Awesome

Talko

A sample messaging UI app for Android writen in Kotlin with a working local persistence layer.

Working

Video demo can be seen here

Running

You will need a device with API 27+ to run the Instant app.

Architecture

• MVVM with Observable pattern
• A modular app with Instant Apps

Decisions

• Room vs Realm vs ObjectBox - We needed a performant relational database that performed well with ReactiveExtensions. In the above combination, Room performs the best.
• Too many delegates? - We have created a delegate each for sender name, message, attachment and the same for recievers. This is done to make use of the recycling capabilities of RecyclerView and to be able to easily add functionality to a particular item.
• Rx vs Coroutines - Rx worked well for us to create a stream a data to be passed from our local storage, manipulate it and pass it to our UI.
• Adapter delegate vs Epoxy vs Groupie - Adapter Delegates works with ListAdapter and performs diffing of our lists on a background thread giving us optimum performance.
• Why not use Jetpack's Pagination library? - As the messages are supposed to be pulled out in a paginated manner, my first thought was to use the Pagination library with Room. This quickly became complex, as the library supports a single model from the Query. This would have led to a very complex query for Room. It would have still required some logic to be moved to the adapter to handle the receiver name element and deletion logic. Hence I decided to build my own pagination logic and keep majority of it in the viewmodel for easier testing.

Contains

• Dagger 2: Dependency injection
• Reactive streams: Networking, Local persistance, Stream manipulation & Async.
• LiveData and ViewModel: Isolate business logic and maintain state.
• Room: Local persistance
• Adapter Delegates: For easier multi-view RecyclerView with DiffUtils.

To-do

• Add test cases : Combination of UI and integration tests from karntrehan/Starwars and karntrehan/Posts

Licence

MIT License

Copyright (c) 2019 Karan Trehan

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.