PatternKit — MVP (XML Views)

Part of PatternKit, a side-by-side reference codebase where the same small Tasks CRUD app is implemented once per architecture pattern across iOS and Android. Every module ships identical behaviour — the same domain model, the same three screens, the same mock data layer — so the only thing that varies is the architecture itself.

This module is the MVP (Model–View–Presenter) flavour on the traditional XML view stack — MVP's natural Android home. It's a purist take: each Fragment is a passive view that implements a Contract.View interface, and the Presenter drives it through that interface. The Fragment forwards user actions to the presenter and renders whatever the presenter pushes; it holds no presentation logic.

Why purist? PatternKit already has MVVM, MVVM+Clean, and MVI modules. MVP is here as a faithful reference. Notice the classic Android MVP weakness it makes visible: the Presenter is a plain object (not a ViewModel), so it doesn't survive a configuration change — the Fragment recreates it and the screen reloads on resume. That fragility is exactly why ViewModel/MVVM won on Android, and seeing it is the point. The Compose sibling (PatternKitAndroidMvpCompose) shows the same contract deliberately against the grain of a declarative UI.

Stack

• Language: Kotlin
• UI: XML layouts + ViewBinding · Fragments · RecyclerView
• Architecture: MVP — passive Fragments behind Contract.View interfaces, presenters own all logic
• Async: the presenter owns a CoroutineScope (cancelled on detach)
• Navigation: in the Fragments, on the presenter's command (Contract.View routing methods)
• DI: Dagger 2 (KSP) — AppComponent exposes the repository; presenters are built per view lifecycle
• Min SDK: 28 · Target/Compile SDK: 36
• Package: com.preetanshumishra.patternkit.android.mvpxml

The Tasks feature

A single-user task list. One entity (TaskItem: title, optional notes, optional due date, priority, completion). Three screens: List (filter / sort / swipe-delete / add), Detail (toggle / edit / delete), Form (create or edit, validation, mock async save). Data comes from MockTaskRepository — an in-memory store seeded with ~12 tasks, configurable latency + failure rate.

The MVP shape

• View (passive) — a Fragment implementing …Contract.View. It exposes render(state) / seed(…) / setSaveEnabled(…) / showError(…) and navigation commands (showDetail, showCreate, showEdit, close), forwards user actions to the presenter, and does nothing else.
• Presenter — a plain class owning the presentation logic, the repository (plain MVP — no domain layer), and a CoroutineScope. Holds the view via the Contract interface; navigation is a presenter decision the Fragment carries out.
• Model — TaskItem + the TaskRepository, the shared source of truth; screens reload on resume so edits elsewhere are reflected.

Project layout

app/src/main/
├── kotlin/.../mvpxml/
│   ├── data/          # MockTaskRepository, TaskRepository, seed data
│   ├── model/         # TaskItem, Priority, TaskFilter, TaskSort
│   ├── di/            # AppComponent, RepositoryModule
│   ├── presentation/  # TaskList/Detail/Form Contract + Presenter
│   ├── ui/
│   │   ├── list/      # TaskListFragment (passive) + TaskAdapter
│   │   ├── detail/    # TaskDetailFragment (passive)
│   │   ├── form/      # TaskFormFragment (passive)
│   │   ├── NavArgs.kt, MainActivity
│   └── PatternKitApp.kt
└── res/               # layouts, menus, nav_graph.xml

Build & run

./gradlew assembleDebug      # build the debug APK
./gradlew installDebug       # install on a connected device/emulator

Or open the project in Android Studio and run the app configuration.