🍽️ TestApp

A reference Android application for students

An educational example project demonstrating common Android development patterns — Single Activity + MVVM architecture, fragment navigation, authentication, CRUD operations, and a swappable Firebase backend (Cloud Firestore or Realtime Database).

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📋 Table of Contents

• Features
• Tech Stack
• Project Structure
• Getting Started
• Architecture
• Screen Flow
• Adding a New Screen
• Switching the Database Backend
• License

✨ Features

Feature	Description
🔐 Authentication	Register and log in; the session is kept in SharedPreferences
👤 User Profile	View and edit your profile; admins can view and edit any user
🛒 Carts	Build a cart from food items, view your carts and their details
🍕 Food Management	Add food items with a name, price, and photo
🛡️ Admin Panel	Browse all users, all food items, and all carts
📷 Images	Camera / gallery picker; images stored as base64 (WEBP)
☁️ Cloud Database	Cloud Firestore (default) or Firebase Realtime Database

🛠️ Tech Stack

Technology	Details
Language	Java 17
Compile / Min / Target SDK	35 (Android 15)
Build System	Gradle 9.8.2, Android Gradle Plugin 8.10.1
Architecture	Single Activity, MVVM (AndroidX ViewModel + LiveData)
UI	AndroidX Fragment 1.9.1, RecyclerView 1.4.0, Material Components 1.12.0
Database	Firebase BoM 33.9.0 — Cloud Firestore & Realtime Database
Serialization	Gson 2.11.0 (stores the logged-in user locally)

📁 Project Structure

app/src/main/java/com/example/testapp/
│
├── MainActivity.java      # The only Activity — hosts every screen, implements NavigationHost
├── 📂 core/               # BaseFragment, NavigationHost, ViewModelFactory
├── 📂 screens/            # One folder per screen: <Name>Fragment + <Name>ViewModel
├── 📂 models/             # Data entities: User, Food, Cart (+ Identifiable)
├── 📂 services/           # Data-access interfaces + DatabaseService backend switcher
│   └── 📂 impl/
│       ├── 📂 firestore/  # Cloud Firestore implementations (default)
│       └── 📂 rtdb/       # Realtime Database implementations
├── 📂 adapters/           # RecyclerView / list adapters
└── 📂 utils/              # Validator, ImageUtil, SharedPreferencesUtil

Each folder has its own README.md with details.

🚀 Getting Started

Prerequisites

• Android Studio (recent stable release)
• JDK 17+ to run Gradle
• A Firebase project with Cloud Firestore enabled (and/or Realtime Database)
• An emulator or device running Android 15 (API 35) or newer

Installation

# 1. Clone the repository
git clone https://github.com/gilyerm/TestApp.git

# 2. Open the project in Android Studio

# 3. Put your google-services.json in the app/ directory

# 4. Sync Gradle, then run on an emulator/device (API 35+)

Build from the command line:

./gradlew assembleDebug        # build the debug APK
./gradlew testDebugUnitTest    # run unit tests

Note

google-services.json is not in the repository. Create your own Firebase project and download the file from the Firebase Console.

🏗️ Architecture

The app uses a Single Activity Architecture with MVVM. MainActivity is the only Activity; every screen is a Fragment with its own ViewModel.

┌──────────────────────────────────────────────┐
│  MainActivity  (implements NavigationHost)   │  ← toolbar + fragment container
├──────────────────────────────────────────────┤
│  screens/<name>/<Name>Fragment               │  ← View: renders UI, observes LiveData
│  screens/<name>/<Name>ViewModel              │  ← state + logic, exposes LiveData
├──────────────────────────────────────────────┤
│  core/ViewModelFactory                       │  ← injects IDatabaseService into ViewModels
├──────────────────────────────────────────────┤
│  services/  IDatabaseService → IUser/IFood/ICartService
│  services/impl/firestore  |  services/impl/rtdb
├──────────────────────────────────────────────┤
│  models/  User · Food · Cart                 │  ← plain Java objects (Identifiable)
└──────────────────────────────────────────────┘

Layer	Responsibility
MainActivity	Hosts fragments, owns the toolbar, implements NavigationHost (navigateTo, goBack, title, back button)
core	BaseFragment (gets the NavigationHost, sets title/back button), ViewModelFactory (dependency injection)
screens	Fragment = View, ViewModel = state and calls to services
services	Async CRUD interfaces with callbacks; Firestore and Realtime DB implementations
models	Entities stored in the database
adapters	Display lists of carts, foods, users, and image-source options
utils	Input validation, image conversion/permissions, local session storage

Data flow: Fragment calls a ViewModel method → ViewModel calls a service with a DatabaseCallback → callback updates MutableLiveData → Fragment's observer updates the UI.

🗺️ Screen Flow

Splash ──(logged in)──────────────────────────► Dashboard
   │                                              │
   └──(not logged in)──► Landing                  ├─► Add Food
                          ├─► Login ──────────────┤
                          └─► Register ───────────┤
                                                  ├─► Add Cart
                                                  ├─► My Carts ──► Cart Details
                                                  ├─► User Profile ──(sign out)──► Landing
                                                  └─► Admin (admins only)
                                                        ├─► Users List ──► User Profile
                                                        ├─► Food Items
                                                        └─► All Carts ──► Cart Details

➕ Adding a New Screen

1. Create screens/<name>/ with <Name>Fragment and <Name>ViewModel.
2. Make the ViewModel extend ViewModel and take one constructor argument: IDatabaseService.
3. Make the Fragment extend BaseFragment, implement getTitle(), and override shouldShowBackButton() if it is a root screen.
4. Get the ViewModel with new ViewModelProvider(this, new ViewModelFactory()).get(<Name>ViewModel.class).
5. Add a layout res/layout/fragment_<name>.xml.
6. Open it from another screen with navigationHost.navigateTo(new <Name>Fragment(), true).

No manifest change is needed — only MainActivity is declared.

🔀 Switching the Database Backend

Cloud Firestore is the default. To use Realtime Database, call this before anything uses the database (for example at the start of MainActivity.onCreate):

DatabaseService.setBackend(DatabaseService.DatabaseBackend.REALTIME_DATABASE);

Both backends use the same paths/collections: users, foods, carts.

📄 License

This project is licensed under the MIT License — see the LICENSE file for details.

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Made with ❤️ by Gilyerm