所以我有一个应用可以播放一堆歌曲，同时用户可以翻阅漫画书。我使用 AVAudioPlayer 并将其设置为按设定顺序播放歌曲。因此，当一首歌曲结束时，将播放下一首歌曲。当应用程序打开时，这可以完美运行。当应用程序处于后台时会出现问题。我将应用设置为在后台播放，效果很好。因此，当用户按下主屏幕时，音乐会继续播放。当歌曲结束时出现问题，假设像打开应用程序时一样播放下一首歌曲。相反什么也没有发生。根据我的 NSLog 语句，正在调用正确的方法但没有任何反应。这是我的代码:

- (void)audioPlayerDidFinishPlaying: (AVAudioPlayer *)player successfully: (BOOL) flag {

NSLog(@"Song finished");

if ([songSelect isEqualToString: @"01icecapades"]) {
    isPlay = @"yes";
    songSelect = @"02sugarcube";
    imageSelect = @"playbanner02";
    [self performSelector:@selector(triggerSong) withObject:nil afterDelay:0];
    [self performSelector:@selector(triggerBanner) withObject:nil afterDelay:0];
}
else if ([songSelect isEqualToString: @"02sugarcube"]) {
    isPlay = @"yes";
    songSelect = @"03bullets";
    imageSelect = @"playbanner03";
    [self performSelector:@selector(triggerSong) withObject:nil afterDelay:0];
    [self performSelector:@selector(triggerBanner) withObject:nil afterDelay:0];
}
else if ([songSelect isEqualToString: @"03bullets"]) {
    isPlay = @"yes";
    songSelect = @"04satanama";
    imageSelect = @"playbanner04";
    [self performSelector:@selector(triggerSong) withObject:nil afterDelay:0];
    [self performSelector:@selector(triggerBanner) withObject:nil afterDelay:0];
}
else if ([songSelect isEqualToString: @"04satanama"]) {
    isPlay = @"yes";
    songSelect = @"05uglyjoke";
    imageSelect = @"playbanner05";
    [self performSelector:@selector(triggerSong) withObject:nil afterDelay:0];
    [self performSelector:@selector(triggerBanner) withObject:nil afterDelay:0];
}
else if ([songSelect isEqualToString: @"05uglyjoke"]) {
    isPlay = @"yes"; 
    songSelect = @"01icecapades";
    imageSelect = @"playbanner01";
    [self performSelector:@selector(triggerSong) withObject:nil afterDelay:0];
    [self performSelector:@selector(triggerBanner) withObject:nil afterDelay:0];
}}

上面是识别正在播放的歌曲的代码，然后设置正确的歌曲。然后它会触发另一种设置播放器的方法。

- (void)triggerSong {
NSLog(@"triggerSong called");
NSString       *path;
NSError        *error;
// Path the audio file
path = [[NSBundle mainBundle] pathForResource:songSelect ofType:@"mp3"];
// If we can access the file...
if ([[NSFileManager defaultManager] fileExistsAtPath:path]) 
{    
    // Setup the player
    player = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:path] error:&error];
    //player = [initWithContentsOfURL:[NSURL fileURLWithPath:path] error:&error];
    [player setDelegate: self];
    // Set the volume (range is 0 to 1)
    player.volume = 1.0f;     
    [player prepareToPlay];
    [player setNumberOfLoops:0];
    [player play];
    NSLog(@"player play");
    [error release];
    player.delegate = self;
    // schedules an action every second for countdown
    [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(updateTimeLeft) userInfo:nil repeats:YES];
}}

现在我假设这不是执行此操作的最佳方法，但当应用程序处于前台状态时效果很好。我一直在查看文档，但似乎找不到导致此问题的原因。我希望有人能看出我的方法有误。就像我之前说的，正在调用 triggerSong 方法中的两个 NSLog，所以我不明白为什么 AVAudioPlayer (player) 没有被调用。

我的 info.plist 中也有正确的设置，我的 viewDidLoad 中也有这个:

//Make sure the system follows our playback status
[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];
[[AVAudioSession sharedInstance] setActive: YES error: nil];

感谢任何见解。非常感激。

最佳答案

Relevant discussion

简短回答:

您需要在第一个 View Controller 的 init 或 viewDidLoad 方法中使用此代码:

[[UIApplication sharedApplication] beginReceivingRemoteControlEvents];

带样本的长答案:

这是我的例子。和你一样，我从一个可以在后台播放音乐但在第一个剪辑结束后就再也无法继续播放的应用程序开始。我复制了原始 Music.mp3 并将其命名为 Music2.mp3。我的意图是在 Music.mp3 结束后立即播放 Music2.mp3 (audioPlayerDidFinishPlaying:)。我在后台任务中闲逛了一段时间，直到我在没有后台任务的情况下工作:

-(id)init{
    self = [super initWithNibName:@"MediaPlayerViewController" bundle:nil];
    if(self){

        //Need this to play background playlist
        [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];

        //MUSIC CLIP
        //Sets up the first song...
        NSString *musicPath = [[NSBundle mainBundle] pathForResource:@"Music" ofType:@"mp3"];
        if(musicPath){
            NSURL *musicURL = [NSURL fileURLWithPath:musicPath];
            audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:musicURL error:nil]; 
            [audioPlayer setDelegate:self];
        }
    }
    return self;
}


-(IBAction)playAudioFile:(id)sender{

    if([audioPlayer isPlaying]){
        //Stop playing audio and change test of button
        [audioPlayer stop];
        [sender setTitle:@"Play Audio File" forState:UIControlStateNormal];
    }
    else{
        //Start playing audio and change text of button so
        //user can tap to stop playback
        [audioPlayer play];
        [sender setTitle:@"Stop Audio File" forState:UIControlStateNormal];
    }
}


-(void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag{
    [audioButton setTitle:@"Play Audio File" forState:UIControlStateNormal];
    [playRecordingButton setTitle:@"Play Rec File" forState:UIControlStateNormal];

    //PLAY THE SECOND SONG
    NSString *musicPath2 = [[NSBundle mainBundle] pathForResource:@"Music2" ofType:@"mp3"];
    if(musicPath2){

        NSURL *musicURL2 = [NSURL fileURLWithPath:musicPath2];
        audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:musicURL2 error:nil];
        [audioPlayer setDelegate:self];
        NSLog(@"Play it again: \n%@", musicPath2);
        [audioPlayer play];
    } 
}

最终结果是我的应用程序现在正在连续循环播放 Music2.mp3，即使该应用程序在后台也是如此。

关于iOS - AVAudioPlayer 在后台时不会继续播放下一首歌曲，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/9660488/