UIActivityViewController Gmail共享主题和正文相同

我正在分享一些内容UIActivityController.

它适用于其他选项.

我能得到subject并且body在默认的邮件应用程序.

但当我用来共享内容时,gmail我Subject的邮件已经消失,我Body在Gmail Subject's部分获取内容:

这是我的代码:

    NSString *body = @"I am Body";
NSString *tagLine = @"I am Subject";

   NSArray *objectToShare = [NSArray arrayWithObjects:body, nil];
UIActivityViewController *activityVC = [[UIActivityViewController alloc] initWithActivityItems:objectToShare applicationActivities:nil];

[activityVC setValue:tagLine forKey:@"subject"];

NSArray *excludeActivities = @[UIActivityTypeAirDrop,
                               UIActivityTypePrint,
                               UIActivityTypeAssignToContact,
                               UIActivityTypeSaveToCameraRoll,
                               UIActivityTypeAddToReadingList,
                               UIActivityTypePostToVimeo];

activityVC.excludedActivityTypes = excludeActivities;

[self presentViewController:activityVC animated:YES completion:nil];

为了更好的图片这里是截图:

使用默认应用:

使用Gmail:

我也尝试过不同的答案.但它们都不起作用.