FX App

FX App is a Jetpack-powered, MVVM Kotlin Single-Activity Android application that allows the calculate the current FX rate for two currency values as well as view through graphs, the past thirty-day history for FX Market API's default currency pairs - EURUSD, GBPUSD, and USDJPY as well as a paged list of the same historical data.

Pre-requisites

Before running app, you will need to acquire a FX Market API key from https://fxmarketapi.com/ and add this to the gradle.properties file:

FxMarketApiKey=""

Without this key, the app will output errors as it will not be able to connect to FX Market API and retrieve the historical data as well as the current FX rate when requested from the converter screen.

Things to note

The FX APP uses WorkManager to schedule two tasks and these are setup on app load:

• The list of currency pairs supported by FX Market API. These are cached into the Room database and retrieved for the dropdowns displayed on the converter screen

• The request for this project was to use the endpoint https://fxmarketapi.com/apihistorical. This endpoint does not support date ranges but only a single date at a time. Because of this to get historical data for the past thirty days, thirty separate requests are performed by the RefreshHistoryWorker, and on app load this is noticeable.

• Paging 3 is used on the graph screen below the graphs to display all the historical data retrieved from FX Market API and cached for the default currencies.

• The Android GraphView library https://github.com/jjoe64/GraphView used in this project has a significant impact on the UI especially in conjunction with Paging 3. This is noticeable most especially on emulator devices on the graph screen with delayed rendering.

Architecture

FX APP is built using Kotlin and the following Jetpack components:

• ViewModel & LiveData
• Navigation
• Paging 3
• SavedStateHandle with custom AbstractSavedStateViewModelFactory
• View Binding
• Data Binding
• Room
• WorkManager

and the following additional libraries:

• Hilt
• Retrofit & OkHttp
• Glide
• Material Design
• Android GraphView

Code and directory structure

> adapters
  |_ CommonBindingAdapter.kt
  |_ ConverterBindingAdapter.kt
  |_ GraphBindingAdapter.kt
> di
  |_ RepositoryModule.kt
  |_ RoomModule
> domain
  |_ Conversion
  |_ Currency
  |_ History
> network
  > models
    |_ NetworkConvertResponse.kt
    |_ NetworkCurrenciesResponse
    |_ NetworkHistoricalResponse
  |_ FXMarketConnectionInterceptor
  |_ FXMarketService.kt
> repository
  |_ FXAppRepository
  |_ HistoryPagingSource
> ui
  > converter
    |_ ConverterFragment
    |_ ConverterViewModel
  > graph
    |_ GraphFragment
    |_ GraphViewModel
    |_ HistoryLoadStateAdapter
    |_ HistoryPagingAdapter
> util
  |_ DateUtil
> work
  |_ RefreshCurrenciesWorker
  |_ RefreshHistoryWorker
|_ FxApplication
|_ MainActivity.kt

adapters

All the binding adapters for the search and result screen/section as well as for loading images via Glide

di

All the related Dependency Injection classes such as modules for the Hilt component

domain

Contained here are data classes whose attributes match the preference of the application as compared to what is received from the network.

network

The FX Market API connection service

network > models

The data classes modelled against the responses from FX Market API

repository

All data to the app originates from the repository. For FX APP, the repository performs the network call through the connection service and emits the data which the viewModels listen for. The repository makes use of a paging source HistoryPagingSource to deliver pages for the history on request.

work

All the current worker classes that will be run in the background by WorkManager

ui

All the screens in the app separated into - landing and detail - and their respective fragments and viewModels

FxApplication

@HiltAndroidApp annotated Application class

MainActivity

The entry point for the app and the container for the Navigation's NavHostFragment

Screenshots

License

MIT License

Copyright (c) 2021 Ahmed Tikiwa

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.