Question 1: all code of these 5 pages should be written at Main Activity? Is there any way to use other activities, in order to be more maintainable.
Question 2: if i fetch all data simultaneously (timeline, search, notifications, profile), i think it will cause ootd memory problem.
What is best solution about this kind of applications;
It depends on all kinds of things. However unless you are showing very large images or lists then it is unlikely that you will have any memory problem.