Retaining Fragment instance (no configuration change) with ViewPager

Question

As the title suggests, I want to retain my fragments. I have enforced my app orientation to always be in landscape mode in the manifest file so that there will be no rotations.

I have read: Understanding Fragment's setRetainInstance(boolean) and Why use Fragment#setRetainInstance(boolean)? However, I am not sure if they apply to my situation.

My project consists of a ViewPager with swipe tabs. How can I ensure that the fragments used in the ViewPager are the same ones as created when the MainActivity first starts? Would I use the same tagging method and findfragment by tag?

Additionally, where would it be best to check for the tagged fragment, else create a new fragment?

Just a side question related to ViewPager: what can I do to immediately create all fragments used in the ViewPager when the mainactivity is started, rather than to wait for a swipe event to occur?

Answer 1

To answer your last question view pager will by default create the fragments around the current fragment so you don't need to worry about that part. What I would recommend is let the view pager manage your fragments for you rather changing the behaviour since you might face performance issues.

SetRetainInstance simply keeps the instance of your fragment when its detached so it's up to you to assess whether you need to use it or not.. is there anything you want to maintain about that fragment? if not then do not use it, free your memory as much as possible.

For the last question, why do you want the same fragments created from the first time to be retained ? all the time? if you NEED to do that then rethink your structuring. gracefully recreate your fragments and maybe have some caching of your data on another layer if that is what you are worried about.