In iOS 8, UIActivityViewController is still an API that only provides custom functions, but not custom UI. You can’t change the way it looks. The only part of the visual style you can change is the icon of your custom UIActivity subclasses. (ref)
This is how Apple implements this, and it cannot be changed as of 8.3. If you really want to avoid the extra row and the “More” button, you can implement a UIActivityViewController replacement. Here are a couple that have been recently maintained:
OvershareKit
URBNShareKit
References:
- UIActivityViewController Hide More from Actions
- UIActivityViewController on iOS 8 show “more” button with custom activities
- Can I exclude “More” Button in UIActivityViewController?
- http://getnotebox.com/developer/uiactivityviewcontroller-ios-8/