Classifieds App

Functionality

The app's functionality includes:

1. Fetch a list of products form a remote api & show them in RecyclerView.
2. When an item is selected from RecyclerView it will load the item detials in Detail Screen.
3. The app uses a custom image_cache_lib to cache images. The library support DISK_CACHE and MEMORY_CACHE.
4. On first load the app saves the products in a local database & on subsequent load - the items are loaded from local DB.
5. The app supports SwipeRefreshLayout to pull to refresh RecyclerView content from Remote source.

Architecture

The app uses clean architecture with MVVM(Model View View Model) design pattern. MVVM provides better separation of concern, easier testing, Live data & lifecycle awareness, etc.

UI

The UI consists of two screen

1. MainActivity.kt - Initial screen. Shows list of products.
2. DetailActivity.java - Shows detail data about a product item.

Model

Model is generated from JSON data into a Kotlin data class. In addition entity class has been added for room database along with Type converter for saving/retrieving custom object data.

ViewModel

MainViewModel.kt

Used for fetching product listing & update livedata. Also send out the status of the network call like Loading, Success, Error using sealed class.

DetailViewModel.kt

Used for converting & checking detail data.

Dependency Injection

The app uses Dagger-hilt as a dependency injection library.

The ApplicationModule.kt class provides Singleton reference for Retrofit, OkHttpClient, Repository etc.

Network

The network layer is composed of Repository, ApiService. ListingApi - Is an interface containing the suspend functions for retrofit API call.

ListingRepository - Holds the definition of the remote/local repository call.

Building

You can open the project in Android studio and press run. Android Studio version used to build the project: Arctic fox 2020.3.1

Gradle plugin used in the project will require Java 11.0 to run.

you can set the gradle jdk in Preferences->Build Tools->Gradle->Gradle JDK

Libraries used

1. Android appcompat, core, constraint layout, Material Support.
2. Android View Binding
3. Hilt for dependency injection
4. Retrofit for REST API communication
5. Coroutine for Network call
6. Lifecycle, ViewModel
7. LiveData
8. Room for local database.
9. image_cache_lib for image caching & loading.
10. Swipe Refresh Layout for pull-to-refresh RecyclerView.
11. Mockito & Junit for Unit testing.
12. Robolectric for Instrumentation testing
13. Truth for Assertion in testing.
14. Espresso for UI testing.

Testing

Unit and integration testing has been added for MainViewModel , DetailViewModel, ListingRepository & ResultPercelableTest.

MainViewModelTest.kt

Test the viewmodel of the app using CoroutineRule & LiveData Observer.

The test cases comprise of testing different states like Loading, Success, Error with fake data for testing listing response.

ListingRepository.kt

Test the Repository of the app using Robolectric.

The test comprises of testing the functionality of Product Room Database like Insertion, Remove, Get saved listings etc.

Mock Webserver is used to test the Network api response in case of successful data, empty, failed case.

UI testing has been added for MainActivity & DetialActivity using Espresso.

Screenshots

Initial Screen	Detail Screen