IOS:MPMediaItems原始歌曲转换为NSData

Question

我使用了这个代码这很好，但是转换成数据后，当我试图将转换后的数据发送到MFMailComposeViewController或MFMessageComposeViewController时，它有时会以文档格式出现，但未能获得mp3格式。当我播放我们发送给MFmailComposeViewcontroller或MFMessageComposeViewController的歌曲时，正确转换的歌曲正在正确播放，但有些正在转换为文档格式。如何克服这一点。请推荐我。

SelectedAlbumUrl = [[arr_tablVArray] objectAtIndex:indexPath。行]objectForKey: @"SongUrl");

这个方法像这样调用。

[self mediaItemToData:[arr_tablVArray objectAtIndex:indexPath.row]];
-(void)mediaItemToData : (MPMediaItem * ) curItem
{
    NSURL *url = SelectedAlbumUrl;
    AVURLAsset *songAsset = [AVURLAsset URLAssetWithURL: url options:nil];
    AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset: songAsset
                                                                      presetName:AVAssetExportPresetAppleM4A];
    exporter.outputFileType =   @"com.apple.m4a-audio";
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString * myDocumentsDirectory = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;
    [[NSDate date] timeIntervalSince1970];
    NSTimeInterval seconds = [[NSDate date] timeIntervalSince1970];
    NSString *intervalSeconds = [NSString stringWithFormat:@"%0.0f",seconds];
    NSString * fileName = [NSString stringWithFormat:@"%@.caf",intervalSeconds];
    NSLog(@"the file name is --->%@",fileName);
    NSString *exportFile = [myDocumentsDirectory stringByAppendingPathComponent:fileName];
    exportURL = [NSURL fileURLWithPath:exportFile];
    exporter.outputURL = exportURL;
    // (completion handler block omitted)
    [exporter exportAsynchronouslyWithCompletionHandler:
     ^{
         int exportStatus = exporter.status;
         switch (exportStatus)
         {
             case AVAssetExportSessionStatusFailed:
             {
                 NSError *exportError = exporter.error;
                 NSLog (@"AVAssetExportSessionStatusFailed: %@", exportError);
                 break;
             }
             case AVAssetExportSessionStatusCompleted:
             {
                 NSLog (@"AVAssetExportSessionStatusCompleted");
                 NSData *data = [NSData dataWithContentsOfFile: [myDocumentsDirectory
                                                                 stringByAppendingPathComponent:fileName]];
                 data = nil;
                 break;
             }
             case AVAssetExportSessionStatusUnknown:
             {
                 NSLog (@"AVAssetExportSessionStatusUnknown"); break;
             }
             case AVAssetExportSessionStatusExporting:
             {
                 NSLog (@"AVAssetExportSessionStatusExporting"); break;
             }
             case AVAssetExportSessionStatusCancelled:
             {
                 NSLog (@"AVAssetExportSessionStatusCancelled"); break;
             }
             case AVAssetExportSessionStatusWaiting:
             {
                 NSLog (@"AVAssetExportSessionStatusWaiting"); break;
             }
             default:
             {
                 NSLog (@"didn't get export status"); break;
             }
         }
     }];
}
After that url converting to NSData sending through email,message and airdrop like this 
NSData *Data = [NSData dataWithContentsOfURL:exportURL];
        [composer addAttachmentData:Data mimeType:@".caf" fileName:str_songtitle];

Answer 1

试试这个

- (void)addAttachmentData:(NSData*)attachment mimeType:(NSString*)mimeType fileName:(NSString*)filename

with mimeType = audio/mpeg