uLesson App Assessment

Introduction

The application is written entirely in Kotlin.

It uses the single activity acrhitecture pattern which is the recommended way of building modern android apps and it's entirely structured with MVVM acrhitectire to ensure separation of concern and highly testable code.

With the help of giuide to architecture, we simply check if there's cached data, if there is, we display the cached data and we make a background network call to update the database, otherwise (if the cache is empty), we make a network call, save the response to the local database and the UI is updated accordingly.

Architecture

The app uses the dependency inversion rule to ensure separation of concerns and easy testing. It consists of a single activity and 3 fragments

Database structure

There are two tables in the database, subject and recentview

subject is used to persist the subjects

recentview is used to persist the recently watched topics

UI Structure

• DashboardFragment: This fragment displays the list of subjects and recently watched videos, using room as source of data.

• SubjectFragment: This fragment displays all the lessons of a particular subject clicked from the previous screen. It requires an argument(subjectId) to be passed by the previous screen in order to get the lessons of the subject clicked. No network call is made here, since the data is cached, we just query the room db to fetch the subject and update the UI accordingly.

• VideoPlayerFragment: This fragment plays the video of a lesson, underneath is a title and subtitle TextView that shows a static dummy text, this is used just to have a closer look to the UI. Something also worth noting is the ExoPlayer EventListener; when it receives the ExoPlayer.STATE_READY I assume that the video has been watched, I made this decision inorder not to wait for the video to be completed before saving it to the recentview table, I think this should typically be done in the ExoPlayer.STATE_ENDED

Also the recent watched videos is saved using the subjectId subjectName and chapterName as topicName, so for example if I watched Standard deviation lesson under a chapter called statistics in Mathemeatics subject, what would be saved in the recentview table is statistics as the topicName, Mathematics as the subjectName and it uses the subjectId as the unique key so that when you watch another lesson in another chapter of the same subject it updates the topic name as the most recently watched topic in that subject.

In other words, the recently watched videos is saved on a chapter level not an individual lesson.(Not sure if this is the best approach to that)

Libraries used

• Room: The Room persistence library provides an abstraction layer over SQLite to allow for more robust database access while harnessing the full power of SQLite.
• Navigation component: a library that manages and eases fragment transactions
• Hilt: for dependency injection
• LiveData: An observable data holder class consumed by the layout to display ui data
• ViewModel: a class that housed UI-related data
• Retrofit: for making network request
• Coroutine: recommended way to make execute asynchronous code, main safe!, and eliminates call back hell code
• Timber: used for logging
• Glide: a library for loading images
• Exoplayer : library used for playing videos

Figma link: https://www.figma.com/file/rfaVkZMsmdq69sioOSuvfN/Android-Interview-App?node-id=0%3A1

Clone project

Use Android Studio 4.0 and above

ToDo

• UI testing with espresso

License

MIT License

Copyright (c) 2020 Tobiloba Oyelekan

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The above copyright notice and this permission notice shall be included in all
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