share Extension IOS 8: How do I remove share itself activity in share category?

Question

Please see the

As you see, It has a button is share Button. I want to remove it. I use share Extension to do share screen shot for my app:

• add target share Extension
• use UIActivityViewController to present.

I able to remove Mail Button, FaceBook button by using this:

[activityView setExcludedActivityTypes:@[UIActivityTypePostToFacebook,UIActivityTypeMail]];

but I can't remove the shareButton by the way. Can you help me?