PreLoved Market

A Second-Hand Fashion Marketplace for Campus Students

PreLoved Market is a mobile app that connects students within the campus community to buy and sell second-hand fashion items. It solves the problem of students relying on chance encounters with street hawkers, unreliable WhatsApp posts, and Instagram thrift pages — where sizing is uncertain, product visibility is poor, and there is no trust mechanism between buyers and sellers.

Team Information

Item	Details
Team Name	DevLink
Course	Mobile Application Development (MAD) — Level 3
University	University of Rwanda

Team Members & Contributions

• Asifiwe Afisa Uwitonze Project Lead, UI/UX Designer

  • Field research & user interview (Emmanuel)
  • DESIGN.md and Google Stitch mockups
  • Section A: Dart fundamentals (helpers.dart, dummy_data.dart)
  • Section B: Data models (BaseModel, Product, Searchable mixin, ProductService)
  • Section C: App theme, HomeScreen, ProductDetailScreen, custom widgets
  • Project setup (fonts, assets, pubspec configuration)
  • GitHub repository management

• Diane Uwamariya — Research Lead, Documentation Lead

  • Field research & user interview (Kaneza Devine)
  • Section B: Data models (User, Review, Rateable mixin)
  • Section D: Navigation setup (main.dart, named routes, data passing)
  • Section D: AddListingScreen form with validation
  • Video demo coordination

Problem Statement

Students at campus face significant challenges when buying and selling second-hand fashion items due to the lack of a centralized, reliable platform. Current methods — street hawkers, Instagram thrift pages, and WhatsApp groups — lead to trust issues, difficulty finding specific items, inability to verify size and fit, poor product visibility, and no quality assessment.

How to Run the App

Prerequisites

• Flutter SDK (3.7.0 or later)
• Android Studio or VS Code with Flutter extension
• Android emulator or physical device

Steps

# 1. Clone the repository
git clone https://github.com/Pelino-Courses/progressive-capstone-project-devlink.git
cd preloved_market

# 2. Install dependencies
flutter pub get

# 3. Verify your setup
flutter doctor

# 4. Run the app
flutter run

Flutter Doctor Screenshot

Repository Structure

preloved_market/
├── lib/
│   ├── main.dart                        # App entry point + named routes (D1)
│   ├── theme/
│   │   └── app_theme.dart               # Material Design 3 theme from DESIGN.md (C4)
│   ├── models/
│   │   ├── base_model.dart              # Abstract base class (B3)
│   │   ├── product.dart                 # Product model with Searchable mixin (B1, B2)
│   │   ├── user.dart                    # User model with Rateable mixin (B1, B2)
│   │   ├── review.dart                  # Review model (B1, B2)
│   │   └── enums.dart                   # ProductCategory, ProductCondition enums
│   ├── mixins/
│   │   ├── searchable.dart              # Search functionality mixin (B3)
│   │   └── rateable.dart                # Rating calculation mixin (B3)
│   ├── services/
│   │   └── product_service.dart         # Async data service with Future.delayed (B5)
│   ├── data/
│   │   └── dummy_data.dart              # Sample data with List, Map, Set (A3)
│   ├── utils/
│   │   └── helpers.dart                 # Dart fundamentals demo (A1-A4)
│   ├── widgets/
│   │   └── product_card.dart            # Reusable ProductCard + ConditionBadge (C3)
│   └── screens/
│       ├── home_screen.dart             # Home screen with product grid (C1, C2)
│       ├── product_detail_screen.dart   # Product detail with seller info (C2, D2)
│       └── add_listing_screen.dart      # Listing form with validation (D3, D4)
├── assets/
│   └── images/                          # Product images
├── fonts/
│   ├── Poppins-Regular.ttf
│   ├── Poppins-Medium.ttf
│   ├── Poppins-SemiBold.ttf
│   └── Poppins-Bold.ttf
├── design/
│   ├── 01_home_screen.png               # Stitch mockup: Home
│   ├── 02_detail_screen.png             # Stitch mockup: Product Detail
│   └── 03_form_screen.png               # Stitch mockup: Add Listing Form
├── docs/
│   ├── field_research.md                # Field research from progressive project
│   ├── app_concept.md                   # App concept document
│   └── team_charter.md                  # Team charter and roadmap
├── wireframes/                          # Original wireframe sketches
├── DESIGN.md                            # Design system: colors, typography, rationale
├── pubspec.yaml
└── README.md

Mini-Capstone Snapshot — Parts A–D

This section summarizes what was added for the Mini-Capstone submission.

Section A — Dart Fundamentals

• A1: Variables with final, const, var; null-safe types using ?, !, ?? (helpers.dart, product.dart, user.dart)
• A2: Functions with named parameters, optional parameters, and arrow syntax (helpers.dart, rateable.dart)
• A3: List, Map, and Set used in real app data structures (dummy_data.dart)
• A4: Control flow with if/else, switch expressions, ternary operators (helpers.dart, product.dart)

Section B — OOP & Data Models

• B1: 3 domain model classes: Product, User, Review
• B2: All models extend abstract BaseModel class (inheritance)
• B3: Searchable mixin on Product, Rateable mixin on User, BaseModel abstract class
• B4: Constructors with named parameters, required, and default values
• B5: ProductService with async/await and Future.delayed for simulated data loading

Section C — Flutter UI & Widgets

• C1: Home screen displays realistic product data in a two-column grid
• C2: Layout widgets: Column, Row, Stack, ListView.builder, GridView.builder
• C3: Custom reusable ProductCard and ConditionBadge widgets used across multiple screens
• C4: Material Design 3 theme with ColorScheme mapped from DESIGN.md, Poppins TextTheme

Section D — Navigation & Forms

• D1: 3 screens connected via named routes (/, /product-detail, /add-listing)
• D2: Product object passed from HomeScreen to ProductDetailScreen via route arguments
• D3: Form with GlobalKey<FormState>, TextFormField validators, form.validate() on submit
• D4: 7 form fields with meaningful validation (length, format, range, pattern checks)
• D5: Back navigation with Navigator.pop works correctly on all screens

Phase 0 — Design Mockups

• 3 Google Stitch mockups in /design/ folder
• DESIGN.md with full colour palette (hex codes), typography, component styles, and design rationale

Design System Summary

Role	Colour	Hex Code
Primary	Forest Green	#2D6A4F
Primary Container	Soft Sage	#B7E4C7
Secondary	Warm Terracotta	#C17754
Background	Warm Linen	#FDF6EC
Surface	Off White	#FFFFFF
On Background	Charcoal Brown	#2C2C2C
Error	Warm Red	#C0392B

Font: Poppins (Regular 400, Medium 500, SemiBold 600, Bold 700)

Full design system details are in DESIGN.md.

MVP Features

#	Feature	Friction Addressed
1	Product Listings with Details	Poor visibility, no quality assessment
2	Search & Filter	No centralized platform, can't find items
3	Seller Ratings & Reviews	Trust issues, quality assessment
4	In-App Chat	Size/fit verification
5	Size Guide & Measurements	Size/fit verification

Technologies Used

Technology	Purpose
Flutter	Cross-platform mobile app framework
Dart	Programming language
Material Design 3	UI component system and theming
Google Stitch	AI-powered design mockup generation
GitHub	Version control and collaboration

Video Demo

YouTube Link: https://youtu.be/m-o-ZCRqgdw

Video Title Format: [MAD] Mini-Capstone Parts A-D — PreLoved Market — Asifiwe Afisa Uwitonze & Diane Uwamariya

Submission Details

Item	Value
Git Tag	mini-capstone-part-a-d
Commit SHA	(run git rev-parse HEAD after final commit)
Repository	(your GitHub URL)

AI Tools Acknowledgement

AI tools (Claude) were used to assist with:

• Document structuring and formatting
• Code scaffolding and architecture guidance
• Design system documentation

All core ideas, research, user interviews, and design decisions are original work by the team. Every team member can explain all code in their assigned sections.