iOS版 - AVAudioPlayer不会继续下一首歌曲，而在后台 [英] iOS - AVAudioPlayer doesn't continue to next song while in background

问题描述

所以我有一个播放一堆歌曲，而用户可以通过一本漫画书翻页的应用程序。我用AVAudioPlayer，我有它设置了一组以播放歌曲。所以，当一首歌曲结束后，下一个会玩。这完美的作品时，应用程序是开放的。当应用程序在后台出现问题。我成立了应用程序在后台播放，并且工作正常。因此，当用户presses主屏幕的音乐继续播放。当歌曲结束时，会出现问题，这是假设像它时，应用程序是开放的播放下一首歌曲。相反，没有任何反应。按照我的NSLog语句正确的方法被调用，但没有任何反应。这里是我的code：

So I have an app that plays a bunch of songs while the user can flip through a comic book. I use AVAudioPlayer and I have it set up to play the songs in a set order. So when one song finishes, the next one will play. This works flawlessly when the app is open. The problem occurs when the app is in the background. I set up the app to play in the background, and that works fine. So when the user presses the home screen the music continues to play. The problem occurs when the song ends, it is suppose to play the next song like it does when the app is open. Instead nothing happens. According to the my NSLog statements the correct methods are being called but nothing happens. Here is my code:

- (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];
}}

以上是code识别哪些歌曲播放，并设置下一个正确的歌曲。然后，它会触发，设置了玩家的另一种方法。

Above is the code that recognizes which song is playing, and sets the correct song next. Then it triggers another method that sets up the player.

- (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];
}}

现在我假定这是不是这样做的最佳方式，但是当应用程序在前台状态下，它的伟大工程。我一直在寻找通过的文件和我似乎无法找到这个问题的原因。我希望有人也许能够看到一个错误我的方法。就像我之前说的，在triggerSong方法两个NSLogs被调用，所以我不明白为什么AVAudioPlayer（播放器）不会被调用。

Now I assuming this is not the best way to do this, but it works great when the app is in the foreground state. I've been looking through the documentation and I can't seem to find the cause of this problem. I was hoping somebody might be able to see an error to my approach. Like I said before, the two NSLogs in the triggerSong method are being called so I can't see why the AVAudioPlayer (player) is not being called.

我也有我的info.plist正确的设置，我有这在我的viewDidLoad中：

Also I have the correct setting in my info.plist and I have this in my viewDidLoad:

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

感谢您的任何见解。大部分AP preciated。

Thanks for any insight. Much appreciated.

推荐答案

答案很简单：

您需要或者您的第一个视图控制器的init或viewDidLoad方法本code：

You need this code in either your first view controller's init or viewDidLoad method:

[[UIApplication sharedApplication] beginReceivingRemoteControlEvents];

---

长的答案W /示例：

---

LONG ANSWER W/ SAMPLE:

下面是我的榜样。和你一样，我开始和一个应用程序，会在后台播放音乐，但永远无法继续播放第一个剪辑结束之后。我做了原有的music.mp3的副本，并把它命名为Music2.mp3。我的目的是尽快结束的music.mp3（audioPlayerDidFinishPlaying :)玩Music2.mp3。我疯玩与周围的后台任务了一段时间，直到我得到这个工作没有后台任务：

Here is my example. Like you, I began with an app that would play music in the background but could never continue playing after the first clip ended. I made a copy of the original Music.mp3 and named it Music2.mp3. My intention was to play Music2.mp3 as soon as Music.mp3 ended (audioPlayerDidFinishPlaying:). I goofed around with the background tasks for awhile until I got this working WITHOUT the background task:

-(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];
    } 
}

最终的结果是，我的应用程序现在开始连续循环播放Music2.mp3，即使该应用程序是在后台。

The end result is that my app is now playing Music2.mp3 on a continuous loop, even if the app is in the background.

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