I built an open-source Android app that switches dark mode based on ambient light – Adaptive Theme

Lexip — Sat, 03 Jan 2026 11:56:10 +0000

Howdy and happy new year!

I wanted to share an open-source project of mine, that I’ve been working on in my free time:

Adaptive Theme

It automatically switches between Light and Dark mode using the ambient light sensor - not a fixed schedule. Therefore it optimizes readability, eye comfort, and maybe even battery life.

And it's free, ad-free, and open-source, just like it should be. :)

Play Store: play.google.com/store/apps/details?id=dev.lexip.hecate

GitHub Repo: github.com/xLexip/Adaptive-Theme

Battery Efficiency

To avoid the battery drain with constant sensor polling, the app is entirely passive.

I built an event-driven architecture that only checks the light sensor for a split second immediately after the screen turns on. Zero background polling and activity, since it only reacts to system broadcasts.

This event-driven architecture does only work on Android 14 and above. Below that, the sensors can't be properly read in the receiver.

Setup & Permissions

That's the biggest challenge: The app requires WRITE_SECURE_SETTINGS to change the system theme.

Unfortunately this can't be granted that easy and deters many users. So I've tried to make it as easy as possible and implemented a wizard-based setup flow to help grant this via one of multiple methods:

Web Tool (Recommended) – A browser-based setup tool to use with another device. No code or ADB installation required (WebADB). It's at lexip.dev/setup
Shizuku – If you have Shizuku installed and configured, you can grant the permission directly within the Adaptive Theme app.
Root – If your device is rooted, you can grant the permission with one tap inside the app.
Manual ADB – If you have ADB installed on your computer, you can run the ADB command manually.

Tech Stack & Architecture

UI: Jetpack Compose with Material 3 / Material You. I've tried to rebuild the system settings look in my app (stock/Pixel), hope you like it.
Architecture: MVVM with Single-Activity pattern.
Concurrency & Streams: Kotlin Coroutines and Flows for reactive state management.
Persistence: Jetpack DataStore for type-safe settings storage.

Build Flavors

I maintain two distinct build flavors to keep the core app FOSS-compliant:

Play Store: Does includes Firebase (proprietary, crash logs etc.).

FOSS (GitHub Releases, etc.): Completely clean build with no proprietary blobs or trackers at all.

I’m curious to hear your thoughts and opinions!