Milos Fec, Developer in Prague, Czech Republic
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Milos Fec

Verified Expert  in Engineering

Jetpack Compose Developer

Prague, Czech Republic

Toptal member since January 28, 2016

Expertise
APIAndroid SDKAndroidREST APIJavaCGitC++JiraKotlinEmbedded Systems EngineeringLinuxVisual Basic
Bio

Milos is passionate about Android, and his work experience reflects that. He has built Java applications, creating native C/C++ libraries and Java wrapper classes using JNI and C# .NET using MonoDroid. He has worked as the team lead and developed a modified Android OS for a payment terminal with a high focus on security, including Linux hardening. Milos has also introduced new system apps, services, and Android framework modifications.

Portfolio

A prominent FinTech company
Android, Android HAL, Linux Kernel, Android Kernel, C++, C, Camera API...
Industry Leader in Waste Management Services
Android, WorkManager API, REST APIs, Observer Pattern, Room, Kotlin, Java...
Freelance Client
Compose Multiplatform, Bluetooth Low Energy (LE), iOS, Android, Xcode...

Experience

  • Android SDK - 14 years
  • Java - 12 years
  • C - 8 years
  • C++ - 8 years
  • JNI - 5 years
  • Android NDK - 5 years
  • Kotlin - 5 years
  • Jetpack Compose - 3 years

Availability

Full-time

Preferred Environment

Git, Android Studio, Linux, MacOS

The most amazing...

...work I've done was the Android OS development for an unique payment terminal called Aevi Albert.

Work Experience

Senior Android Developer for a fraud reproduction POC

2025 - 2025
A prominent FinTech company
  • Analyzed potential methods for injecting a multimedia stream into the Android system to emulate a hardware camera input.
  • Developed custom Android builds for various devices to comprehensively test potential solutions, including camera driver and HAL modifications, kernel changes, Android framework overlays, and more.
  • Leveraged Video4Linux2 to modify camera streams without requiring system modifications.
Technologies: Android, Android HAL, Linux Kernel, Android Kernel, C++, C, Camera API, Device Drivers, AOSP, FFmpeg, GStreamer, JNI, Android Rooting, Android Studio

Senior Android Developer

2022 - 2025
Industry Leader in Waste Management Services
  • Refactored Android app to MVVM, Kotlin, Coroutines, Dependency injection (Hilt), Jetpack Compose, Unit testing.
  • Implemented Android Workers for handling data synchronization.
  • Fine-tuned the integration of Bluetooth PTT microphones, addressing performance and stability issues and ensuring seamless operation.
  • Added support for external USB cameras (UVC), with special attention to edge cases such as camera disconnection/reconnection and light adaptation, ensuring that automated photo capture consistently produces high-quality images.
  • Developed in-app video calling functionality using Jitsi, incorporating local customizations and configuring the development environment with Docker Compose, port forwarding, and firewall rules.
  • Implemented AI-powered camera vision functionality using LiteRT, including the creation of a custom dataset (combined with a filtered and modified COCO dataset), training and evaluation of models trained using diverse techniques and tools.
Technologies: Android, WorkManager API, REST APIs, Observer Pattern, Room, Kotlin, Java, Jetpack Compose, Model View ViewModel (MVVM), Test-driven Development (TDD), GPS, Location Services and Maps, Coroutines, Hilt, Camera API, USB, Bluetooth, Unit Testing, UI Testing, Google Maps, TensorFlow, TensorFlow Lite, You Only Look Once (YOLO), Ultralytics, Python, Docker, Docker Compose, Jitsi, Roboflow, UVC, Android Studio

Multiplatform App Developer

2024 - 2024
Freelance Client
  • Created multi-platform mobile app using Compose Multiplatform for Android and iOS.
  • Reverse-engineered and analyzed Bluetooth LE communication with custom hardware by supplementing incomplete / inaccurate documentation, and implemented robust solutions for both Android and iOS platforms.
  • Developed an adaptive user interface optimized for multiple platforms and a wide range of screen sizes, ensuring a seamless experience from small phones to large tablets.
  • Resolved various cross-platform differences, including app permissions handling, PDF content display, and the consistency of UI elements and styles.
Technologies: Compose Multiplatform, Bluetooth Low Energy (LE), iOS, Android, Xcode, Android Studio

Android Developer

2021 - 2022
Blue River Technology
  • Worked with VLC, FFmpeg, and GStreamer to deliver a highly optimized solution for displaying video streams over a local network, with focus on minimal latency.
  • Implemented SSH and SCP to capture and obtain pictures from a remote server.
  • Set up multiple Docker containers to accelerate testing during development, leveraging Docker Compose to run custom debugging tools (originally developed for Windows) on other platforms, including support for GUI.
  • Used Python and OpenCV to replicate the image manipulation performed in the production solution, enabling the development and testing of the Android app in an environment similar to real-world use cases.
Technologies: Android, Kotlin, JavaScript, Architecture, Java, Python, Docker, Docker Compose, FFmpeg, GStreamer, libVLC, Firebase, Android Studio

External Consultant | Firmware Developer

2021 - 2021
Prusa
  • Provided consultancy on development standards, workflow, and processes to provide high-quality and maintainable solutions.
  • Designed, documented, and implemented platform-specific safe ways to update the bootloader.
  • Implemented POSIX filesystem calls for small ARM Embedded platform, including FAT and LittleFS filesystem mounting.
  • Prepared Python framework for automatic firmware tests using QEMU emulator.
Technologies: C, C++, ARM Embedded, FreeRTOS, Bootloaders, Embedded Development, Software Design, Embedded C++, Embedded Systems, Low-level Programming, Embedded C, Embedded Linux

External Consultant | System Developer

2020 - 2021
2N
  • Identified and fixed critical bugs of Android devices (Kernel, Linux binaries, and system services), preparing tools and custom builds for monitoring specific issues.
  • Cooperated on the development of a new Android device (operating system development, architecture, and security).
  • Consulted regarding Android API, system services, and optimizations.
Technologies: Jenkins, Jira, Gerrit, Git, Linux Kernel, Java, C++, C, Android SDK, Android NDK, Embedded Development, Software Design, Embedded C++, Embedded Systems, Low-level Programming, Kotlin, Android HAL, Embedded C, Embedded Linux, Android Emulators, Observer Pattern, Agile Software Development, SQL, JNI, FFmpeg, GStreamer, Android Rooting, Android Studio

Head of Mobile Platforms

2018 - 2020
2N
  • Helped prepare an Android device for release by fixing several critical bugs in the Bootloaders, Kernel, Android recovery, and framework.
  • Introduced quality standards on coding style, commit style, and workflow.
  • Refactored legacy solutions to use Android and Linux standards, improving stability and maintainability.
  • Fixed long-term issues of older Android devices. Used Android framework and apps, Kernel drivers, and Native Daemon.
  • Closely cooperated on designing a new product for both software and hardware.
  • Cooperated with multiple departments and suppliers on software, hardware, manufacturing, and quality control.
  • Identified security issues before implementation and designed solution improvements to prevent risks.
  • Led a team of five developers working on the system and Android apps.
Technologies: GitLab CI/CD, GitLab, Jenkins, Gerrit, Confluence, Jira, Git, C++, C, Java, Android API, Android NDK, Android SDK, Embedded Development, Software Design, Embedded C++, Embedded Systems, Low-level Programming, Kotlin, AOSP, Android HAL, Embedded C, Embedded Linux, Android Emulators, Observer Pattern, Room, REST APIs, Scrum, Agile Software Development, SQL, JNI, FFmpeg, GStreamer, Android Rooting, Android Studio

Developer | Owner | CEO

2009 - 2018
Limeas
  • Designed and developed J2ME applications according to the client's specifications.
  • Consulted companies that were creating Android multimedia applications (using DRM).
  • Developed Android apps that implement ad services, Google Analytics, and Play Store In-app billing.
  • Developed an Android service running in a separate process for a large bitmap manipulation (preventing memory fragmentation in the app's main process).
  • Created an Android library providing extended functionality (new Views and ViewGroups, Drawables, media manipulation, and other tools).
  • Gained experience with miscellaneous Android libraries and tools (Android support libraries, third-party libraries, a DDMS/Device Monitor, and MemoryAnalyzer).
  • Hired and coached several developers working on Android apps, Cloud services, and website.
Technologies: Git, Android, C#, C, C++, J2ME, Java, Software Design, Bluetooth, Low-level Programming, Kotlin, Observer Pattern, Room, WorkManager API, REST APIs, SQL, Eclipse Memory Analyzer, Eclipse IDE, JNI, Model View Presenter (MVP), Android TV, OkHttp, Digital Rights Management (DRM), NetBeans, Android Studio

Android Developer

2017 - 2017
Techona
  • Integrated WebView with optimizations (pre-caching of resources).
  • Implemented an advanced filter and search engine.
  • Wrote automated UI tests (Espresso and Appium).
  • Automated the build process for many build variants.
  • Created the architecture for the project and refactored it (MVP pattern).
Technologies: Python, Appium, Espresso, Java, Software Design, Observer Pattern, Room, REST APIs, Scrum, Agile Software Development, Model View Presenter (MVP), OkHttp, Dagger 2, Android Studio

Android Developer

2016 - 2016
Datasys
  • Automated UI tests (Appium).
  • Integrated communication with the payment terminal.
  • Integrated printing using thermal printer.
  • Created custom printing library with hi quality bitmap generation.
  • Refactored XML layouts and styles for clean, reusable, and maintainable code.
  • Implemented synchronization of local database with the server.
Technologies: Appium, Java, Bluetooth, Observer Pattern, REST APIs, Scrum, Agile Software Development, SQL, Model View Presenter (MVP), OkHttp, Dagger 2, Android Studio

Android Team Lead

2016 - 2016
Chess.com
  • Analyzed and refactored code to use the MVP pattern.
  • Created reusable views and components using a common app style.
  • Added new features, focused on long term stability and maintainability.
  • Cleaned up Git branches, specified and applied Git workflow.
  • Set up processes for issues tracking, Jira workflow, app versioning, and release planning.
  • Wrote documents about project structure, code style, commit style and other standards.
  • Set up quality assurance and release processes for Android application.
  • Led team of five Android developers, all working remotely.
Technologies: Fabric, Amplitude, Dagger, Android, Java, Software Design, REST APIs, Agile Software Development, Model View Presenter (MVP), Android Studio

SW Architect | Team Leader

2013 - 2015
Wincor Nixdorf
  • Optimized an app UI for better HW acceleration performance.
  • Created an Android library for communication with an asynchronous dial-up USB modem connecting to a banking server using an asynchronous dial-up modem.
  • Cooperated with an external company providing security features, implemented Linux hardening on an Android 4.0 operating system, modified permissions to fulfill requirements, and gained PCI certification.
  • Introduced new system apps and services to maintain security features above the scope of the regular Android operating system.
  • Modified an Android framework, specifically the UI and back-end functionality.
  • Led a team of seven developers working on the Android operating system.
Technologies: C, C++, Java, Software Design, Embedded Systems, Low-level Programming, AOSP, Gerrit, Embedded Linux, Android HAL, REST APIs, Scrum, Agile Software Development, SQL, Eclipse Memory Analyzer, Eclipse IDE, JNI, OkHttp, Android Rooting, Android Studio

Mobile Developer

2008 - 2013
Resco.net
  • Created Windows Mobile applications (C/C++).
  • Built a library for communication with Bluetooth headsets (AVRCP).
  • Developed Android applications (Java).
  • Developed an Android local proxy server for internet radio streaming with the added functionality of reading meta tags (song info) and recording stream simultaneously with playback.
  • Worked on a multi-platform project Mobile CRM (Windows Mobile, Windows Phone, Android, iOS) using MonoDroid.
  • Constructed native libraries (C/C++) with corresponding Java libraries (using JNI), integrated Java libraries into C# MonoDroid project.
Technologies: MonoDroid, .NET, C#, Java, C, C++, Software Design, Bluetooth, Low-level Programming, REST APIs, SQL, Subversion (SVN), Eclipse Memory Analyzer, Eclipse IDE, MonoDevelop, JNI, TFS, TeamCity, OkHttp, FFmpeg, NetBeans

Excel Macro Specialist

2007 - 2008
IBM
  • Created Excel macros using Visual Basic for Applications.
  • Worked with IBM Lotus Notes.
  • Built a connection between MS Excel and IBM Lotus Notus (using Microsoft Component Object Model).
  • Created an automated Excel document export with a combined data of more Excel files.
  • Developed automated emails with content and recipients generated based on the attached Excel document.
Technologies: Visual Basic, Microsoft Excel

Experience

Resco Mobile CRM

http://www.resco.net/mobilecrm/
A multiplatform mobile application for (not only) Microsoft Dynamics CRM.

Aevi Albert

A new kind of payment terminal using Android OS.

Chess.com

https://play.google.com/store/apps/details?id=com.chess
Play chess with more than 10 million players around the world and solve more than 50,000 puzzles. You can get access to thousands of videos and interactive lessons from top Grandmasters and many more features.

Indoor Touch 2.0

https://www.2n.cz/en_GB/products/answering-units/2n-indoor-touch-2
The 2N® Indoor Touch 2.0 answering unit guarantees reliable video door communication. The Android OS, more powerful hardware, and simple user interface make it easy to integrate the 2N® Indoor Touch 2.0 with third-party applications. For example, home automation systems can be comfortably operated on the 7“ touch screen made of tempered glass.

Skills

Libraries/APIs

Android API, WorkManager API, REST APIs, Fabric, FFmpeg, libVLC, Camera API, Google Maps, TensorFlow

Tools

Git, Jira, Android Studio, Android NDK, Microsoft Excel, Confluence, Gerrit, Jenkins, GitLab, GitLab CI/CD, U-Boot, TeamCity, Subversion (SVN), Eclipse Memory Analyzer, MonoDevelop, TFS, Eclipse IDE, Docker Compose, You Only Look Once (YOLO), Xcode

Languages

C, Java, C++, Kotlin, Embedded C++, Embedded C, Visual Basic, Python, C#, SQL, XML, JavaScript

Frameworks

Android SDK, JNI, Compose Multiplatform, .NET, Espresso, Appium, Dagger, Dagger 2, GStreamer, TensorFlow Lite

Platforms

Android, Linux, Embedded Linux, J2ME, NetBeans, Android TV, MacOS, Bluetooth Low Energy (LE), iOS, Docker, Firebase

Paradigms

Model View ViewModel (MVVM), Model View Presenter (MVP), Scrum, Agile Software Development, Test-driven Development (TDD), Unit Testing

Other

Low-level Programming, Jetpack Compose, Observer Pattern, Embedded Development, Software Design, Embedded Systems, Android HAL, Room, Kotlin Multiplatform, MonoDroid, Amplitude, Linux Kernel, Linux Kernel Drivers, ARM Embedded, FreeRTOS, Bootloaders, OkHttp, Digital Rights Management (DRM), Bluetooth, AOSP, Android Rooting, Android Emulators, Architecture, Android Kernel, Device Drivers, GPS, Location Services and Maps, Coroutines, Hilt, USB, UI Testing, Ultralytics, Jitsi, Roboflow, UVC

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