you dont need to an asset. the movie is like any other filetype an attachment and for that you need only the url. do the following:
in your .h file:
@property (nonatomic, retain) NSURL *fileURL;
in your .m file: instead of
NSURL *_URL=(NSURL*)[info objectForKey:UIImagePickerControllerMediaURL];
use
self.fileURL = (NSURL*)[info objectForKey:UIImagePickerControllerMediaURL];
and instead of
NSURL *url = _URL;
AVURLAsset *anAsset = [[AVURLAsset alloc] initWithURL:url options:nil];
NSArray *activityItems = [NSArray arrayWithObjects:shareString, anAsset, nil];
simply use:
NSArray *activityItems = [NSArray arrayWithObjects:shareString, self.fileURL, nil];