Little Chef Timer
100% offline Android kitchen timer with exact alarms that fire even when the phone is locked, in Doze mode, or after the app has been killed by the system.
Last updated:
The Problem
Generic kitchen timers don't distinguish between preparations, lose the countdown if the system kills the app or the phone reboots, and their alarm can fail due to Android's Doze battery-saving mode.
The Solution
An offline app that stores custom recipes with an emoji, notes and an exact duration, and schedules the alarm with AlarmManager.setAlarmClock so it fires on time even with the screen locked or in Doze mode. The remaining time is derived from a persisted end timestamp, so it survives process death without drift, with no foreground service running in the background.
Key Learnings
- Drift-free countdown: remaining time is derived mathematically from a persisted end timestamp (endAtMillis) in SharedPreferences, instead of a counter that could be lost if the process dies.
- Exact alarms without invasive permissions: AlarmManager.setAlarmClock fires precisely even in Doze mode, without requesting SCHEDULE_EXACT_ALARM.
- Reactive UI without polling: a SharedPreferences.OnSharedPreferenceChangeListener wired to a Compose DisposableEffect updates the UI only when state changes, with no periodic disk reads.
- Per-sound notification channels: since a channel's sound is immutable once created, each chosen ringtone gets its own channel (alarm_<hash>), with older ones deleted.
Architecture Without Room or a Foreground Service
Little Chef Timer is a single-module app designed to consume zero battery while the timer is running:
- Simple persistence in
SharedPreferences: the recipe catalog is a short list, so it’s stored as validated JSON in preferences, avoiding the overhead of a relational schema and its migrations. - The system’s own alarm, not a custom service: the countdown is computed as
endAtMillis - now, andAlarmManagerhandles waking the device at the exact moment, with zero CPU cycles spent while the phone is idle. - Insistent notification: when it fires, a high-importance notification with
FLAG_INSISTENTloops the sound until the user taps Stop.
Personalization and Backup
- Custom recipes with emoji and notes: each preparation has a title, emoji, cooking notes, and an exact duration.
- Live theming and bilingual UI: a lilac/pink palette in Light, Dark, or System theme, with Spanish/English language switching without restarting the app.
- Backup without broad permissions: export and import recipes as JSON via the Storage Access Framework, without requesting general storage access.
Note: You can explore the source code and technical documentation directly in the GitHub repository.
This page is a high-level summary. The GitHub repository is the source of truth for each tool's current features. GitHub ↗