ios - AVAudioPlayer 始终为 null，其 isPlaying 属性始终为 false。播放时文件混合

Question

过去三天我一直在拔头发来解决这个问题。我检查了很多示例代码，阅读了很多教程，在 stackoverflow 上搜索和检查了很多问题和答案，但我仍然无法解决问题。有几个类似的问题，如 this或 this但他们也没有任何解决方案。

关于我的项目:

我有一个 NIKMasterViewController 和一个 NIKDetailViewController。在第一个中，我在表格 View 中有一个音频文件列表；选择一行，它会导航到 NIKDetailViewController，用户可以在其中查看有关文件的一些信息并播放音频文件。我在 NIKMasterViewController 中定义了一个 AVAudioPlayer 属性并将其设置如下:NIKMasterViewController.h:

@property (nonatomic, strong) AVAudioPlayer *audioPlayer;

NIKMasterViewController.m:

@synthesize audioPlayer;

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([[segue identifier] isEqualToString:@"showDetail"])
    {
        NSIndexPath *indexPath = [self.tableView indexPathForCell:sender];
        NIKDetailViewController *detailViewController = (NIKDetailViewController *) segue.destinationViewController;
        [detailViewController setAudioPlayer:audioPlayer];

        [detailViewController setFeedEntry:[[[self feedParser] feedItems] objectAtIndex:indexPath.row]];

    } else {
        NSLog(@"Segue Identifier: %@", segue.identifier);
    }

}

这就是关于 NIKMasterViewController 中的 AVAudioPlayer 的全部内容。现在，在我的 NIKDetailViewController 中，我有了 AVAudioPlayer 的另一个属性:

NIKDetailViewController.h:

@property (nonatomic, strong) AVAudioPlayer *audioPlayer;

现在在我的 .m 文件中，我有一个名为 streamAudio 的方法，它在 viewDidLoad 中调用以准备音频播放，并且我有一个 if 条件要求检查 audioPlayer 是否为 nill，如果不是，则 audioPlayer.isPlaying 是否为 true 以便它停止 是播放器，但它从未被调用过，当我导航回 Master VC 以点击另一行以播放另一个文件时，第二个文件开始播放，而第一个文件正在播放，一切都变得困惑。

任何帮助将不胜感激，因为在数小时和数天后仍无法解决此问题后，我几乎要停止编程了!

NIKDetailViewController.m:

@synthesize audioPlayer;


- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
        selectedItem = [[NSString alloc]init];
    }
    return self;
}


#pragma mark - Managing the Audio Playback


- (IBAction)togglePlayingState:(id)button
{
    //Handle the button pressing
    [self togglePlayPause];
}



- (void)playAudio
{
    //Play the audio and set the button to represent the audio is playing
    [audioPlayer play];
    [playPauseButton setImage:[UIImage imageNamed:@"player_pause"] forState:UIControlStateNormal];
}

- (void)pauseAudio
{
    //Pause the audio and set the button to represent the audio is paused
    [audioPlayer pause];
    [playPauseButton setImage:[UIImage imageNamed:@"player_play"] forState:UIControlStateNormal];

}

- (void)togglePlayPause
{
    //Toggle if the music is playing or paused
    if (!audioPlayer.playing)
    {
        [self playAudio];
    }
    else if (audioPlayer.playing)
    {
        [self pauseAudio];
    }
}


- (void)streamAudio
{   
    currentFileName = [[feedEntry podcastDownloadURL] lastPathComponent];

    NSString* documentPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString* path = [documentPath stringByAppendingPathComponent:currentFileName];
    NSURL* audioURL = [NSURL fileURLWithPath: path];

    if (audioPlayer != nil)
    {
        if (audioPlayer.isPlaying)
        {
            [audioPlayer stop];  //THIS IS NEVER CALLED
        }
        audioPlayer = nil;           //THIS IS NEVER CALLED
    }

    audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:audioURL error:nil];

    // Set a timer which keep getting the current music time and update the UISlider in 1 sec interval
    playbackTimer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(updateSlider) userInfo:nil repeats:YES];
    // Set the maximum value of the UISlider
    seekSlider.maximumValue = audioPlayer.duration;


    currentTime.text = [NSString stringWithFormat:@"%d:%02d", (int)audioPlayer.currentTime / 60, (int)audioPlayer.currentTime % 60, nil];
    remainingTime.text = [NSString stringWithFormat:@"%d:%02d", (int)(audioPlayer.duration - audioPlayer.currentTime) / 60, (int)(audioPlayer.duration - audioPlayer.currentTime) % 60, nil];

    // Set the valueChanged target
    [seekSlider addTarget:self action:@selector(sliderChanged:) forControlEvents:UIControlEventValueChanged];
    audioPlayer.delegate = self;
    [audioPlayer prepareToPlay]; //Add the audio to the memory.
}


- (void)updateSlider
{
    // Update the slider about the music time
    seekSlider.value = audioPlayer.currentTime;
}

- (IBAction)sliderChanged:(UISlider *)sender {
    // Fast skip the music when user scrolls the slider
    [audioPlayer stop];
    [audioPlayer setCurrentTime:seekSlider.value];
    audioPlayer.delegate = self;

    [audioPlayer prepareToPlay];
    [audioPlayer play];
}

// Stop the timer when the music is finished (Need to implement the AVAudioPlayerDelegate in the Controller header)
- (void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag {
    // Music completed
    if (flag) {
        [playbackTimer invalidate];
    }
}


- (IBAction)forwardAudio:(id)sender
{
    int currentTime = [audioPlayer currentTime];
    [audioPlayer setCurrentTime:currentTime+10];
}

- (IBAction)rewindAudio:(id)sender
{
    int currentTime = [audioPlayer currentTime];
    [audioPlayer setCurrentTime:currentTime-10];
}


//Make sure we can recieve remote control events
- (BOOL)canBecomeFirstResponder {
    return YES;
}

- (void)remoteControlReceivedWithEvent:(UIEvent *)event {
    //if it is a remote control event handle it correctly
    if (event.type == UIEventTypeRemoteControl) {
        if (event.subtype == UIEventSubtypeRemoteControlPlay) {
            [self playAudio];
        } else if (event.subtype == UIEventSubtypeRemoteControlPause) {
            [self pauseAudio];
        } else if (event.subtype == UIEventSubtypeRemoteControlTogglePlayPause) {
            [self togglePlayPause];
        }
    }
}

#pragma mark - view life cycle


- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];

    //Once the view has loaded then we can register to begin recieving controls and we can become the first responder
    [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];
    [self becomeFirstResponder];
}

- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];

    //End recieving events
    [[UIApplication sharedApplication] endReceivingRemoteControlEvents];
    [self resignFirstResponder];
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    [self streamAudio];

    //Make sure the system follows our playback status - to support the playback when the app enters the background mode.
    [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];
    [[AVAudioSession sharedInstance] setActive: YES error: nil];

}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
@end

注意:我曾尝试将 Detail VC 中的属性设置为 weak 但随后，我收到警告，并且属性在我可以播放文件之前被释放.

Answer 1

所以...我终于可以通过创建 audioplayer 的 singleton 来解决这个问题。这是这样的:

1. 首先，我从我的 NIKMasterViewController 类中删除了所有与 audioPlayer 相关的代码，其中包括 audioPlayer 声明和设置在 prepareForSegue 中。
2. 我创建了一个名为 NIKAudioPlayer 的新类。

3. 在 NIKAudioPlayer.h 中:

   #import <Foundation/Foundation.h>
   #import <AVFoundation/AVFoundation.h>
   
   @interface NIKAudioPlayer : NSObject <AVAudioPlayerDelegate>
   {
       AVAudioPlayer *currentPlayer;
   }
   @property (nonatomic, strong) AVAudioPlayer *currentPlayer;
   +(NIKAudioPlayer *) sharedPlayer;
   -(void)playURL:(NSURL*)url;
   @end
   

4. 在 NIKAudioPlayer.m 中:

   #import "NIKAudioPlayer.h"
   
   @implementation NIKAudioPlayer 
   @synthesize currentPlayer;
   
   +(NIKAudioPlayer *) sharedPlayer
   {
       static NIKAudioPlayer* sharedPlayer;
       static dispatch_once_t onceToken;
       dispatch_once(&onceToken, ^{
       sharedPlayer = [[NIKAudioPlayer alloc] init];
       });
       return sharedPlayer;
   }
   
   -(void)playURL:(NSURL*)url
   {
       [currentPlayer stop];
       currentPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:nil];
       [currentPlayer prepareToPlay];
   }
   
   @end
   

5. 现在在代码的其他任何地方(在我的例子中是 NIKDetailViewController)每当我需要播放音频文件时，我从 调用 sharedPlayer >NIKAudioPlayer:

   [[NIKPlayer sharedPlayer] playURL:audioURL];
   [[NIKPlayer sharedPlayer].currentPlayer prepareToPlay];
   

简而言之，将 NIKDetailViewController 中的所有 audioPlayer 替换为 [NIKPlayer sharedPlayer].currentPlayer，甚至将其转换并使用它无处不在:

audioPlayer = [NIKPlayer sharedPlayer].currentPlayer