Saving audio files and navigating between views - iphone

Question

I'm having trouble saving recorded audio files and playing them back after navigating between views.
I've been using the tutorial at http://www.techotopia.com/index.php/Recording_Audio_on_an_iPhone_with_AVAudioRecorder_%28iOS_4%29
I've added in a line to save the audio file, so my prepareForAudioRecording looks like the code below. This method is called in viewDidLoad.
-(void) prepareForAudioRecording
{
btnPlay.enabled = NO;
btnStop.enabled = NO;
NSArray *dirPaths;
NSString *docsDir;
dirPaths = NSSearchPathForDirectoriesInDomains(
NSDocumentDirectory, NSUserDomainMask, YES);
docsDir = [dirPaths objectAtIndex:0];
NSString *soundFilePath = [docsDir
stringByAppendingPathComponent:#"page1.caf"];
//this line added to save the audio file
[audioPlayer.data writeToFile:soundFilePath atomically:YES];
NSURL *soundFileURL = [NSURL fileURLWithPath:soundFilePath];
NSDictionary *recordSettings = [NSDictionary
dictionaryWithObjectsAndKeys:
[NSNumber numberWithInt:AVAudioQualityMin],
AVEncoderAudioQualityKey,
[NSNumber numberWithInt:16],
AVEncoderBitRateKey,
[NSNumber numberWithInt: 2],
AVNumberOfChannelsKey,
[NSNumber numberWithFloat:44100.0],
AVSampleRateKey,
nil];
NSError *error = nil;
audioRecorder = [[AVAudioRecorder alloc]
initWithURL:soundFileURL
settings:recordSettings
error:&error];
if (error)
{
NSLog(#"error: %#", [error localizedDescription]);
} else {
[audioRecorder prepareToRecord];
}
}
As I said, i can record the audio and then play back the audio while in the same view controller, but when i navigate away from the view and return to it I can't playback the recording.
Firstly the play and stop buttons were disabled, which i thought should have only happen when the view was first loaded - but even when i enabled them and pressed the play button, there was no audio.
My other methods are below for my play, stop and record button.
- (IBAction)playAudio:(id)sender {
if (!audioRecorder.recording)
{
btnStop.enabled = YES;
btnRecord.enabled = NO;
//if (audioPlayer)
//[audioPlayer release];
NSError *error;
audioPlayer = [[AVAudioPlayer alloc]
initWithContentsOfURL:audioRecorder.url
error:&error];
audioPlayer.delegate = self;
if (error)
NSLog(#"Error: %#",
[error localizedDescription]);
else
[audioPlayer play];
}
}
-(void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag
{
btnRecord.enabled = YES;
btnStop.enabled = NO;
}
-(void)audioPlayerDecodeErrorDidOccur:(AVAudioPlayer *)player error:(NSError *)error
{
NSLog(#"Decode Error occurred");
}
-(void)audioRecorderDidFinishRecording:(AVAudioRecorder *)recorder successfully:(BOOL)flag
{
}
-(void)audioRecorderEncodeErrorDidOccur:(AVAudioRecorder *)recorder error:(NSError *)error
{
NSLog(#"Encode Error occurred");
}
- (IBAction)recordAudio:(id)sender {
if (!audioRecorder.recording)
{
btnPlay.enabled = NO;
btnStop.enabled = YES;
[audioRecorder record];
}
}
- (IBAction)stopAudio:(id)sender {
btnStop.enabled = NO;
btnPlay.enabled = YES;
btnRecord.enabled = YES;
if (audioRecorder.recording)
{
[audioRecorder stop];
} else if (audioPlayer.playing) {
[audioPlayer stop];
}
}
I know there's a lot of code to look at there but if i'm missing out anything please let me know. I'd really appreciate any help with this, thanks.
EDIT 1: Ok, i've done a bit more investigating and opened up the folder where my audio files are saved. The audio records fine and the file size is around 400KB. When i push to the next view controller the filesize remains at 400KB. But as soon as i press my back button (not the preprogrammed one in the nav bar) the filesize goes to 4KB; an empty file. The code for my back button is simply:
- (IBAction)backPressed:(id)sender {
[self.navigationController popViewControllerAnimated:YES];
}
Please help!
EDIT 2: It also happens with the back button in the nav bar too.

Answer 1

You're allocating audioPlayer with audioRecorder.url. If something happend to audioRecorder it's url might be invalid.
Try setting audioPlayer this way:
- (IBAction)playAudio:(id)sender {
if (!audioRecorder.recording)
{
btnStop.enabled = YES;
btnRecord.enabled = NO;
NSArray *dirPaths;
NSString *docsDir;
dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
docsDir = [dirPaths objectAtIndex:0];
NSString *soundFilePath = [docsDir stringByAppendingPathComponent:#"page1.caf"];
NSURL *soundFileURL = [NSURL fileURLWithPath:soundFilePath];
NSError *error;
audioPlayer = [[AVAudioPlayer alloc] nitWithContentsOfURL:soundFileUR
error:&error];
audioPlayer.delegate = self;
if (error)
NSLog(#"Error: %#",[error localizedDescription]);
else
[audioPlayer play];
}
}