:)
                                                 name:UIApplicationWillResignActiveNotification object:nil];

    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(applicationWillEnterForeground:)
                                                 name:UIApplicationWillEnterForegroundNotification object:nil];


    //Add an observer to AVPlayerItem,this is the key point!!!
    [playerItem addObserver:self forKeyPath:@"playbackLikelyToKeepUp" options:NSKeyValueObservingOptionNew context:nil];

-(void)applicationWillResignActive:(NSNotification *)notification{
    //1 make sure the category of AVAudioSession is AVAudioSessionCategoryPlayback
    AVAudioSession *session=[AVAudioSession sharedInstance];
    [session setCategory:AVAudioSessionCategoryPlayback  error:nil];
    [session setActive:YES error:nil];
    
    //2 This is important!!!
    //set the avplayerlayer.player = nil.
    mavPlayerLayer.player = nil;
}


//when app becomes active,we should add the player to the avplayerlayer.
-(void)applicationWillEnterForeground:(NSNotification *)notification{
    // restore the avPlayerLayer.player
    mavPlayerLayer.player = mavPlayer;
}


- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context {
    if ([keyPath isEqualToString:@"playbackLikelyToKeepUp"]) {
        NSLog(@"playbackLikelyToKeepUp");
        [mavPlayer play];
    }
}

当然，不要忘记在 info.plist 文件中添加相关属性以支持后台播放。