Interview guides / android

Activity leak + token logs: Android Interview Question

Activity leak + token logs interview question with a clear example answer for Android engineers. Practice with AceMobileInterview.

This is a common Android interview topic: Activity leak + token logs.

Below is a concise answer you can adapt in a real interview, then go deeper in the full AceMobileInterview track.

1. 1.Profile visits leak the Activity; Logcat prints the session token. Fix leaks and unsafe logging (≈30–45 min).

   ## Scenario Leaky Profile screen + secret in logs. ## How to investigate - LeakCanary or Profiler heap dump - Confirm Activity instance count after repeat visits - Grep `Log.` for token ## Planted bug 1: Static Activity reference **Symptom:** Activity retained after finish **Root cause:** `companion object { var host: Activity? }` set in `onCreate` never cleared **Fix:** Remove static; use application context only where safe; clear in `onDestroy` ## Planted bug 2: Uncancelled coroutine / listener **Symptom:** Callback touches dead UI **Root cause:** `GlobalScope.launch` or listener registered without removal **Fix:** `lifecycleScope` / `viewModelScope`; unregister listeners ## Planted bug 3: Logging secrets **Symptom:** Token in Logcat **Root cause:** `Log.d("Auth", token)` **Fix:** Delete; redact if absolutely needed ## Optimization tips - Treat Logcat as public on shared devices / bug reports - Prefer ViewModel for async that outlives rotation ## What to say in the interview - How you confirmed the leak root in the dump - Why `GlobalScope` is a red flag