Maybe it is not neccessary to get current page from the check buttons, but this will be done later. First I ' d like to tranfer the Scenes to singleton.
singleton seems a little complecated for this case, but I have to assure each scene is instantiated once.
Here has a bug, if the MainActivity is trashed, return from any other Activity would be set to SceneMain. But I don't see that would happen.
add a new activity for showing comments
ADD basic operation on TaskCommentActivity