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// Project case study

CodeDroid

A pocket development environment for Android where Python and JavaScript run on-device, other languages can use a cloud runner, and the editor remains usable offline.

Download APK GitHub
Role
Creator & developer
Duration
Jun 2026
Stack
KotlinJetpack ComposeMaterial 3CodeMirrorChaquopyRhinoPiston API

The Problem

Mobile code editors stop at syntax highlighting — you can't actually run anything.

The Approach

Offline CodeMirror editor plus on-device Python (Chaquopy) and JavaScript (Rhino), with a cloud runner for other languages.

The Outcome

An installable APK that edits and runs code in 18 languages, with a terminal, packages and live HTML/CSS preview.

Product film — CodeDroidPlays when in view

Who it's for

Students, mobile learners, and developers who want to experiment with code from an Android device instead of being limited to a desktop setup.

The challenge

Mobile editors often stop at syntax highlighting. CodeDroid treats the phone as a real development surface, so editing, execution, file management, terminal feedback, and offline use need to work together.

What I built

The product combines an offline CodeMirror editor with syntax highlighting for 18 languages, on-device Python through Chaquopy, JavaScript through Rhino, cloud execution through Piston for other languages, an integrated terminal, runtime package installation, persistent tabs, autocomplete, Vim keybindings, and live HTML/CSS preview.

Why it matters

The project lowers the barrier between learning and running code. A student can move from a small experiment to visible output on the same device, while the offline editor and on-device runtimes keep the core experience useful without a constant connection.

How it works

  1. 01Open or create a file in the offline editor and choose a language.
  2. 02Run Python or JavaScript locally, or send supported languages through the cloud runner.
  3. 03Read terminal output, provide stdin, and iterate without leaving the app.
  4. 04Use tabs, search, autocomplete, packages, and live HTML/CSS preview to move from experiment to working result.

Scope note

The public repository shows a CodeDroid v1.1 release and provides the latest APK through GitHub Releases. The portfolio links to that release rather than claiming a separate web demo.

System Architecture

  1. 01

    Editor

    CodeMirror in WebView

  2. 02

    App shell

    Kotlin · Jetpack Compose

  3. 03

    On-device runtimes

    Chaquopy · Rhino

  4. 04

    Cloud runner

    Piston API

  • Kotlin, Jetpack Compose, and Material 3 for the Android interface.
  • CodeMirror 5 bundled in a WebView for offline editing.
  • Chaquopy for Python, Rhino for JavaScript, and Piston for additional languages.
  • Storage Access Framework and DataStore for files and persistent preferences.

// Learnings

What this project taught me

  • 01Bundling the editor offline matters more than adding features.
  • 02Running untrusted code needs clear separation between runtimes.
  • 03Storage Access Framework makes file handling predictable on modern Android.
View source on GitHub Download the latest APK

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