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Process death lifecycle

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Process Death Lifecycle Deep Dive

Overview

Android can kill app processes under memory pressure. Robust apps restore state correctly when process is recreated.

What Survives and What Doesn't

Lost on Process Death

  • In-memory objects
  • ViewModel instances
  • Ongoing in-process jobs

Can Be Restored

  • savedInstanceState UI state
  • Persisted data from Room/files/preferences

Recovery Pattern

  1. Save lightweight UI state in onSaveInstanceState.
  2. Keep source of truth in persistent storage.
  3. Rehydrate screen state from repository on recreation.
override fun onSaveInstanceState(outState: Bundle) {
    super.onSaveInstanceState(outState)
    outState.putInt("scroll", recyclerView.computeVerticalScrollOffset())
}

Architecture Guidance

  • UI state: Bundle + SavedStateHandle.
  • Durable state: Room/DataStore/network cache.
  • Avoid relying only on ViewModel for critical data.

Interview Traps

  • "ViewModel survives process death" -> false.
  • Assuming onDestroy() always runs before death -> false.

Key Takeaways

  • Design for process death from day one.
  • Persist essentials and restore deterministically.