May 29, 2018
May 4, 2021 (Retired)
Sysdata S.p.A. (SysdataSpA)
Andrea Guitto (aguitto)
sranieri53 (sranieri)
Fabio Sassu (fabiosassu-sysdata)
Vincenzo Sarnataro (vincenzosarnataro)
Source code


A Kotlin android architecture with Google Architecture Components

1. A Brief Introduciton

The app is a sample project that shows how to implement the KTAndroidArchitecture into your Android app.

1.1 What is KTAndroidArchitecture?

It is a layer-based architecture that allows a real decoupling of the UI components from the business logic.

The main components are:

Here you can find a list of guides depending on your implementations :

2. How to use it?

2.1 Import dependency

2.1.1 in Project level build.gradle add this repository

   maven { url  'https://dl.bintray.com/sysdata/maven' }

2.1.2 in your App level build.gradle add this dependecy

    implementation 'it.sysdata.mobile:ktandroidarchitecturecore:1.0.3'

2.1.3 import the settings for use live template and file template

2.2 Create a Repository

A repository just needs to extend BaseRepository in this way

  class AuthRepository:BaseRepository() 

2.3 Create a UseCase

A usecase has to extend UseCase<Out,In> and implement a the "run" method:

class LoginUseCase: UseCase<UserLogged, LoginActionParams>() {
    override suspend fun run(params: LoginActionParams): Either<Failure, UserLogged> {
        do something
        return result

or you can just create a new usecase by going to File Template New->Kotlin Use Case

The "run" function defined inside the UseCase can return a Failure object or a Model object.

The input params are defined in a Param object which is a data class defined like this

data class LoginActionParams(val email: String, val password: String) : ActionParams()

2.4 Create a ViewModel for your Activity/Fragment

A ViewModel needs to extend the abstract class BaseViewModel

class LoginViewModel: BaseViewModel()

2.4.1 Define an Action inside the ViewModel

An Action can be created by using a Builder like this

val actionLogin = Action.Builder<ActionParams,Model,UiModel>()
            .buildWithUiModel { UiModel(it) }

or you can just use the live template ac to create a usecase straight from the class!

The flow is composed by the following steps:

  1. The execution of an Action performed by the method execute(...) of Action class.
  2. The first logical step is the post of an object inside an internal livedata called LoadingLiveData indicating that loading has started. The UI can observe this LiveData using the method observeLoadingStatus(...).
  3. The next step is the execution of a usecase which uses repositories to retrieve some data.
  4. The result of repositories' call is returned to the usecase.
  5. The post of an object inside an internal livedata called LoadingLivedata indicating that loading has finished. The UI can observe this LiveData using the method observeLoadingStatus(...)
  6. the post of the usecase result in two internal livedatas based on the success or the failure; the UI can observe these two LiveDatas by using observe(...) and observeFailure(...)

2.5 Call the Action from the Activity/Fragment

An action has several methods like:

  • action.observe(...), this method observes the success of the operation defined inside the usecase;
  • action.observeFailure(...), this method observes the failure of the operation;
  • action.observeLoadingStatus(...), this method observes the loading state of the operation;
  • action.execute(...), this method calls the "run" function inside the usecase and executes the operation;
  • action.safeExecute(...), this method calls the "run" function inside the usecase and executes the operation into in a SafeExecuteInterface;

2.6 Custom safe executor

The safeExecute() method call is meant to be used if you plan a different behaviour based on the error of your response. If you use the simple execute() call, whenever there's an error, the method will throw an exception and you will have to handle it by try-catching it and defining a behaviour for that UseCase. If you use the safeExecute() method call, whenever there's an error, it will fallback to an InternalError failure in case of an exception, saving you from an application crash. Moreover, if you'd like to customize the behaviour in a general way, you can define a class that extends from the SafeExecuteInterface and inside the overridden safeExecute() call you can define the custom behaviour you want for your application. Finally, you'll have to assign the custom SafeExecutor as the BaseConfig.safeExecutor variable.

        BaseConfig.safeExecutor = MySafeExecutor() 

It is suggested that you assign this variable as soon as possible (i.e. in the Application's class onCreate() method).

To call an action you have to write this:

        viewModel.action.observe(this, ::onActionSuccess)
        viewModel.action.observeFailure(this, ::onActionFailed)

3 KTAndroidArchitecture main components

3.1 UI

The UI layer of the architecture includes Activities, Fragments and Views.

3.2 UIModel

A UIModel is an object that contains all UI-related datas of a view, fragment or activity.

Read More

3.3 ViewModels with Livedata

Each activity or fragment could have a ViewModel which is an object designed to store and manage UI-related data in a lifecycle aware way by defining some Actions to call one or more UseCases

3.4 UseCase

A UseCase is a wrapper for a small business logic operation. A UseCase can use one or more Repository to retrieve or to set data, then it returns the response event.

Read More

3.5 Repository

A Repository handles the process of saving or retrieving data from a datasource, it is managed by one or more UseCase.

Read More

3.6 Action

An Action handles the process of calling a UseCase and map the response. Usually, an action uses only one UseCase, but it is possible to define an ActionQueue in order to call multiple UseCases sequentially. Into an ActionQueue each UseCase, except the first, takes the result of the previous as parameters and gives the output to the next one.


val actionLogin = Action.Builder<ActionParams,Model,UiModel>()
            .buildWithUiModel { UiModel(it) }


val actionQueue = ActionQueue.Builder<LoginActionParams, UserLogged>()

or just acq command live template

Optionally, you can add a CoroutineScope to the action.

actionLogin.execute(LoginActionParams(username, password), viewModelScope)

For more informations about the CoroutineScope, please refer to this articles :

3.7 Testing

3.7.1 InstrumentedTests

It is possible to perform instrumented tests on the architecture. To learn more about instrumented tests, please, refer to the following section: Instrumented Tests

3.7.2 Unit test

It is possible to perform unit tests on the architecture. To learn more about unit tests, please, refer to the following section: Unit tests



  • added safeExecute.


  • Added Scope to actions.


  • fixed abnormal behavior on ActionQueue.
  • Added the possibility to add the action instance instead of the class. This is useful for dependency injection (i.e. Dagger).
  • Added ActionSingle.
  • fixed the behavior of the error post in the observeFailure function.
  • Updated Gradle plugin version.


  Copyright (C) 2020 Sysdata S.p.A.

  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


  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  See the License for the specific language governing permissions and
  limitations under the License.