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Lifecycle, process, Binder, and components

Core questions​

Activity versus process lifetime: an Activity instance can be recreated for configuration; the process can die without lifecycle callbacks while app is backgrounded. Durable data belongs in storage/server, screen state in ViewModel/SavedStateHandle according to size/reconstructability, and Views/Compose render current state.

ViewModel guarantee: survives configuration within its owner scope; it does not survive process death and should not hold Views/shorter-lived Context.

Service: component for work needing service semantics, not a background thread. Current background/foreground restrictions, user visibility and work type determine legality. WorkManager handles deferrable guaranteed work; alarms handle justified time-based wake; none are interchangeable.

BroadcastReceiver: short-lived entry point; return quickly and hand durable asynchronous work to an allowed mechanism. Export/permission/input validation are security boundaries.

ContentProvider: structured cross-process data/initialization component; URI grants and exported permissions matter. Avoid accidental startup work.

Binder/IPС answer​

Binder is Android's kernel-mediated IPC/RPC mechanism. Calls cross process/thread pools; arguments are marshalled and transaction size/liveness/death matter. Never assume remote object is local, cheap or alive.

client proxy -> Binder driver -> server Binder thread
             <- result/exception <-

Avoid main-thread IPC, large payloads and lock-held calls. Handle RemoteException, binder death, reconnection, caller identity and server-side authorization. AIDL gives typed contracts; Messenger serializes messages; bound services manage connection lifecycle.

Scenario drills​

  1. Upload must continue after swipe/process death/reboot: define durable intent, WorkManager constraints/idempotency and server reconciliation.
  2. Deep link opens logged-out checkout: validate link, save safe return intent, authenticate, re-authorize server-side and restore navigation.
  3. Bound media service dies: UI shows disconnected, reconnects without duplicate commands and reloads authoritative playback state.

Common weak answers​

  • ❌ “onDestroy always saves data.”
  • ✅ process death may provide no callback; persist before correctness depends on it.
  • ❌ “Service runs in background.”
  • ✅ component lifecycle and execution/thread are separate.