iphone - 为什么 AVAudioRecorderprepareToRecord 失败？

Question

我正在尝试设置一个基本 Controller 来记录用户音频输入(语音)。但是，AVAudioRecorder 的prepareToRecord 方法失​​败了，我不明白为什么。我已在应用程序委托(delegate)中设置了 Audio Session ，并且在实例化 AVAudioRecorder 实例时没有收到错误:

//应用程序委托(delegate)片段

AVAudioSession* audioSession = [AVAudioSession sharedInstance];
NSError* audioSessionError   = nil;

[audioSession setCategory: AVAudioSessionCategoryPlayAndRecord
                  error: &audioSessionError];

  if (audioSessionError) {
    NSLog (@"Error setting audio category: %@", [audioSessionError localizedDescription]); 
} else {
  NSLog(@"No session errors for setting category");
}

[audioSession setActive:YES error:&audioSessionError];

if (audioSessionError) {
  NSLog (@"Error activating audio session: %@", [audioSessionError localizedDescription]); 
} else {
NSLog(@"no session errors for setActive");
}

//查看是否已加载到 RECORDERCONTROLLER

- (void)viewDidLoad {

self.navigationItem.title = [NSString stringWithFormat:@"%@", [[MyAppDelegate loadApplicationPlist] valueForKey:@"recorderViewTitle"]];

self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone 
                                                                                     target:self 
                                                                                     action:@selector(dismiss)];

[self alertIfNoAudioInput];

 [self createAVAudioRecorder];

 minutesSecondsFormatter = [[SimpleMinutesSecondsFormatter alloc] init];
currentTimeUpdateTimer  = [NSTimer scheduledTimerWithTimeInterval:0.1
                                                        target:self selector:@selector(updateAudioDisplay)
                                                       userInfo:NULL repeats:YES];

[super viewDidLoad];
}

//创建 AVAUDIORECORDER

- (NSError *)createAVAudioRecorder {

NSError *recorderSetupError = nil;

 [audioRecorder release];
audioRecorder = nil;

 NSString *timestamp = [NSString stringWithFormat:@"%d", (long)[[NSDate date] timeIntervalSince1970]];

 NSString *destinationString = [[MyAppDelegate getAppDocumentsDirectory] stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.caf", timestamp]];
 NSLog(@"destinationString: %@", destinationString);
 NSURL *destinationUrl       = [NSURL fileURLWithPath: destinationString];

 audioRecorder = [[AVAudioRecorder alloc] initWithURL:destinationUrl 
                                          settings:[[AVRecordSettings sharedInstance] getSettings] 
                                             error:&recorderSetupError];

if (recorderSetupError) {

   UIAlertView *cantRecordAlert =
    [[UIAlertView alloc] initWithTitle:@"Can't record"
                           message:[recorderSetupError localizedDescription]
                          delegate:nil
                 cancelButtonTitle:@"OK"
                 otherButtonTitles:nil];
    [cantRecordAlert show];
    [cantRecordAlert release];
    return recorderSetupError;
} else {
  NSLog(@"no av setup error");
}

if ([audioRecorder prepareToRecord]) {
  recordPauseButton.enabled = YES;
  audioRecorder.delegate    = self;
 } else {
  NSLog(@"couldn't prepare to record");
 }

 NSLog (@"recorderSetupError: %@", recorderSetupError);

 return recorderSetupError;
 }

Answer 1

如果您尝试保存文件的目录不存在，则prepareToRecord也会失败(静默地，没有错误)。使用 NSFileManager 检查目录是否已经存在。