FitISO

A local-first, single-user workout tracker built with .NET MAUI.

About the name

FitISO = Fitness + ISOlation. It's a local-only app, no accounts, no cloud sync, no server - just you and a SQLite file on your phone. Single user, isolated data, hence the name.

The logo is a bird holding a dumbbell because it's also a wordplay with Fitis, the Iberian name for the Willow Warbler. That's it, that's the whole joke.

Congrats, you just read a whole paragraph about a bird. Anyway, here's what the app actually does:

Features

• Active workout tracking - a persistent live timer, editable weight/reps per set with debounced autosave, and swipe gestures to quickly add or remove sets from an exercise.
• Set completion progress - a thin progress bar in the title bar fills up as you complete sets (weight + reps both entered) during the active workout, giving an always-visible sense of how far along you are without eating into scroll space.
• Personal records & history at a glance - each exercise card surfaces your best-ever set and your most recent sets for quick comparison while you train.
• Exercise library - browse, search, add, and inspect exercises via dedicated popups.
• Workout templates - save and reuse workout structures instead of building them from scratch every time.
• Workout history - review past completed workouts, with one-tap PDF export for sharing and a monthly calendar heatmap showing which days you trained. Step month-by-month, swipe left/right or jump straight to your first workout month or back to the present.
• Rest stopwatch - an optional rest stopwatch during active workouts that auto-starts the moment a set is marked complete (weight + reps both entered), survives app restarts/kills via persisted state and can optionally chain into the next exercise's first set instead of stopping when you finish the last set of an exercise. Toggle it from Settings.
• Custom tab bar - a shaped bottom navigation bar (via Nalu.Maui) with a context-sensitive action button (e.g. "add exercise" while a workout is active).
• Accent themes - switch the app's accent palette from Settings.
• Backup & restore - export the SQLite database to a .db3 file from Settings, and import a backup back in later.
• Auto backup - optionally back up the database automatically to your phone's Downloads folder every time you finish a workout.
• Home screen widgets (Android) - favourite exercise best set, favourite exercise history chart, favourite workout quick-start, days since last workout, last workout summary and monthly workout heatmap.
• App shortcuts (Android) - long-press the app icon to quickly jump to your favourite workout or your workout history.

Tech stack

Project (layer)	Responsibility	Technologies
FitISO.Data	Persistence	Entity Framework Core 10, SQLite
FitISO.Services	Business logic	Plain C#, depends only on FitISO.Data
FitISO.Maui	Presentation	.NET MAUI (net10.0 — Android, iOS, Mac Catalyst, Windows), CommunityToolkit.Mvvm (ObservableObject, [RelayCommand], [ObservableProperty], WeakReferenceMessenger), CommunityToolkit.Maui (toasts, Expander, etc.), Nalu.Maui (Nalu.Maui.Navigation & Nalu.Maui.Layouts)
FitISO.Tests	Testing	NUnit, Microsoft.EntityFrameworkCore.InMemory

Architecture

The solution is split into four projects, layered so the UI depends on services and services depend on data - never the reverse:

FitISO.Data/            EF Core DbContext, entity models and migrations.
FitISO.Services/        Business logic sitting between the UI and the database. Depends only on FitISO.Data.
FitISO.Maui/            The MAUI app itself:
  ├─ Models/             UI-facing observable wrappers around the FitISO.Data entities.
  ├─ ViewModels/         One view model per page/popup, using CommunityToolkit.Mvvm.
  ├─ Views/              XAML pages and popups.
  ├─ Rendering/          Imperative SkiaSharp canvas-drawing code, invoked from code-behind.
  ├─ Messages/           WeakReferenceMessenger message types for cross-view-model communication.
  ├─ Services/           MAUI-layer application services (settings, backup, widget state) — see note below.
  ├─ Converters/         Value converters for XAML bindings.
  ├─ Resources/          Styles, accent-theme resource dictionaries, fonts, images.
  └─ Platforms/          Per-platform entry points and platform-specific code.
FitISO.Tests/           NUnit tests for the service layer, backed by EF Core's in-memory provider.

Two pairs of names are easy to mix up across layers:

• FitISO.Maui.Models vs FitISO.Data.Models - the Data models are plain EF entities, while the Maui models are ObservableObject - based wrappers that add change notification, debounced autosave and null-coercion needed for live-editable UI, without polluting the persistence layer with UI concerns.
• FitISO.Services (the project) vs FitISO.Maui/Services (the folder) - the former is plain C# with zero MAUI/platform dependencies and is what's covered by FitISO.Tests; the latter is MAUI-side glue that talks to Preferences, the file system, or Android widget APIs (e.g. WorkoutSettingsService, AutoBackupService, MonthlyHeatmapService), and generally wraps or coordinates calls into the former rather than duplicating its logic.