AVAudioPlayer 暂停问题

Question

在我的项目中，我有一个播放歌曲的 AVAudioPlayer。在我暂停它并再次点击播放后，它会重新开始，而不是在我暂停的地方播放。为什么会这样？ 此外，当我第一次按播放时，它会加载大约 3-4 秒的歌曲。我以为我通过在另一个线程上加载它来解决它，但它仍然加载得太慢（至少视图不再冻结）。我该如何解决？代码如下：

- (IBAction)play:(id)sender {
  songIsCurrentlyPaused = NO;
  if(songIsCurrentlyPaused==YES){
    [self.background play];
  } else {
    playQueue = dispatch_queue_create("volume_change", NULL);
    dispatch_async(playQueue, ^{ NSString *filePath = 
      [[NSBundle mainBundle]pathForResource:@"some_song" ofType:@"mp3"];
      NSURL *fileURL = [[NSURL alloc] initFileURLWithPath:filePath];
      self.background = [[AVAudioPlayer alloc] initWithContentsOfURL:fileURL error:nil];
      self.background.delegate = self;
      [self.background setNumberOfLoops:1];
      [self.background setVolume:0.5];
      [self.background play]; });

      [trackNameLabel setText:@"Currently playing :\n some_song"];
      self.timer = [NSTimer scheduledTimerWithTimeInterval:0.25 target:self selector:@selector(updateProgressBar) userInfo:nil repeats:YES];
    }
}

- (IBAction)pause:(id)sender {
  songIsCurrentlyPaused = YES;
  [self.background pause];
  [trackNameLabel setText:@"Currently playing : some_song (paused)"];
  [self.progressBar setProgress:self.background.currentTime/self.background.duration animated:YES];
}

谢谢！

Answer 1

您在play: 的开头将songIsCurrentlyPaused 设置为NO

尝试将其注释掉：

- (IBAction)play:(id)sender {
  //songIsCurrentlyPaused = NO;
  if(songIsCurrentlyPaused==YES){
    [self.background play];
  } else {
    playQueue = dispatch_queue_create("volume_change", NULL);
    dispatch_async(playQueue, ^{ NSString *filePath = 
      [[NSBundle mainBundle]pathForResource:@"some_song" ofType:@"mp3"];
      NSURL *fileURL = [[NSURL alloc] initFileURLWithPath:filePath];
      self.background = [[AVAudioPlayer alloc] initWithContentsOfURL:fileURL error:nil];
      self.background.delegate = self;
      [self.background setNumberOfLoops:1];
      [self.background setVolume:0.5];
      [self.background play]; });

      [trackNameLabel setText:@"Currently playing :\n some_song"];
      self.timer = [NSTimer scheduledTimerWithTimeInterval:0.25 target:self selector:@selector(updateProgressBar) userInfo:nil repeats:YES];
    }
}

- (IBAction)pause:(id)sender {
  songIsCurrentlyPaused = YES;
  [self.background pause];
  [trackNameLabel setText:@"Currently playing : some_song (paused)"];
  [self.progressBar setProgress:self.background.currentTime/self.background.duration animated:YES];
}

如果您想摆脱最初的停顿，您将不得不完全重新组织您的播放器设置。在用户点击播放按钮并调用之前对其进行初始化：

[self.background prepareToPlay];

这将预加载歌曲。还将songIsCurrentlyPaused = NO; 移动到代码中的某个较早位置。

编辑：

要消除初始延迟，您应该将初始化代码移至 loadView 或 viweDidLoad 之类的地方。

   //initialization code
   NSString *filePath = [[NSBundle mainBundle]pathForResource:@"some_song" ofType:@"mp3"];
   NSURL *fileURL = [[NSURL alloc] initFileURLWithPath:filePath];
   self.background = [[AVAudioPlayer alloc] initWithContentsOfURL:fileURL error:nil];
   self.background.delegate = self;
   [self.background setNumberOfLoops:1];
   [self.background setVolume:0.5];
   [self.background prepareToPlay];

现在这可能会导致 UI 显示滞后，因此您可能不想考虑预加载数据 在后台线程中。

你的IBAction 方法应该被修改：

- (IBAction)play:(id)sender
{

   if (songIsCurrentlyPaused==YES) 
   { 
      [self.background play];
   }
   else
   {
      playQueue = dispatch_queue_create("volume_change", NULL);
      dispatch_async(playQueue, ^{
         [self.background setCurrentTime: 0.0];
         [self.background play];
      });

      [self.progressBar setProgress:0.0 animated:YES];
      [trackNameLabel setText:@"Currently playing :\n some_song"];
      self.timer = [NSTimer scheduledTimerWithTimeInterval:0.25 target:self selector:@selector(updateProgressBar) userInfo:nil repeats:YES];

  }
  songIsCurrentlyPaused = NO;
}

- (IBAction)pause:(id)sender
{
  songIsCurrentlyPaused = YES;
  [self.background pause];
  [trackNameLabel setText:@"Currently playing : some_song (paused)"];
  [self.progressBar setProgress:self.background.currentTime/self.background.duration animated:YES];
}