A currency tracker app demonstration. It refreshes currency list every single second based on the main currency. In addition to that, main currency is selectable.
Libbra is a sample app that allows to track currency exchanges. This app presents modern approach to Android application development using Kotlin and latest tech-stack.
This project is a hiring task by Revolut. The goal of the project is to demonstrate best practices, provide a set of guidelines, and present modern Android application architecture that is modular, scalable, maintainable and testable. This application may look simple, but it has all of these small details that will set the rock-solid foundation of the larger app suitable for bigger teams and long application lifecycle management.
First off, you require the latest Android Studio 3.6.0 (or newer) to be able to build the app.
Moreover, to sign your app for release, please refer to keystore.properties
to find required fields.
# Signing Config
signing.store.password=<look>
signing.key.password=<look>
signing.key.alias=<look>
signing.store.file=<look>
To maintain the style and quality of the code, are used the bellow static analysis tools. All of them use properly configuration and you find them in the project root directory .{toolName}
.
Tools | Config file | Check command | Fix command |
---|---|---|---|
detekt | default-detekt-config | ./gradlew detekt |
- |
ktlint | - | ./gradlew ktlintCheck |
./gradlew ktlintFormat |
spotless | /spotless | ./gradlew spotlessCheck |
./gradlew spotlessApply |
lint | /.lint | ./gradlew lint |
- |
All these tools are integrated in pre-commit git hook, in order ensure that all static analysis and tests passes before you can commit your changes. To skip them for specific commit add this option at your git command:
git commit --no-verify
The pre-commit git hooks have exactly the same checks as Github Actions and are defined in this script. This step ensures that all commits comply with the established rules. However the continuous integration will ultimately be validated that the changes are correct.
App support different screen sizes and the content has been adapted to fit for mobile devices and tablets. To do that, it has been created a flexible layout using one or more of the following concepts:
In terms of design has been followed recommendations android material design comprehensive guide for visual, motion, and interaction design across platforms and devices. Granting the project in this way a great user experience (UX) and user interface (UI). For more info about UX best practices visit link.
Moreover, has been implemented support for dark theme with the following benefits:
Page | Light Mode | Dark Mode |
---|---|---|
Currency |
The architecture of the application is based, apply and strictly complies with each of the following 5 points:
Modules are collection of source files and build settings that allow you to divide a project into discrete units of functionality. In this case apart from dividing by functionality/responsibility, existing the following dependence between them:
The above graph shows the app modularisation:
:app
depends on :rules
.:rules
depends on nothing.The :app
module is an com.android.application, which is needed to create the app bundle. It is also responsible for initiating the dependency graph and another project global libraries, differentiating especially between different app environments.
The :rules
module is an com.android.library, basically contains lint checks for the entire project.
Ideally, ViewModels shouldn’t know anything about Android. This improves testability, leak safety and modularity. ViewModels have different scopes than activities or fragments. While a ViewModel is alive and running, an activity can be in any of its lifecycle states. Activities and fragments can be destroyed and created again while the ViewModel is unaware.
Passing a reference of the View (activity or fragment) to the ViewModel is a serious risk. Lets assume the ViewModel requests data from the network and the data comes back some time later. At that moment, the View reference might be destroyed or might be an old activity that is no longer visible, generating a memory leak and, possibly, a crash.
The communication between the different layers follow the above diagram using the reactive paradigm, observing changes on components without need of callbacks avoiding leaks and edge cases related with them.
This project takes advantage of many popular libraries, plugins and tools of the Android ecosystem. Most of the libraries are in the stable version, unless there is a good reason to use non-stable dependency.
Nuh Koca
Copyright 2020 Nuh Koca
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.