Picsum-Photo-Browsing
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A sample photo browsing app in Kotlin, Android using Picsum image API.
Picsum Photo App
Functionality
The app's functionality includes:
- Fetch a list of images from picsum photos api (https://picsum.photos/) and show them in
RecyclerView
usingStaggeredGrid Layout Manager
. - User can view the list of images using smooth infinite scroll using paging api.
- When an image is selected from
RecyclerView
it will load the full-screen image with pinch zoom in/out feature. - User can download the image from full-screen view.
- User can share the image from full-screen view.
- The image list is cached into local DB, so the list of images are available offline.
- The app supports
SwipeRefreshLayout
to refreshRecyclerView
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
-
MainActivity.kt
- Initial screen. Shows a list of images. -
FullScreenActivity.kt
- Shows full-screen view of the image with additional options.
Model
Model is generated from JSON
data into a Kotlin data class.
In addition, entity class has been added for room database.
ViewModel
MainViewModel.kt
Used for fetching picsum images & update flow using paging data soruce.
FullScreenViewModel.kt
Used for downloading the image into a bitmap & save it into internal storage.
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.
PicsumApi
- Is an interface containing the suspend functions for retrofit API call.
ImageListRepository
- 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
Tech Stack
- Android appcompat, KTX, Constraint layout, Material Support.
- Android View Binding
- Hilt for dependency injection.
- Retrofit for REST API communication.
- Coroutine for Network call.
- Lifecycle, ViewModel
- Kotlin Flow
- Room for local database.
- Glide for image loading.
- Paging 3 with RemoteMediator for smooth infinite scroll.
- Custom fileprovider for writing & reading files into internal storage.
-
Swipe Refresh Layout for pull-to-refresh
RecyclerView
. - Mockito & Junit for Unit testing.
- Robolectric for Instrumentation testing.
- Truth for Assertion in testing.
- Photo View for zoom in/out image.
Testing
Unit and integration testing has been added for MainViewModel
, FullScreenViewModel
, ImageListRepository
& ImageListItemSerializableTest
.
MainViewModelTest.kt
Test the viewmodel of the app using CoroutineRule
.
The test cases comprise of testing different states like Loading, Success, Error with fake data for testing image list response, cache response.
FullScreenViewModelTest.kt
Test Image donwload returns file uri & URL to bitmap conversion.
ListingRepository.kt
Test the Repository of the app using Robolectric
.
The test comprises of testing the functionality of Image Room Database like Insertion, Remove, Get saved response etc.
Mock Webserver is used to test the Network api response in case of successful data, empty, failed case.
Screenshots
Infinite Scroll, Pinch Zoom | Image Download | Image share |
---|---|---|
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