Milline mehhanism on parem UI oleku salvestamiseks: ViewModel või SaveInstanceState, ja kuidas nad erinevad?

ViewModel and SaveInstanceState serve to preserve UI state, but they work differently and are intended for different tasks.

• ViewModel stores data in memory during configuration changes (e.g., screen rotation). It lives as long as the Activity or Fragment, and is not destroyed when the UI is recreated. It is suitable for storing large amounts of data and business logic.

• SaveInstanceState is a mechanism for saving small data in a Bundle, which is preserved when the system destroys the Activity (e.g., due to low memory). Data from SaveInstanceState is restored when the Activity is recreated.

Which is better to use?

• For saving UI state that should survive screen rotation, it is better to use ViewModel.
• For saving critical data that needs to be restored after the app is fully destroyed by the system, SaveInstanceState is used.

They are often combined: ViewModel for main logic and data, SaveInstanceState for small primitive data that needs quick restoration.