Muzei is a live wallpaper application for Android that automatically refreshes the user's home and lock screen with artwork on a daily schedule. The system is built around a well-designed plugin architecture (muzei-api) that allows artwork to be sourced from curated feeds, the user's local photo gallery, single images, or third-party providers. The Android client features a custom OpenGL rendering engine (GLWallpaperService) for smooth transitions and visual effects like blur, dim, and greyscale overlays. A companion Android Wear app syncs the current wallpaper to smartwatch complications. The project also includes a web backend (Google App Engine, Python 2.7) that serves the curated artwork feed, manages an archive of past wallpapers, and provides an admin interface for scheduling. While the Android codebase is actively maintained and demonstrates strong engineering practices with several reusable components (e.g., cloud storage library, SVG path parser, GPU blur renderer), the web backend shows significant technical drift, relying on an EOL Python runtime and outdated JavaScript dependencies. The lack of visible unit tests is a notable gap for an application of this complexity.
PhotoEditor is an Android library (published on Maven Central) that provides a comprehensive image editing SDK. It allows users to draw on images with customizable brushes and shapes (line, oval, rectangle, arrow), apply filter effects via Android's deprecated MediaEffect API, add and edit text with rich styling (color, font, shadow, border), insert emoji and stickers, and perform pinch-to-scale/rotate gestures on added elements. The library is built around a `PhotoEditorView` custom RelativeLayout that composes an ImageView, a DrawingView (custom canvas for brush/shape rendering), and an ImageFilterView (GLSurfaceView for filters). The architecture employs several design patterns: Builder (PhotoEditor, ShapeBuilder, TextStyleBuilder, SaveSettings), Composite (Graphic interface with Text, Sticker, Emoji implementations), Strategy (Shape interface with concrete shapes), and Listener (OnPhotoEditorListener, BrushViewChangeListener). The sample app demonstrates all features. The library has a robust undo/redo system managed by GraphicManager and PhotoEditorViewState. While the core functionality is solid, the filter implementation relies on deprecated Android APIs (android.media.effect), which is a known limitation and source of issues. The codebase is well-structured with unit and instrumentation tests, CI/CD pipelines, and proper Kotlin coroutines for async saving.
Chocola is an offline music player for Android built with Kotlin and Jetpack Compose. It provides a full-featured music experience: library browsing by albums, artists, playlists, and folders; playback with equalizer, speed/pitch control, sleep timer, and shuffle/repeat modes; synced lyrics display and editing; metadata editing; Android Auto support; and home screen widgets. The app uses Material 3 design with a distinctive 'cute' theme, custom navigation, and extensive localization. The architecture follows a typical Android MVVM pattern with Room for playlist persistence, DataStore for preferences, ExoPlayer/Media3 for playback, and Koin for dependency injection. It scans local media via MediaStore and SAF, applies configurable filters (minimum duration, hidden tracks, whitelisted folders), and uses TagLib for metadata editing. While the codebase is well-organized and demonstrates solid Android engineering, it relies heavily on experimental Compose APIs and a custom navigation library, which introduces some technical drift risk. Overall, it's a mature, actively maintained open-source project suitable for reuse of specific UI components and data-layer patterns.
Aerial Views is an Android TV screensaver (DreamService) that plays aerial videos and photos from multiple sources—Apple, Amazon, community feeds, local storage, Samba, WebDAV, Immich, Nextcloud Memories, and custom feeds. It provides a rich overlay system (clock, date, weather, metadata, now-playing, countdown, message API) and supports hardware vendor integrations (Projectivy, Philips TVs). The architecture follows a provider pattern with a central ScreenController orchestrating playback, overlays, and services. The codebase is actively maintained with extensive internationalization, unit tests, and CI/CD. While the provider abstractions are clean and extendable, the ScreenController is large and tightly coupled, and the app has moderate technical drift (deprecated APIs, unusual compileSdk 37). Overall it's a well-engineered, feature-complete application for its niche.
Spam Call Blocker is an Android application written in Kotlin that blocks unwanted incoming calls using a combination of local blocklists, pattern matching, and real-time checks against multiple online phone reputation services (UnknownPhone, Tellows, Truecaller, and regional directories). It registers a call screening service to intercept calls, evaluates them against user-defined rules and external APIs, and can block, mute, or answer-and-hangup spam calls. The app provides a full settings UI for managing blocked/whitelisted numbers, pattern-based blocking, API toggles, and export/import of configuration. It also includes a donation screen and automatic update checking via GitHub releases. The codebase is well-structured with clear separation of concerns, uses Kotlin coroutines for concurrent API checks, and supports multiple languages.
SimpMusic is a production-grade Kotlin Multiplatform music player for Android and desktop (JVM) that streams from YouTube Music's undocumented backend. The codebase is organized around a shared Compose Multiplatform UI module (composeApp), Android entry points (androidApp), a desktop entry point (desktopApp), and optional feature modules for Google Cast, Last.fm scrobbling, and crash reporting. A separately referenced core submodule supplies domain and media-service logic. Internally it uses MVVM with Koin dependency injection, Repository interfaces backed by Room entities and DataStore, StateFlow-based ViewModels, and a large custom Compose component library covering home feed, library management, playlist sync, fullscreen player, lyrics, equalizer, podcasts, Android home-screen widgets, and a desktop mini-player. The app is shipped as a packaged consumer application with Play Store metadata, GitHub Actions, fastlane changelogs, and build variants that swap real integrations for empty stubs in FOSS builds.
FlorisBoard is a free and open-source Android keyboard (IME) application written in Kotlin with Jetpack Compose. In production it functions as a fully-featured soft keyboard service (FlorisImeService extends InputMethodService) with clipboard history management (Room-backed), emoji input with search and history, multi-language keyboard layouts (50+ locale JSON layouts), a custom extensions system for themes/keyboards/language packs, and a custom stylesheet-based theming engine called Snygg that powers all IME UI styling. The app also includes a settings activity (FlorisAppActivity) with ~30 configuration screens, a spell-checker service, backup/restore infrastructure, incognito mode, and a native Rust/JNI library scaffold for performance-critical work. The architecture is a multi-module Gradle build (:app, :lib:android, :lib:compose, :lib:kotlin, :lib:native, :lib:snygg) with a clear separation between the Android-specific app layer and reusable common KMP libraries.
This repository is an Android application that bridges device events (SMS, MMS, missed calls, battery changes, app notifications) to a Telegram bot for monitoring and remote control. It uses the Telegram Bot API to forward events and long-polls for incoming commands to send SMS, USSD, list/read/delete SMS, fetch logcat, and more. The architecture is a monolith with multiple background services, broadcast receivers, and job scheduler jobs, all within a single Android app. It uses MMKV for key-value storage, OkHttp for HTTP, Gson for serialization, and libsodium for encryption. The codebase is well-structured with reusable utility classes (e.g., custom Mustache template engine, Telegram API wrapper, encryption helpers) and has unit tests for several components. It supports multi-language, QR code configuration import, and carbon-copy forwarding to external services via HAR format.
Animite is an unofficial Android client for AniList (with partial MyAnimeList support) for tracking anime and manga. The application is built with a modern Android stack: Kotlin, Jetpack Compose, Material3, Apollo Kotlin (GraphQL), Ktor (REST), DataStore, Hilt, and Coil. It features a multi-module architecture with clear separation of concerns: API layers, core UI components, navigation, and feature modules (explore, profile, media, settings, social, anime, manga, banner). The app supports browsing, searching, filtering, detailed media pages with dynamic theming (time-of-day based banner), user profile management, and list editing with drag-and-drop reordering. The codebase demonstrates strong modularity and reusable UI patterns, though it relies heavily on experimental Compose APIs and has a few code quality concerns (e.g., hardcoded credentials, large screen files, alpha version instability).
CloudStream is an Android media aggregation application that streams and downloads movies, TV series, and anime via a plugin-based provider system. The app has no built-in content; all media sources are provided by community extensions implementing `MainAPI` and `ExtractorApi` interfaces. The architecture comprises a Kotlin Multiplatform library defining plugin APIs and an Android app with ExoPlayer/Media3 playback, download manager, sync with tracking services (MAL, AniList, Kitsu, Simkl, Trakt), multi-source subtitle fetching, Chromecast support, and adaptive phone/TV UI. Content acquisition relies on web scraping: over 100 built-in extractors parse video hosting sites, often using JavaScript deobfuscation (via a custom JS interpreter) and AES decryption. The plugin system supports repository-based distribution, versioning, and binary compatibility checks. While the codebase is actively maintained and demonstrates good engineering practices (MVVM, coroutines, custom adapters), many extractors are brittle due to external site dependencies, and some modules exhibit tight coupling and deprecated API usage.
WanAndroid is a polished, feature-rich Android client for the WanAndroid platform (wanandroid.com), a Chinese community for Android developers. The application provides comprehensive browsing of articles, projects, WeChat articles, knowledge trees, navigation, Q&A, book tutorials, and daily news aggregation from multiple Chinese sources. It implements a classic MVP architecture with a modular project structure (app, basic/core, basic/ui, basic/utils, basic/l10n, component/ad). Key entry points include SplashActivity and MainActivity (hosting a bottom-tab fragment container). The system heavily leverages OkHttp/RxHttp for network requests to the WanAndroid REST API, DiskLruCache for offline caching, Room for local persistence (read-later and read-history), and EventBus for cross-component events. Beyond vanilla browsing, it features a custom WebView subsystem (WebInstance, WebContainer) with resource interception, offline HTML/ CSS caching, a reading mode using readability4j and Jsoup, and JavaScript injection for image clicks. It also includes text-to-speech (TTS) via Android TTS engine with AI-powered summarization, biometric quick login, QR code scanning, card/article sharing, a coin/ranking gamification system, and in-app updates. External dependencies include Google AdMob for ads, optional AI provider APIs (e.g., DeepSeek), and the WanAndroid server endpoints. The codebase is a mix of Java and Kotlin, with several reusable custom UI components like BottomDrawerLayout, ImagePreviewView, CollectView, and custom pull-to-refresh headers with Chinese poetry.
BatteryRecorder is an Android application for precise battery power recording and battery life prediction. It consists of a main app module with Jetpack Compose UI and a native server daemon that reads battery data directly from sysfs and dumpsys via JNI. The architecture follows a multi-module structure (app, server, shared) with AIDL-based IPC between the app and the privileged background server. The app provides real-time monitoring, historical charts, per-app and per-scenario battery endurance predictions, calibration settings, and export/import capabilities. It is a sophisticated tool aimed at power users and developers, but it relies on device-specific sysfs paths and hidden Android APIs, making it fragile across different devices and Android versions. The codebase demonstrates solid use of modern Android patterns (ViewModel, StateFlow, UseCase, Repository) and custom Compose components, though it lacks automated tests and has mixed-language documentation.
Firefly is a high-performance asynchronous networking framework for the JVM, written in Java and Kotlin. It provides a comprehensive set of I/O primitives including HTTP/1.1, HTTP/2, WebSocket (RFC 6455), TCP, and UDP, with both client and server implementations. The framework is designed around Kotlin coroutines and Java NIO2 (AIO), offering non-blocking, backpressure-aware streams and a router-based HTTP server with support for content negotiation, CORS, static file serving, and HTTP/2 upgrade. It also includes built-in SLF4J logging with XML configuration, a JSON serialization service, a WeChat enterprise bot module, and a JNI helper for native code integration. The codebase is modular (firefly-common, firefly-net, firefly-slf4j, firefly-serialization, firefly-wechat, firefly-example) and demonstrates deep protocol-level craftsmanship with custom HPACK, Huffman coding, and state-machine parsers. While primarily a library for building network services, it also serves as a reference implementation for protocol handling on the JVM.
This repository is a Kotlin/Java library providing Certificate Transparency (CT) verification for Android and JVM applications. It prevents man-in-the-middle attacks by validating TLS certificates against public CT logs. The library offers multiple integration approaches: Java Security Provider, OkHttp interceptors, TrustManager and HostnameVerifier wrappers for HttpURLConnection/Volley/WebView, and direct API usage. Key features include CT log list fetching and parsing, SCT verification, optional CRL-based certificate revocation checking, and configurable caching. The architecture is modular with a core library, Android-specific extensions, and a sample application demonstrating all integration methods. The code employs modern Kotlin idioms (coroutines, sealed classes, builder patterns) and maintains strong separation of concerns between network fetching, policy enforcement, chain cleaning, and verification logic.
An Android audio recording and playback application with two coexisting architectures: a legacy Java MVP system (V1) and a modern Kotlin Compose MVVM system (V2). The app supports recording in M4A/AAC, WAV, and 3GP formats with configurable sample rate, bitrate, channel count, and audio source. It features waveform visualization during recording and playback, file management (rename, bookmark, trash, import/export), broken-record recovery, and a customizable name-format builder. The V2 codebase uses Jetpack Compose, Hilt dependency injection, Room database, ExoPlayer, and coroutines, while V1 uses Android Views, SQLite, and manual DI. The dual-codebase design adds complexity and maintenance risk, but the V2 components are well-architected with a clean unidirectional data flow and reusable patterns for media handling and UI state management. The project has extensive localization (18 locales), fastlane metadata for Play Store, and a custom home-screen widget.
This repository is a Kotlin Multiplatform (KMP) library collection designed for rendering rich text and Markdown within Compose applications on Android and Desktop. It consists of several modular artifacts: `richtext-ui` (core UI composables), `richtext-markdown` (AST-based rendering), `richtext-commonmark` (CommonMark parser integration), and theme-specific wrappers (`richtext-ui-material`, `richtext-ui-material3`). The architecture relies on a custom Abstract Syntax Tree (AST) representation of Markdown content, which is traversed recursively to emit Compose composables. While the codebase demonstrates strong engineering practices, particularly in handling deep nesting and large documents, the README explicitly warns that the project is experimental, lacks tests, and has an unclear roadmap. This makes it suitable for prototyping or internal tools but potentially risky for production-critical applications without significant validation.
This is a privacy-focused Android application for scanning and generating QR codes and barcodes, developed by the SECUSO research group (Security, Usability, Society) at TU Darmstadt. The app uses the device camera to decode codes, supports image picker scanning, and provides a QR code generator for various content types (URL, text, email, phone, SMS, WiFi, vCard, MeCard, BizCard, geo-location, product, calendar, etc.). It emphasizes minimal permissions (only camera, no internet required for scanning) and includes phishing protection by highlighting domains and requiring user confirmation before opening links. The architecture follows standard Android patterns: Activities with ViewModel + LiveData, Room database for scan history, Repository pattern, and a navigation drawer for main sections (Scanner, Generator, History, Settings, Help, About). The codebase is a mix of Java and Kotlin, uses AndroidX, Material Design, ZXing for barcode decoding, and Glide for image loading. It also integrates a backup service via a git submodule (privacy-friendly-backup-api). The app is part of the Privacy Friendly Apps suite and is licensed under GPLv3.
Prog8 is a Kotlin/JVM compiler and language toolchain for retro 8-bit/16-bit platforms (C64, C128, CX16, PET32, Amiga, m68k). It compiles a high-level language to 6502/68000 assembly through a multi-stage pipeline: lexer/parser, AST construction, semantic analysis, intermediate representation, optimizer, code generation, and optional VM execution. The repository also includes an LSP server, a Gradle build with Kotest tests, CI workflows, and target-specific runtime libraries. It is primarily an application (compiler/CLI), not a data/research project.
AdAway is an open-source Android ad-blocking application that provides two methods for blocking ads: modifying the system hosts file (requires root) and a local VPN-based DNS filter. The app downloads and manages multiple hosts sources from URLs, parses them into a local Room database, and applies the blocklists either by writing to /etc/hosts or by intercepting DNS queries through a local VPN service. The VPN mode maps real DNS servers to fake addresses, forwards allowed queries, and returns blocked or redirected responses. The architecture follows MVVM with LiveData, ViewModel, and Room, and includes background workers for periodic updates. The app bundles a legacy native C library (tcpdump/libpcap) for packet capture, used for DNS logging. The codebase is actively maintained, with frequent commits and releases, but some native components are outdated and the VPN implementation may have compatibility issues on newer Android versions.
This repository is an educational resource focused on teaching the Gang of Four (GoF) design patterns through comprehensive explanations, code examples, and diagrams. It covers creational, structural, and behavioral patterns, with each pattern accompanied by detailed markdown documentation, visual diagrams, and runnable code samples in both Java and Kotlin. The project structure organizes content by pattern type, making it easy to locate and study specific patterns. The code examples demonstrate practical implementations of each pattern in context-specific scenarios, such as a banking system for the Command pattern, a notification system for the Decorator pattern, and a file system for the Composite pattern. While the build configuration defaults to running a Singleton demo, each pattern includes independent main functions or demo classes that can be executed separately. The repository also features automated workflows for building and deploying the documentation via GitHub Pages. Despite some maintenance challenges like duplicate documentation files (marked for removal in a future version) and the coexistence of Java and Kotlin examples, the project shows active maintenance through contribution guidelines, regular updates, and a clear migration path toward consolidating documentation. The examples are well-crafted, self-contained, and illustrate core object-oriented design principles effectively, making them valuable for both learning and reference purposes.