News Feed (Android Paging 3 sample)

A small Android app that shows an endlessly scrolling list of sports news, built to demonstrate the Paging 3 library with a clean, testable structure.

Originally written as a companion to the article Android Paging Library Step-By-Step Implementation Guide. The code has since moved to Paging 3 and coroutines, so it no longer matches the article's Paging 2 / RxJava code.

Features

• Infinite scrolling with page loading, a footer spinner and a footer retry
• Pull to refresh
• Loading, empty and error states with retry
• Light and dark theme (Material 3), edge-to-edge layout

Tech stack

Kotlin, Paging 3, Coroutines and Flow, ViewModel, Retrofit and Gson, Coil, Material 3, View Binding.

Project structure

data/remote   Retrofit API, DTOs and DTO to domain mapping
data/paging   PagingSource (page loading and error handling)
data          NewsRepository (builds the Pager)
domain        News model
di            AppContainer (manual dependency injection)
ui/news       Activity, ViewModel, PagingDataAdapter, load state footer

Modifying items

PagingDataAdapter has no add, update or remove methods. Items come from PagingData, which is immutable, so change the data instead:

• Transform the stream in the ViewModel with PagingData.map, filter or insertSeparators. Keep the edits (for example removed ids) in a StateFlow and combine it with the Pager flow, so the list is rebuilt when they change.
• For persistent edits, use a single source of truth such as Room with a RemoteMediator. Write the change to the database and the PagingSource invalidates and reloads on its own.
• Call adapter.refresh() to reload the list from the first page.

Run

Requires Android Studio with JDK 21 and Android SDK 37.

./gradlew assembleDebug        # build
./gradlew testDebugUnitTest    # unit tests
./gradlew lintDebug            # lint

Tests

Unit tests cover the DTO mapper, NewsPagingSource (paging keys, end of list, errors), the API parsing (with MockWebServer) and NewsListViewModel.