ViewModels: Persistence, onSaveInstanceState(), Restoring UI State

ViewModels are designed to hold and manage UI-related data in a life-cycle conscious way.

Transcript

1. Versio 1.0 ViewModels: Persistence, onSaveInstanceState(), Restoring UI State
2. Profile I am Nsikak Thompson I build for Android A community Advocate Technical Writer @medium/droidplate @thompson_nsikak
3. TOC Overview Problems to solve Project objective Market trends Trend analysis Target audience Proposed solution Process Deliverables Vision Team Next Billion Users
4. Overview ViewModels are designed to hold and manage UI-related data in a life-cycle conscious way.
5. Do ViewModels persist my data? No, Persist as Normal
6. Are ViewModels a replacement for onSaveInstanceState? No, There are related
7. How do I use ViewModels to save and restore UI state efficiently? You use a combination of ViewModels, onSaveInstanceState() and local persistence.
8. Do ViewModels persist my data? ViewModels hold transient data used in the UI but they don’t persist data. Once the associated UI Controller (fragment/activity) is destroyed or the process is stopped,
9. The MVVM pattern
10. The lifecycle of a ViewModel The ViewModel remains in memory until the Lifecycle it's scoped to goes away permanently:
11. Stop Detach Activity Fragment
13. App killed - Low memory - Shut down due to resource constraints - device runs out of battery
14. Long Live Data ViewModel and Local persistence
15. Avoid Loading Screens
16. Local Persistence storing all data you don’t want to lose if you open and close the activity
17. Local Persistance
19. ViewModel vs SaveInstanceState onSaveInstanceState(): This callback is meant to retain a small amount of UI related data in two situations: 1. The app’s process is stopped when it’s in the background 2. Configuration Changes
20. ViewModel vs SaveInstanceState Persist Small amount of data with Saveinstancestate Such as search queries
21. ViewModel vs SaveInstanceState
22. ViewModel vs SaveInstanceState
23. Recap • Local persistence is used for storing all data you don’t want to lose if you open and close the activity. • ViewModels are used for storing all the data needed to display the associated UI Controller. • onSaveInstanceState is used for storing a small amount of data needed to easily reload activity state if the UI Controller is stopped and recreated by the system. E.g search query
24. Resources https://developer.android.com/topic/libraries/a rchitecture/guide.html https://goo.gl/o6RX9J
25. Thank you.