Nested Fragments

A summary of challenges we faced while creating a truly scalable dynamic home page of the new zomato app.
The talk takes the user through the journey of the problem we had at our hands, the way we looked at it, the challenges we faced and finally what we ended up creating.

Android Challenges(Topics) that this talk covers
1. FragmentPagerAdapter
2. FragmentStatePagerAdapter
3. ViewStubs

Transcript

1. Series of (Un)Fortunate events Sajal & Prateek Zomato
2. New Zomato App • Feature outline ◦ Bottom Navigation Tabs ◦ Each tab could/ could not host nested content. • Dynamic Content ◦ Both bottom tabs and the nested content can be vastly different dependent on plethora of parameters like city / user / product launches / promotions etc.
3. Dissecting the problem • Defining the basic premise of parent child content holders • Possible re-use of “content” holder ◦ Fragments .. Nested ? ◦ PagerAdapter ? -- Choices?
4. FragmentPagerAdapter - The issue Fragment A,B,C Fragment B,C,D notifyDataSetChanged() FragmentManager : Fragments A,B,C,D
5. FragmentPagerAdapter
6. What we need • Destruction of fragments when not in use • Fragment state management • Invalidate reused fragments
7. FragmentPagerAdapter
8. FragmentPagerAdapter
9. FragmentStatePagerAdapter
10. FragmentStatePagerAdapter
11. FragmentStatePagerAdapter - The issue Fragment A,B,C Fragment B,C,D Restoring State by position
12. FragmentStatePagerAdapter
13. FragmentPagerAdapter - The issue Fragment A,B,C Fragment B,C,D notifyDataSetChanged() B and C are unaware of the change. Invalidation may/ may not be required.
14. ViewPager - Invalidate items
16. Need to set ViewPager offset • Bad UX. • Multiple calls to server on navigating through app.
17. ViewPager offset = list.size() Creation and inflation of multiple NESTED FRAGMENTS!!! on every notifyDataSetChanged()
18. ViewStubs ftw * A ViewStub is an invisible, zero-sized View that can be used to lazily inflate layout resources at runtime. * abstract fun getLayoutResourceId(): Int
19. Lazy Fragments - To the rescue
20. Lazy Fragments - To the rescue
21. Magic Sauce
22. Nested Lazy Inflation onCreateView() of Parent fragment onViewInflated() of Parent fragment Creation of ViewPager of Parent fragment onCreateView() of child fragments within offset onViewInflated() of SELECTED FRAGMENT only and so on..
23. That’s pretty much it.. @SajalGupta94 @_prtks