ImageLib

An Android image-loading library built from scratch (no Glide/Picasso/Coil) plus an example app that consumes it to display a grid of images fetched from a remote JSON list.

Modules

:imageloader   reusable image downloading & caching library (Kotlin, Java-friendly)
:app           example app - Android Views, MVVM + Clean Architecture, Coroutines

Library - :imageloader

Downloads, decodes (with downsampling), and caches images in two layers - an in-memory LruCache and a file-based disk cache - with a 4-hour TTL and manual invalidation. Built on Coroutines and HttpURLConnection, with no third-party dependencies. Fluent, Java-callable API:

ImageLoader.getInstance(context)
    .load(url)
    .placeholder(R.drawable.ic_placeholder)
    .error(R.drawable.ic_error)
    .into(imageView)

Full details, usage and architecture: imageloader/README.md.

Not yet released to Maven. The module is fully publish ready - maven-publish Is configured with coordinates com.example.imageloader:imageloader:1.0.0, sources & javadoc artifacts and POM metadata

But it is not pushed to a public repository yet!

The example :app consumes it directly via implementation(project(":imageloader")) you can also run ./gradlew :imageloader:publishToMavenLocal to install the AAR locally.

Example app - :app

A deliberately small but faithful slice of a full MVVM + Clean Architecture app - the same layering you'd use in production, scaled down to one screen:

ui (Views)         MainActivity + RecyclerView, ViewBinding, observes UiState
   │  StateFlow
presentation       MainViewModel (Hilt, viewModelScope) - no Android Context
   │  use cases
domain             ImageResource model, repository/cache interfaces, use cases
   │  interfaces
data               ImageApi (HttpURLConnection) + DTO + mapper,
                   ImageRepositoryImpl, ImageLoaderCacheManager
   │
di                 Hilt modules wiring interfaces → implementations

• Views, not Compose - RecyclerView (2-column grid) with ViewBinding.
• Each cell shows the loaded image (placeholder while loading) and its id.
• An Invalidate cache button clears the library cache on tap.
• The JSON list is fetched at runtime and parsed with org.json (no third-party JSON library); image loading is delegated to :imageloader.

The layering (domain interfaces, use cases, DI-injected ViewModel) is full-size; only the breadth - one screen, a couple of use cases - is compact.

Tech stack

• Language: Kotlin 2.0.21
• Async: Kotlin Coroutines + StateFlow
• UI: Android Views, ViewBinding, Material 3, RecyclerView, ConstraintLayout, SwipeRefreshLayout (no Jetpack Compose)
• Architecture: MVVM + Clean Architecture (domain / data / di layers)
• DI: Hilt 2.52 (+ KSP)
• Lifecycle: AndroidX Lifecycle ViewModel
• Networking / JSON: HttpURLConnection + org.json (no Retrofit/OkHttp/Gson)
• Image pipeline: the in-house :imageloader library
• Build: AGP 8.10.0, Gradle 8.11.1, version catalog · minSdk 24 · compileSdk 36
• Tests: JUnit4, kotlinx-coroutines-test

Build, run & test

./gradlew :app:assembleDebug                 # build the example app
./gradlew :imageloader:publishToMavenLocal   # publish the library AAR locally
./gradlew :imageloader:testDebugUnitTest :app:testDebugUnitTest

Unit tests cover the cache TTL and disk lifecycle, JSON parsing, and the repository DTO→domain mapping.