如何使用MPMediaPickerController从iPod库录制歌曲播放？

我正在制作一个应用程序，在该应用程序中，我必须使用MPMediaPickerController播放iPod音乐库中的音乐。播放一首歌曲后，我想用某种外部语音录制歌曲（例如： - 用户的声音）。我试图做相同但出现问题的应用程序首先启动，我从iPod音乐库中选择一首歌曲后，我点击开始录制按钮。当我点击开始录制按钮时，我播放的歌曲停止前，但录制工作正常。录制的用户的声音工作正常，但歌曲没有得到记录，因为当我点击“开始录制”按钮时，我告诉歌曲停止。我正在使用AVAudioRecorder进行录制。这是我正在使用的代码。如何使用MPMediaPickerController从iPod库录制歌曲播放？

-(Void)ViewDidLoad 
{ 
self.musicPlayer = [MPMusicPlayerController iPodMusicPlayer]; 
} 
- (void)playOrPauseMusic:(id)sender { 
MPMusicPlaybackState playbackState = self.musicPlayer.playbackState; 
if (playbackState == MPMusicPlaybackStateStopped || playbackState == MPMusicPlaybackStatePaused) { 
    [self.musicPlayer play]; 
} else if (playbackState == MPMusicPlaybackStatePlaying) { 
    [self.musicPlayer pause]; 
} 
} 

- (void)openMediaPicker:(id)sender { 
MPMediaPickerController *mediaPicker = [[MPMediaPickerController alloc] initWithMediaTypes:MPMediaTypeMusic]; 
mediaPicker.delegate = self; 
mediaPicker.allowsPickingMultipleItems = NO; // this is the default 
[mediaPicker shouldAutorotateToInterfaceOrientation:UIInterfaceOrientationLandscapeRight]; 
[self presentModalViewController:mediaPicker animated:YES]; 
} 

- (void) startRecording 
{ 
[self.musicPlayer play]; 
AVAudioSession *audioSession = [AVAudioSession sharedInstance]; 
NSError *err = nil; 
[audioSession setCategory :AVAudioSessionCategoryPlayAndRecord error:&err]; 
if(err){ 
    NSLog(@"audioSession: %@ %d %@", [err domain], [err code], [[err userInfo] description]); 
    return; 
} 
[audioSession setActive:YES error:&err]; 
err = nil; 
if(err){ 
    NSLog(@"audioSession: %@ %d %@", [err domain], [err code], [[err userInfo] description]); 
    return; 
} 

recordSetting = [[NSMutableDictionary alloc] init]; 

// We can use kAudioFormatAppleIMA4 (4:1 compression) or kAudioFormatLinearPCM for nocompression 
[recordSetting setValue :[NSNumber numberWithInt:kAudioFormatAppleIMA4] forKey:AVFormatIDKey]; 

// We can use 44100, 32000, 24000, 16000 or 12000 depending on sound quality 
[recordSetting setValue:[NSNumber numberWithFloat:44100.0] forKey:AVSampleRateKey]; 

// We can use 2(if using additional h/w) or 1 (iPhone only has one microphone) 
[recordSetting setValue:[NSNumber numberWithInt: 1] forKey:AVNumberOfChannelsKey]; 

[recordSetting setObject:[NSNumber numberWithInt:12800] forKey:AVEncoderBitRateKey]; 
[recordSetting setObject:[NSNumber numberWithInt:16] forKey:AVLinearPCMBitDepthKey]; 
[recordSetting setObject:[NSNumber numberWithInt: AVAudioQualityMax] forKey: AVEncoderAudioQualityKey]; 

recorderFilePath = [NSString stringWithFormat:@"%@/MySound.caf", DOCUMENTS_FOLDER] ; 

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

NSURL *url = [NSURL fileURLWithPath:recorderFilePath]; 

err = nil; 

NSData *audioData = [NSData dataWithContentsOfFile:[url path] options: 0 error:&err]; 
if(audioData) 
{ 
    NSFileManager *fm = [NSFileManager defaultManager]; 
    [fm removeItemAtPath:[url path] error:&err]; 
} 

err = nil; 
recorder = [[ AVAudioRecorder alloc] initWithURL:url settings:recordSetting error:&err]; 
if(!recorder){ 
    NSLog(@"recorder: %@ %d %@", [err domain], [err code], [[err userInfo] description]); 
    UIAlertView *alert = 
    [[UIAlertView alloc] initWithTitle: @"Warning" 
           message: [err localizedDescription] 
           delegate: nil 
        cancelButtonTitle:@"OK" 
        otherButtonTitles:nil]; 
    [alert show]; 

    return; 
} 

//prepare to record 
[recorder setDelegate:self]; 
[recorder prepareToRecord]; 
recorder.meteringEnabled = YES; 

BOOL audioHWAvailable = audioSession.inputIsAvailable; 
if (! audioHWAvailable) { 
    UIAlertView *cantRecordAlert = 
    [[UIAlertView alloc] initWithTitle: @"Warning" 
           message: @"Audio input hardware not available" 
           delegate: nil 
        cancelButtonTitle:@"OK" 
        otherButtonTitles:nil]; 
    [cantRecordAlert show]; 

    return; 
} 

// start recording 
[recorder recordForDuration:(NSTimeInterval) 2]; 

lblStatusMsg.text = @"Recording..."; 
selector:@selector(handleTimer) userInfo:nil repeats:YES]; 
}

这是我的代码MPMusicPlayer和AVAudioRecorder.Please help.Thanks提前。

来源

2012-04-06 Nikhil Bansal