6+ years
Flutter Development
- Cross-platform mobile apps
- State management (BLoC, Riverpod)
- Platform channels & native integration
- Custom widgets & animations
- Performance optimization
Available for Projects
Roland Wimmer
Flutter Developer Expert & Trainer
12+ years building
scalable mobile solutions
📱 Flutter
50+
Apps Delivered
🏢 Enterprise
20+
International Clients
📋
Legacy Modernization
I analyze your existing systems and architect a migration path that minimizes risk while maximizing business continuity
🏗️
Enterprise Apps
I build scalable mobile solutions using Clean Architecture, SOLID principles, and comprehensive testing strategies
🎓
Flutter & Dart Trainer
I empower your team with hands-on workshops and mentoring to ensure sustainable development practices
Technical Expertise
Specialized in building and improving enterprise-grade mobile applications with a focus on maintainability, scalability, and developer experience
10+ years
Enterprise Solutions
- Large-scale refactoring
- Legacy code modernization
- CI/CD pipeline setup
- Team mentoring & code reviews
- Architecture documentation
10+ years
Testing & Quality
- Test-Driven Development (TDD)
- Unit & Integration testing
- UI testing & automation
- Code coverage optimization
- Performance profiling
12+ years
Android Native
- Kotlin & Java expertise
- MVVM & Clean Architecture
- Jetpack Compose
- Dependency Injection (Dagger/Hilt)
- Reactive programming (RxJava, Coroutines)
Featured Portfolio
Enterprise applications that have transformed businesses and improved experiences for millions of users
2026
2025
2024
2023
2022
2021
2020
2019
2018
2017
2016
2015
2014
2013
2012
Wolf
MyWolf
Offline-first heating equipment setup app for partners and technicians with streamlined CI pipeline and golden test framework
✓ Improved team efficiency, revamped offline caching for better reliability/performance, replaced flaky E2E tests
Bayer
MagicScout
Agricultural optimization app helping farmers improve day-to-day operations with Clean Architecture
✓ Refactored from PoC to production with 100% test coverage in critical layers
Railsoft
Railsoft
Flutter app built from scratch with clean architecture and local-first caching strategy for full offline capability
✓ Ensured robust backend sync with state management via Riverpod and automated builds via CodeMagic
Blackned
Ridux Collaboration Client
High-security Android collaboration platform with proprietary software stack
✓ Developed secure communication client under strict NDAs
Viessmann
Flutter Training Program
Comprehensive Flutter training for 9 internal developers covering Dart, state management, and enterprise patterns
✓ Enabled Viessmann to build internal Flutter capabilities
Telekom
Vjumi Platform
Base app structure and architecture for Telekom's new Flutter platform
✓ Trained internal team on Clean Architecture, TDD, and Flutter best practices
MediaMarkt/Saturn
MediaMarkt/Saturn App
Complete redesign and migration to Flutter of Europe's largest electronics retailer app serving millions across 11+ countries
✓ Reduced development time by 40%, scaled team from 3 to 10 developers
MediaMarktSaturn
MediaMarkt/Saturn Hybrid Apps
Hybrid Android & Flutter apps for 11+ countries with GraphQL backend
✓ Architected transition from native to Flutter, scaled team from 3 to 10 developers
MealPro
mealPro
B2B white-label canteen digitalization app with multi-tenant architecture
✓ Built fully automated CI/CD with Fastlane for multiple white-label builds
REWE Group
REWE Digital Shopping
Enhanced grocery shopping experience with real-time inventory and personalized recommendations
✓ Improved app performance by 60%, implemented offline-first architecture
foodsharity
foodsharity
Cross-platform food sharing app with TypeScript backend
✓ Led technical architecture for both mobile app and backend infrastructure
Vodafone
Vodafone Wallet
Award-winning mobile payment solution with NFC support and digital identity management
✓ Won 4 industry awards including Overall Winner 2016, processed millions in transactions
Vodafone
Access UK
Access solution transitioning from plastic cards to SIM-based authentication
✓ Developed innovative NFC/SIM card access system with AWS backend
Vodafone
Passbook SDK
Android SDK library for Vodafone Wallet passbook functionality
✓ Created core SDK powering award-winning Vodafone Wallet app
WDR
WDR Media Platform
Modernized Germany's largest state broadcaster app with live streaming and on-demand content
✓ Increased user engagement by 150%, reduced crashes by 95%
Stellantis/Opel
CarUnity
Innovative car-sharing platform for Opel vehicles
✓ Delivered core Android app functionality for new mobility service
Sparkasse
SparkassenScan
Augmented reality app for Germany's largest banking group
✓ Pioneered AR banking experiences using metaio SDK
Huber Verlag
Tattoo-Erotica AR
Augmented reality app for Germany's biggest erotic tattoo magazine
✓ Pioneered AR experiences in publishing industry
Schuster Energie
Switch Box App
Android tablet solution modernizing electronic control systems with Modbus Protocol
✓ Replaced legacy membrane keyboards with modern Android interface
grAPPfruit
A Word! Game
Multiplayer mobile game built with Unity3D and custom backend
✓ Designed and developed complete game with client-server architecture
marktcom.de
marktcom Flohmarkt App
Mobile marketplace app for Germany's flea market platform
✓ Delivered native Android app with REST API integration
Die MedienPartner
Internal AR Apps
Multiple augmented reality demo applications
✓ Created AR showcase portfolio for client demonstrations
Eli Logistics Solutions
Internal Logistics App
Augmented reality logistics application
✓ Delivered AR-based logistics solution to Google Play
ADAC
ADAC Camping Guide
Europe's leading camping guide app with offline maps and booking integration
✓ Architected scalable solution handling 500K+ active users
today
Interested in learning more about my approach to enterprise development?
Let's Discuss Your ProjectTrusted By Industry Leaders
I've had the privilege to work with some of Germany's most innovative companies, delivering solutions that impact millions of users
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Global life sciences leader in healthcare & agriculture -
Europe's largest telecommunications provider -
German automotive manufacturer -
Germany's second-largest grocery retailer -
Global telecom leader, world's 6th largest mobile operator -
Europe's leading consumer electronics retailer -
German savings banks network -
Europe's largest automobile club -
Heating, cooling & climate solutions -
Climate solutions & heating systems -
Germany's largest regional broadcaster (ARD member) -
High-security software solutions -
Digital railway infrastructure solutions -
Industrial automation & energy systems -
Online flea market platform - ... and many more
"Working with enterprise clients has taught me that successful digital transformation isn't just about writing code—it's about understanding business needs, mentoring teams, and building sustainable solutions that scale."— Roland Wimmer
Let's Build Something Great
Whether you need to modernize your mobile architecture, build a new Flutter app, or improve your development processes, I'm here to help
roland.wimmer@grappfruit.com
linkedin.com/in/grappfruit
GitHub
github.com/grappfruit
Medium
@roland.wimmer
Available for Projects
Ready to Transform Your Mobile Strategy?
I specialize in helping enterprises modernize their mobile applications, implement clean architecture, and build high-performance Flutter apps. Let's discuss how I can add value to your team.