Android navigation app jobs

I'm looking for a professional in supermarket design to help with the layout of my store. It's important to me that the design is classic and traditional. Key areas of focus: - Checkout Area: A welcoming and efficient checkout area is a priority. - Product Placement: I'm looking for a design that encourages customer engagement and sales, so product placement is key. - Aisles & Walkways: E...experience in supermarket or retail space design. - Understanding of customer flow and experience in retail settings. - Ability to balance traditional design with modern functionality. - Familiarity with maximizing product exposure and space efficiency in retail environments. I'm aiming for a design that combines the nostalgic feel of classic supermarkets with a modern appro...

We are looking for a skilled Rive developer who can help us completely reskin a Flutter-based poker app for both mobile and PC platforms. The main task will be to redesign the user interface and give the app a fresh look and feel. We want it to be similar enough to the market leading mobile poker apps like X-Poker for player familiarity but with our own twist. We aim to launch by 1st August 2024. You can download X-Poker here to get an idea. The reskinning work will include but not be limited to: - Menu design and navigation (Player balance display, cashier, game selection menus/filters, settings) - Card graphics and animations (dealing, folding, community cards, winning/losing hand highlight/shadow) - Chip graphics and animations (betting, calling, chips collecting ...

I have built an Android app in Android Studio (Iguana) but I cannot figure out how to upload it to the Google Play store. Hence, I am seeking a qualified freelancer to provide a 1-hour virtual tutorial explaining the app submission process. I want to be on VTC and share my screen while someone guides me through the process. This tutorial should primarily focus on: - The process of submitting an app to the store. - Understanding the app store's guidelines. - Tips on app signing and security. Upon successful completion of the class, an opportunity to build additional apps may arise. Remember, the ideal freelancer should have verifiable experience in Android app development, app store submissions and previous ...

...Integration: Integrate the Vue.js components with the Laravel backend to ensure seamless data flow and functionality. API Development: Develop any necessary APIs in Laravel to facilitate frontend-backend communication. Data Binding and State Management: Implement data binding and state management using Vuex or other appropriate methods. Routing: Set up routing in Vue.js using Vue Router to enable navigation within the application. Validation and Error Handling: Implement form validation and error handling on both frontend and backend to ensure data integrity and security. Optimization and Performance: Optimize the application for performance and scalability, considering factors like caching, code splitting, and lazy loading. Testing: Write unit tests for frontend and backen...

...need of a competent developer to create a QR-based payment system app. The application should be designed for Android ,IOS, and Web platforms. The key features to be incorporated are: - QR Code Generation: The app should enable the generation of QR codes. This function is crucial as it will allow users to create their unique codes for payments. - QR Code Scanning: The application should equip users with the ability to scan QR codes. This process should be intuitive and user-friendly. - Payment Processing: An integral function of the app will be facilitating payments. It will be designed to process transactions seamlessly. The app is to support Standard QR code format - no dynamic or customized codes are needed. I expect the app to be secure, r...

Already have App in Flutter, ClickCar is my App name, please check app and its existing functionality first before you bid I'm in need of a skilled app developer to create a new saperate apps for me from the old app concept (Old App name = ClickCar). The app will be a platform for buying and selling used cars. Key Features: - User Profiles: Users should be able to create detailed profiles to engage with the app - The app will be developed for both iOS and Android platforms Ideal skills for this project include proficiency in app development for both iOS and Android, an understanding of e-commerce functionality, and experience in creating platforms for buying and selling items.

I'm looking for an Android developer to assist with the generation of an AAB file and its subsequent upload to the Google Play Store. Key Duties: - Generate AAB file: I need you to take care of the technicalities in creating and refining the AAB file for the Android App. - Upload to Play Store: I already have a Google Play Developer account. You'll be responsible for the successful uploading of the AAB file to the platform. Please note: - The app's functionality and content comply with Google Play Developer Policy. - There is no immediate need for you to be involved in the development of the app itself. Ideal Freelancer: - Proven experience in Android development. - Familiarity with the process of generating AAB files and uploading to...

I'm looking for a talented and experienced app developer to build an informational app for both iOS and Android platforms. Here's what I need: - Proficiency in developing apps for both iOS and Android - Strong UX/UI skills to create an intuitive and attractive design - Ability to ensure seamless performance across all devices While I haven't specified features at this point, I require guidance from you on that, so your creativity and familiarity with the latest trends in app design will be highly valued. Although the primary purpose of the app is informational, having experience in integrating e-commerce or social networking features may be beneficial for future updates. Please provide a portfolio or examples of similar work done...

I'm in need of an expert who can convert my web application to a native app for both iOS and Android. Key Requirements: - The primary function of this app is content sharing. It should maintain the same level of functionality and user experience as the web app. - The app must also include a payment processing integration. Your responsibilities will include: - Wrapping the web app using Bravo Studios to ensure it runs smoothly on both iOS and Android platforms. - Ensuring seamless connectivity with the web app's existing backend for content sharing. - Implementing a secure and reliable payment processing system within the app. Ideal Skills and Experience: - Proficiency in both and Bravo Studios. - Prior experience in c...

I require expertise in mobile tracking specific to Android, with the focus on deep analysis of Whatsapp chats. - Data Extraction: The service should comprehensively extract media files that include photos, videos, and audio. Additionally, text messages and even deleted chat history need to be obtained. - Accessibility: I currently have physical access to the target Android device for the required setup or software installation. Ideal Skills: - Proficiency in Android OS and understanding Whatsapp functionalities. - Experience with data extraction and recovery. - Familiarity with mobile tracking and surveillance tools. Your task will be both challenging and sensitive, demanding utmost ethics and discretion.

I'm on the hunt for a seasoned Full Stack Developer with an exceptional eye for design. The goal at hand is to freshen up my PHP-powered website, with a keen focus on engaging aesthetics and smooth user experience. Key Improvements: - Redesign the homepage to achieve a modern, clean aesthetic that aligns with our brand - Rework navigation and menu layout to ensure seamless user browsing - Enhance visual elements and graphics to captivate and hold user attention Ideally, I'm looking for someone with proven experience in website design and coding, especially PHP. Unfortunately, I cannot provide specific details on what your application should include, but presenting evidence of your previous work will definitely give you a leg-up.

I'm looking for a skilled professional with dual expertise in both Android development and UX design. Key Goals & Responsibilities: - Improve user experience and aesthetics of my existing Kotlin Android application. - Enhance the app's look, colour, navigation, usability, and responsiveness. - Conduct code refactoring to ensure optimal performance. Proper understanding and experience in the following are crucial: - Android application development. - UX design practices. - Code refactoring, optimization and enhancing performance. - Visual aesthetics, and robust navigation systems. Your primary focus would be to revamp the app to make it more user friendly, agile and aesthetically pleasing. If you have sucessfully handled similar pro...

I am seeking to hire an experienced app developer to build an Android-based application with the primary focus on providing information to our specific target group, teens and young adults. Key project requirements: - Development of an informational Android app. - The material must be suitable and engaging for teens and young adults. - Appealing design that attracts our target audience. Ideally, the freelancer should have: - Prior experience in creating informational apps. - Exceptional skills in Android app development. - Understanding of teenager and young adult interests or previous project experience targeting this specific age group. - The ability to work efficiently and deliver the project within agreed deadlines.

I am seeking a skilled android app developer to create an Angel one Sub broker trading app with a focus on long-term investing. The developer should be versed in financial systems, specifically related to trading functionalities. Key Features Required: - Real-time stock quotes - Portfolio management - Trading alerts - Long-term investing support Experience with developing trading apps, or in the financial sector would be beneficial. Proficiency in creating intuitive and user-friendly interfaces for Android systems is crucial. The end product should be reliable, efficient, and effective for constant use in the long-term trading landscape.

As a client, I'm seeking an experienced developer to create an innovative Android application. The primary goal of this project is to develop a mobile app that allows users to earn through playing games. Key Features: - The app should mainly focus on adventure games. - Users should be able to earn points or real money through in-app activities. - The application should have a sleek and user-friendly interface. Ideal Skills and Experience: - Proficiency in Android app development. - Experience in developing gaming applications. - Familiarity with monetization strategies in mobile applications. - Strong UI/UX design skills to ensure a seamless user experience. This project offers an exciting opportunity for a skilled developer to create a u...

We are in need of a talented Android game developer for small, periodic tasks. Key Responsibilities: - Developing Android games, the type of the game will change depending on the task. Ideal Candidate: - Prior experience in developing Android games is a must. - Proficiency in Java and Unity. - Strong problem-solving skills. - Ability to work in a fast-paced environment and deliver quality work under tight deadlines. Please submit your proposal including past examples of your games and your availability for short tasks.

I'm seeking an experienced app developer to create an educational Android app with quiz functionality. Key Features: - The app needs to have a user-friendly interface for students to access educational content and take quizzes. - The quiz functionality should allow me to create and manage different types of questions. - The app should track user progress and provide performance analytics. Ideal Candidate: - Should have experience in developing Android apps. - A strong background in creating educational apps with quiz functionality. - Proficiency in UI/UX design for an engaging user experience. - Previous experience in building apps that track and analyze user data for educational purposes will be a plus. Please include samples of previous...

I'm seeking a seasoned mobile app developer to create an Android application. This app will primarily function as an accounting tool, specifically focused on recurring transaction recording. Key Features: - The app should allow users to log recurring transactions effectively. - It's essential that the application provides robust and user-friendly features for efficient accounting. Ideal Skills and Experience: - Proficient in Android app development. - Previous experience in creating similar applications with recurring transaction features. I'm looking for a freelancer who can bring both technical expertise and a solid grasp of accounting concepts to this project. Your ability to deliver a clean, functional, and user-friendly mob...

I'm looking for a skilled professional with dual expertise in both Android development and UX design. Key Goals & Responsibilities: - Improve user experience and aesthetics of my existing Kotlin Android application. - Enhance the app's look, colour, navigation, usability, and responsiveness. - Conduct code refactoring to ensure optimal performance. Proper understanding and experience in the following are crucial: - Android application development. - UX design practices. - Code refactoring, optimization and enhancing performance. - Visual aesthetics, and robust navigation systems. Your primary focus would be to revamp the app to make it more user friendly, agile and aesthetically pleasing. If you have sucessfully handled similar p...

I am looking for a seasoned mobile app developer who can create a robust e-commerce app for both iOS and Android platforms. The app is primarily focused on facilitating cash debit and cridet should include the following key features: - User registration and login: A streamlined, secure process for users to register and log in to the app. - Product catalog: An extensive and well-organized catalog showcasing a variety of products. - Shopping cart: A functional and user-friendly shopping cart that enables smooth transactions and easy checkout. The ideal candidate should have prior experience in developing e-commerce applications, with a keen understanding of both iOS and Android platforms. A strong background in user authentication and database mana...

I'm looking for an experienced Android developer to join my project. Although I haven't specified the exact type of app or its purpose yet, I can tell you it'll be important for you to be proficient in the following areas: - Java programming - Android Studio - UI/UX design Please only bid if you are comfortable with the above skills and have a vast experience in Android development. I'll provide further details about the project to the right candidate. Thank you.

I need an experienced app developer to create a dine-in concept app. This platform is set to be both Android and iOS compatible. Your experience with these platforms, and with creating functional, user-friendly interfaces, will greatly contribute to this project. KEY FEATURES: - Table Reservation: Enable users to reserve tables with ease. - Menu Browsing: Users should be able to browse the menu thoroughly and conveniently. - Order Placement: Facilitate the entire ordering process through the app. - able to scan QR code to place order and pay. DESIGN PREFERENCES: - The aesthetic of application should lean towards the colorful side. I am expecting a lively interface that will leave an impression on the users. PLEASE NOTE: - I understand the risks of online scam...

I'm experiencing crashing and UI/UX issues with my existing Android App. I haven't made any recent updates to the app, but these issues have become prevalent in the last few weeks. Key Responsibilities: - Pinpoint and resolve the crashing issues in the app - Enhance the user experience and interface to make the app more appealing and user-friendly. Ideal Skills and Experience: - Proven experience in Android app debugging. - Strong familiarity with UI/UX principles. - Ability to work efficiently and independently. Please share your relevant experience and approach to this type of project.

...Learning, MS Copilot, Cloud Computing (Azure), MS Power Platform, SQL Server, iOS, Android, and comprehensive Microsoft technologies. Preference will be given to candidates in the USA time zone. Key Details: - Main Objective: The main goal of this project is to develop a new software application. - Platforms: The application will be developed for Web, iOS and Android. Ideal Skills & Experience: - Proficient in Artificial Intelligence and Machine Learning with a proven track record in similar projects. - Expertise in MS Copilot, Cloud Computing (Azure), MS Power Platform, SQL Server, iOS, Android, and Microsoft technologies. - Prior experience in developing cross-platform applications for Web, iOS and Android. - Ability to work effectively within the US...

...skilled UX and Android developer to breathe new life into my app's user interface and streamline the backend code. This revamp includes: - Updating the color scheme. Despite skipping the specific color scheme preferences, I'm eager to discuss creative inputs from the chosen freelancer for this. - Making layout modifications. This involves reorganizing elements for better user experience, adding new sections to increase app functionality and simplifying navigation to promote user ease. The ideal candidate will have an eye for sleek, user-friendly design and possess the ability to transform these designs into efficient code. Also, keen understanding of UX principles and Android development experience is required. Understanding the nuances of layou...

I am looking for an experienced Android developer to create a doctor's appointment application. The app should include the following features: - Login and Registration: Users should be able to create accounts and log in securely to access the app's services. - Booking and Scheduling Appointments: The app should allow patients to book appointments with doctors and schedule them efficiently. - Reminders and Notifications: Implement a system of reminders and notifications to keep both patients and doctors informed about their appointments. Required Skills and Experience: - Proficiency in Android app development - Experience with implementing user authentication systems - Strong knowledge of in-app booking and scheduling features - Prior ex...

I'm looking for a comprehensive market research on voice changing AI applications that can function with the "Salaams" app on iOS and Android platforms. It's crucial that these applications have a real-time voice changer feature. I'm specifically interested in applications that can shift voice to a non-cartoonish, non-robotic female voice. Ideal Skills and Experience: - Extensive experience in AI app research - Detailed understanding of voice changer apps - Familiarity with Salaams app and its compatibilities Project Requirements: - Identify compatible voice changing AI apps for both iOS and Android - Focus on apps providing real-time voice change to a female voice - Exclude apps producing cartoonish or robotic voices - Deliver...

Hi! I'm looking for a skilled Flutter developer to create a Point of Sale (POS) app for Android. Application is already in progress. You need to make it offline. Your previous experience in sqflite is plus.

I need a specialist to transform my existing WordPress site into a modern, user-friendly mobile application for both iOS and Android platforms. The mobile app should include the following WordPress site features: - Bidding on request for quotations - Shopping cart functionality - User reviews The design should be sleek and modern. Ideal freelancers should have extensive experience in mobile app development, specifically in converting WordPress sites to mobile apps. Knowledge in modern UX/UI design is beneficial to this project, as is a solid understanding of e-commerce functionality.

I'm looking for an experienced Android developer to create an educational application in Kotlin. This app will provide solutions for Class 10 NCERT textbooks. The main feature of the app will be the provision of detailed and accurate solutions for the textbook questions. Key Features: - Development of a user-friendly interface for easy navigation through various subjects and chapters from the Class 10 NCERT curriculum. - Integration of Banner ads in non-intrusive areas of the app to generate revenue. Important Notes: - This project does not require a user login system. The main focus is on providing reliable solutions for the materials. - The developer must be proficient in Kotlin and have a good understanding of mobile application development for...

...stunning dropshipping fashion store from scratch. This project involves customizing the theme, product layout, and potentially setting up a payment gateway. Key requirements: - **Theme Customization**: Crafting a unique, appealing, and user-friendly design that aligns with the fashion niche. - **Product Layout Customization**: Organizing our large inventory of 15,000 products to ensure easy navigation and a smooth user experience. - **Payment Gateway Setup**: Potentially integrating a payment gateway, ensuring smooth and secure transactions. Additional context: - **Branding and Logo**: As I'm starting from scratch, I'll need assistance in creating a logo and establishing a cohesive branding strategy for the store. Ideal candidates should have: - Proven experience i...

I want an android developer with java, php, laravel, api Working on android studio and laravel app control panel

I'm in need of a professional web designer to create an engaging and classic looking survey interface for my mystery shopper project. The design should prioritize user-friendly navigation, ensuring participants can easily progress through the survey. Crucially, the design must be responsive and adaptable to a range of devices. Ideal skills for the job: * Web design experience, particularly with surveys or similar interactive interfaces. * Expertise in creating a 'classic professional look'. * Ability to implement features such as: To create a webpage that displays a Mystery shopper job description along with an application form. The website should allow applicants to fill out the form, and upon submission, I should receive the information they provided. However, befo...

UX. Below are some of the requirements and will be broken down into milestones. Work items (subject to change before the project starts, may have minor changes after project starts): Everything below shooul work on Chrome, Edge, Firefox and Safari of windows desktop, iphone and android. Please test on those browsers and let me know if you are not able to test on both mobile devices. We need too complete bugs first followed by enhancements. Some of the styling items may required a couple of back-and-forth requests to change things slightly. Bugs: a. When there are no results, we need to display a message at the top that of the no results page that says "No results found". (you can test it with price, RAM and CPU Speed set to highest values) b. When we click on Show detai...

I'm in need of experienced Android developers who can quickly upgrade my app to the latest version. Key Requirements: - Basic upgrades to support the latest version of Android - The application should run smoothly on the android 14 version The upgrade does not require the addition of new features, just ensuring the current functionality is maintained and improved to work seamlessly with the newest Android version. The project is of high priority and needs to be completed as soon as possible. Ideal Skills and Experience: - Proficiency in Android app development - Experience upgrading existing applications - Ability to work under tight deadlines - Strong understanding of the latest Android version Here's the link to the...

I'm looking for an android app developer to assist with daily maintenance tasks for my android app. Key Responsibilities: - Content Updates: Regularly update the app's content to keep it fresh and engaging for users. - Security Updates: Ensure the app is secure and protect from any vulnerabilities. - Bug Fixes: Identify and fix any bugs in the app to ensure smooth user experience. - Full Maintenance: Oversee all aspects of the app, including but not limited to updating content, security, and fixing bugs. The ideal candidate should have: - Proven experience in android app development and maintenance. - Strong understanding of mobile app security and bug fixing. - Ability to work on fast-paced projects and pro...

I'm looking for a skilled freelancer to completely transform the UI of my Laravel website. The main task is to improve upon: * Layout and Structure - Making the site visually appealing and organized. * Colors and Fonts - Choose a suitable color palette and fonts that complement each other to ensure usability and readability. * Navigation and User Experience - Streamline navigation and enhance user experience, making it intuitive and easy to move around the site. My ultimate goal is to enhance the overall brand image. I want to project a positive, memorable first impression to our site visitors. Although I don't have specific color or visual elements in mind, I am relying on your expertise to guide the aesthetic direction of the project. Skills and Experience N...

I'm seeking an experienced app developer to create a robust and user-friendly iOS and Android application. The app will also require seamless integration with social media platforms. Key Points: - should be like Amovan app on App Store - iOS Development: The app must be tailored specifically for iOS devices, ensuring a smooth and optimized user experience. App should connect/read/integrate data collected from smart ring device via bluetooth. Ideal Skills and Experience: - Proficient in iOS app development, with a portfolio demonstrating successful e-commerce app projects. - Prior experience with integrating social media platforms into mobile applications. - Strong understanding of payment gateway integration and e-commer...

I'm looking for a proficient app developer to create a taxi app with GPS live tracking integration. Key Features to Include: - Passenger pickup functionalities with tailored options specific for kids' after-school pick-up - Seamless GPS integration to provide accurate navigation and live tracking features - Secure payment gateway integration for hassle-free transactions - User rating system to maintain high-quality services Platform Compatibility: - The app should be developed for iOS, Android and also be cross-compatible. User Interface: - Registration/Login feature for users is a necessity to personalize the app experience and ensure data security. Ideal candidate should have previous experience in developing taxi apps and a stro...

We are seeking an experienced Flutter developer who specializes in building Android applications to help us generate an APK from our existing Flutter source code. The ideal candidate should have a strong understanding of the Flutter framework and the Android development

I'm in need of a talented web developer to build a website akin to ttspl...testimonials section to help build trust with prospective clients. - Downloadable content such as eBooks and whitepapers for user engagement and lead generation. As for the design, I'd appreciate creative input on the color scheme and brand identity elements. While there aren't any strict guidelines to follow, the design should be professional, engaging, and user-friendly to facilitate easy navigation. Ideal candidates should have experience in web design, UI/UX, and site optimization, along with excellent communication and creativity skills to translate my vision into a compelling online presence. Familiarity with content creation for downloadables would be a significant advantage. Looking f...

I look forward to working with a skilled web designer to create an innovative website focused on showcasing properties for my real estate business. Primarily, I am interested in the following: I have this site now: I need that web page to look more prof Key Features: - A slick property search bar - Interactive virtual tours De...pages, each individually designed to captivate and retain user interest. Ideal Expertise: The ideal freelancer for this project will have diverse knowledge in web design, particularly related to real estate. The fundamental skills required will include HTML, CSS, JavaScript, and experience with virtual tour software. Prowess in UX/UI design will be an added advantage in order to ensure smooth navigation and an all-around exceptional user experience.

Mini Game VR Unity for Android

I need a few corrections on my website that are necessary to enhance the user experience. - I would like to improve the functionality of the Home Page in particular. - The key aspects that need attention include: - Fixing broken links that might be present. - Ensuring that all elements are working correctly. - Making sure that the website navigation is smooth and intuitive. The ideal freelancer for this job would have a solid understanding of web development and design principles. Experience in correcting website functionality issues is a plus. It's important that the changes are implemented thoroughly and tested extensively to ensure that the Home Page is working perfectly.

I need an expert React developer to work on my healthcare website ...project. As your primary task, you'll be responsible for both designing the front-end of the site and setting up the back-end database. It is critical that you have: - A strong grasp of React and database management - Prior experience with similar projects - Ability to implement requested features and functionalities, which are: - User registration and login - An appointment booking system - Navigation to the nearest pathology center - An AI ML tool for generating smart reports with graphical representation Make sure your application demonstrates your experience and expertise. Also note that while I do have a website design in mind, I’m looking forward to discussing how best we can implement th...

...measures to protect user data Project specifics: - Search engine is already functional, only improvements and a few customizations will be needed - Changes and adjustments are needed in the admin area, e.g. editing newsgroups and adjusting retention - A simple API for the search still needs to be implemented - Standardize the design of the website - Development of an extended search function for navigation in Usenet groups - User-friendly interface for account creation and login process - A design that adapts seamlessly to desktop and mobile devices - A clean user interface with an option to change simple seasonal themes e.g. Halloween, Christmas - Adjustments to the invite system and registration - Add Online Check for .NZB Files - Bring changes online and then make any necessa...

I'm in need of a skilled website developer to help create a professional web presence for my business. Key Features: - The primary goal of the website is to showcase our products and services to potential customers. No e-commerce functionality is needed at this time; a simple contact form should suffice for inquiries. - The website should have a clean and user-friendly design, with easy navigation across different pages. Key Pages: - Home Page: The landing spot that gives a brief overview of what we do and prompts visitors to explore further. - About Page: A section that provides background information on our company and its values. - Services Page: A detailed description of the services we offer and how they can benefit our clients. - Achievements: A page that highlights our...

I'm looking for a developer capable of creating a crash game prediction application for Android. The software should possess capabilities for historical data analysis and game result forecasting. Key features include: - Utilizing game statistics: The app should efficiently analyse and utilise game statistics to forecast results. - Forecast game results: The application should effectively predict outcomes based on analyzed historical data and present trends within the games. The ideal applicant should have experience in developing similar systems and a deep understanding of data analysis algorithms. Experience with gaming or betting systems would be a plus. Familiarity with Android application development is a must.

...mobile app developer to build an Android application for food delivery. The primary focus of this project is to create an app that offers an engaging user interface and efficient user experiences. Key Functionalities Needed: - Menu browsing and ordering: The application should allow users to easily view and place orders from a variety of menus. Preference for developers with experience integrating smooth and straightforward ordering processes. - Real-time order tracking: It is crucial for users to be able to track the progress of their orders in real-time. Experience designing and implementing effective order tracking systems will be highly advantageous. Please note, while not explicitly mentioned in the key functionalities, the ability to integrate future upgr...

I have been working on this project but i am stuck. I do want to share screen with you, and you help me in live to fix the problems and get the job done. I require an Android app built in Kotlin, adhering to the MVVM pattern and Google's design guidelines. The main functionality of the app will be a recyclerview displaying images retrieved from a JSON URL, integrating external sources through Retrofit and GsonConverterFactory. Key Requirements: - Android app development in Kotlin - Proficiency in MVVM pattern - Adherence to Google's design guidelines - Implementation of a recyclerview displaying images - Integration with an external JSON URL using Retrofit and GsonConverterFactory