Rebuild Legacy Android Billing App

@Rajoriadares

Hello Client, Greeting of the day!!!! I read your job description. I can do this job with quality product. I am always available for your support. Thanks

@AZTURK1

Hi there, I understand you lost the source and need the legacy Android billing app recovered or rebuilt; I can extract logic from the signed APK and deliver a modern Kotlin project compatible with Android 8-14 with Material UI and Google Play-ready AAB. - Analyse APK with Jadx/Apktool, map workflows via your screen-capture, recover models and business logic - Rebuild app in Android Studio (Kotlin), implement billing/invoicing, customer management, reporting - Add inventory management, secure auth (email/biometric recommended), produce debug APK + signed AAB - QA: staged testing, rollback plan, and daily iterative builds with your feedback Skills: ✅ billing and invoicing ✅ Android Studio ✅ Jadx / Apktool reverse engineering ✅ Google Play AAB release / CI integration ✅ biometric/email auth, secure storage, performance hardening Certificates: ✅ Microsoft® Certified: MCSA | MCSE | MCT ✅ cPanel® & WHM Certified CWSA-2 I can start immediately, deliver a first runnable build within the agreed timeline, and iterate daily. Do you prefer I attempt a full decompile-first recovery (Jadx/Apktool) or proceed directly to a Kotlin rebuild to match the screens you provide? Best regards,

@Ak230598

Hello, I CAN DO THIS. I have 6.5+ years of experience in this field. Let's connect and discuss more about your requirements. Thank you.

@technologiesit

As a seasoned mobile developer with over a decade of experience, I possess the versatile skill-set required to successfully reconstruct or reverse-engineer your legacy Android billing app. In addition to being well-versed in Java, I am also competent in Kotlin, which you implied would be ideal for the task at hand. To ensure that your rebuilt billing app maintains its desired workflow, I will carry out a meticulous analysis of your provided APK and screen-capture in order to decipher its logic, layout, and data flow accurately. As an added bonus, my team consists of 20+ professional developers who can provide support whenever necessary. We understand speed is essential therefore we promote daily testing and have internal mechanisms to foster fast iteration. Lastly, given the histories of my long term clients as part of my core beliefs it is ensuring not only project success but client satisfaction long after the project's delivery; you being part of this philosophy will be no exception. With Prajapati Technologies, you get precisely what you need to improve your app - quality work and the best suggestions. Let's rebuild this app together!

@anirudhat

I've handled legacy Android recoveries before and know exactly what's involved—I'll start by decompiling your APK with jadx and Apktool to extract layouts, resources, and as much business logic as possible, then use your screen-capture walkthrough to map every billing, invoicing, and customer-management flow so nothing gets lost in translation. From there I'll rebuild the project in Kotlin using Android Studio with Jetpack libraries and Material 3 components, targeting API 26 through 34 for full Android 8–14 coverage. For authentication I'd recommend Firebase Auth with email/password plus biometric unlock, which satisfies current Google Play requirements and scales easily to social sign-in later. I'll integrate the new inventory module alongside your existing reporting and analytics features using a clean MVVM architecture with Room for local data, and I can start immediately—happy to work in short daily iteration cycles with you to validate each module against your real business workflow.

@yashvendra79

As a seasoned and versatile Android developer, I am confident in my ability to tackle the challenge of rebuilding your legacy billing! My team and I have over 10 years of experience in all major development technologies, which has equipped us with a deep understanding of Android architecture and coding structures. We are comfortable working with both Kotlin and Java, ensuring that we can tackle this project in a way that aligns with your preferences. When it comes to decompiling APKs or rebuilding from scratch, we believe in a meticulous approach that ensures accuracy without compromising on efficiency. We usually deploy tools like Jadx or Apktool for reverse engineering, but given the complexity of this project’s needs, we would determine our optimal tool only after reviewing the APK. As an experienced team, we highly value clean and well-commented code, making future maintenance a breeze. The deliverables you seek - a complete Android Studio project with robust documentation , working debug APK and release-signed AAB - are definitely deliverables that we can provide with confidence. Our familiarity with Material components and industry relevant libraries will ensure a smooth modernizing of UI, while your user-athentication layer will be built keeping in mind both convenience for your customers and abiding with all guidelines set by Google Play. Choose us for reliability, expertise, quality and above all cost-effectiveness for your project.

@QuickMentor

Rebuild Legacy Android Billing App I'm excited after reviewing your project details! With over 5 years of hands-on experience in Web and App Development, I specialize in building high-performing, user-friendly, and fully responsive digital solutions tailored to your business needs. I hold an academic background in Computer Science and have successfully delivered numerous projects across various industries. My expertise includes: Custom Website Development (React, Angular, Laravel, PHP, WordPress, etc.) Mobile App Development (iOS, Android, Flutter, React Native) E-commerce & CMS Solutions (Shopify, WooCommerce, Magento) API Integration & Backend Development UI/UX Design & Prototyping Bug Fixing, Speed Optimization & Maintenance ✔ Clean, Scalable & Secure Code ✔ 100% Mobile & SEO-Friendly ✔ Ongoing Support & Unlimited Revisions Let’s turn your idea into a powerful digital product that exceeds expectations! Check my profile: https://www.freelancer.com/u/QuickMentor Looking forward to working with you!

@balajinaagarajan

Dear Client, I will analyze your signed APK using Apktool to recover core logic, and if needed rebuild it from scratch in latest Android Studio, preserving billing, customers, and reporting while adding inventory and secure authentication as per Google Play guidelines. I am ready for fast daily iterations, and we have a dedicated Android team supporting development and QA. Thanks.

@Chrism276

EXPERT ((Android, Java, Mobile App Development, Android Studio, Kotlin, Android App Development, Billing and C# Programming)) DEAR EMPLOYER, I’ve completed the exact same projects before successfully. Awarding me will be the fastest way to complete your task with the best rates possible. I CAN ASSURE YOU 100% THAT WE ARE FULLY CAPABLE OF EXECUTING ANY LEVEL OF TASK/PROJECT BASED ON THE SKILL REQUIRED. I am fully confident about our skills and my understanding of the project description and we are ready to go through any test or sample task you assign to acquire your trust. Let me know when are you available for an initial 15-30-minute discussion (FREE OF CHARGE) so we can discuss the requirement in detail and I can walk you through the mentioned systems to acquire your trust in my skill. REST ASSURED YOUR WORK IS IN VERY SAFE AND PROFESSIONAL HANDS. THANK YOU

@hxptechnologies

Hi there ?, I’ve carefully reviewed your project titled "Rebuild Legacy Android Billing App" and can confidently deliver a production-ready solution with clean UI and smooth performance. Let's discuss your specific requirements — I can start right away!

@sumit31jaiswal

I have 5 years experience in mobile developer profile. Let's connect for further discussion. I have also knowledge about to pushed app to app store and play store

@jyotsnaa8

I would begin by analyzing the signed APK using tools like: • JADX for high-level Java code inspection • Apktool for resources and manifest extraction • Android Studio APK Analyzer for dependency and structure overview This phase would help reconstruct: • Core billing workflow logic • Data models and database structure • API integrations (if any) • Existing calculation rules for invoices and reports However, instead of attempting to reuse decompiled code directly (which is often unstable and hard to maintain), I would treat the APK as a reference blueprint and rebuild the project cleanly in Kotlin using modern Android architecture principles.

@izanRobles

Buenas tardes. Entiendo que no me conoce, pero resuelvo problemas similares a diario en mi carrera y en mis proyectos personales. Estoy buscando empezar a ganar review y experiencia en este mundillo por lo que hago lo que considero una buena oferta. Muchas gracias por su consideración y un saludo. Izan Robles.

@crismicheal

I recently helped a client recover and modernize a legacy Android app by decompiling their APK and rebuilding key features in Kotlin, resulting in a stable, future-proof app compatible up to Android 13. I bring 5+ years of hands-on experience and a track record of delivering high-quality, practical solutions. I keep projects organized, communicate clearly, and ensure deadlines are met. My goal is simple: efficient execution and a result you’re proud of. I can start right away. While I am new to Freelancer, I have tons of experience and have done other projects off site. I would love to chat more about your project! Regards, Cristiano Ferreira

@chandrupondy

Hello, I have carefully reviewed your requirement regarding recovery and modernization of your Android billing application. Whether through structured decompilation of the signed APK or a full rebuild in the latest Android Studio, I can help you restore and future-proof your app while preserving its core workflow. Approach: 1. APK Analysis: I will first inspect the APK using tools such as JADX and Apktool to recover as much readable logic, resources, and structure as possible. This helps map business rules, database schema, and workflow. 2. Architecture Planning: Based on findings, I will recreate the project in Android Studio using Kotlin (preferred) with a clean MVVM architecture and Material Design components. 3. Feature Reconstruction:Billing & invoicing, customer management, reporting/analytics will be rebuilt faithfully, followed by integration of inventory management and a secure authentication layer (Firebase Auth with email/password + optional biometric is a practical, Google Play–compliant approach). 4. Compatibility:Ensure stable performance from Android 8 to Android 14 with updated SDK targets. I have experience rebuilding legacy Android apps where source code was unavailable, ensuring clean architecture and long-term maintainability. I’m ready to review the APK and screen recording immediately and begin with a structured recovery plan. Best regards, Hemachandhiran A

@sanketpatil51515

Hi, I’m Sanket, an Android developer experienced in rebuilding legacy apps and modernising them with clean architecture in Kotlin. Since you only have the signed APK, I would first analyze and recover the logic, not rely blindly on decompilation. My Approach Phase 1 – APK Analysis • Use Jadx + Apktool to inspect layouts, flow, API calls • Extract resource structure (XML, assets, strings) • Document workflow (billing → customer → reports logic) If code recovery is clean enough, we reuse logic. If obfuscated/heavily optimised, I rebuild from scratch using your screen recording as functional reference (recommended for long-term stability). Phase 2 – Modern Rebuild • Kotlin + MVVM architecture • Room (local DB) • Material 3 UI • Inventory management module • Secure auth layer (Email + optional biometric via AndroidX Biometric) • Compatible Android 8–14 Deliverables • Clean Android Studio project • Debug APK + signed AAB • Billing, customers, reporting, inventory, auth modules • Documentation (structure + libraries + build steps) I prefer rebuilding cleanly rather than shipping fragile reverse-engineered code. Ready to review your APK and screen demo. — Sanket

@sakshigweb

Hello, You’re not just trying to recover an old APK—you’re trying to preserve a proven billing workflow while modernising it for today’s Android standards. That distinction is important, and it’s how I’d approach this correctly. Here’s how I’d handle the job end to end: • APK Analysis: Review the signed APK and screen-capture to understand logic, data flow, and UI behaviour • Recovery Strategy: Use tools like Jadx/Apktool only to extract structure and logic references—rebuilding cleanly where decompiled code isn’t reliable • Rebuild in Android Studio: Modern Kotlin-based project (Java where needed), structured and future-proof • Core Features: Billing & invoicing, customer management, reporting & analytics rebuilt to match existing workflows • Enhancements: Add inventory management and a secure authentication layer aligned with current Google Play guidelines • UI Modernisation: Material components for a clean, modern interface across Android 8–14 • Delivery: Debug APK, release-ready AAB, and clear documentation for maintenance and extension The focus is stability, clarity, and long-term maintainability—not just making the app “work” again. I prefer aligning on the existing workflow and recovery approach first, then refining scope together. Once we’re clear on expectations, we can comfortably discuss budget—delivering a solid, dependable rebuild is always the priority. Looking forward to reviewing the APK and walkthrough.

@mashayac

Am interested in helping u on your project all I can say is that I have a lot of experience because I used to work at a company that has to do with your project

@zacsin9

Hey — saw your post about rebuilding your legacy Android billing app from just the signed APK. The tricky part here is preserving the exact workflow logic (billing, customers, reports) while modernizing everything and not breaking how you actually use it day to day. Quick question before I suggest a concrete approach: Do you want me to attempt a structured decompile first (Jadx/Apktool) to recover logic and DB structures, or are you leaning toward a clean Kotlin rebuild that just uses the APK + screen recording as a functional spec? I’ve rebuilt older Android apps from APK-only before, using Jadx + Apktool to map flows, then recreating them in a fresh Kotlin + Material 3 project targeting Android 8–14 with proper auth layers. If you send the APK and the screen-capture, I’ll review them and outline how I’d map the existing flows, choose the auth method, and estimate a timeline to your first runnable build.