Architecture

This project is written in Kotlin. Uses concepts of Clean Architecture and Offline First.

MVVM is the default Design Pattern.

Kotlin Coroutines for Asynchronous Tasks.

Minimum Android SDK: API 21

+-------------------------------------+
|                                     |
|                 APP                 |
|                                     |
+-------------------------------------+
     |            |             |
     |            |             |
     v            v             v
+---------+  +---------+  +-----------+
|         |  |         |  |           |
|  AUTH   |  |  HOME   |  |  PROFILE  |
|         |  |         |  |           |
+---------+  +---------+  +-----------+
     |            |             |
     |            |             |
     v            v             v
+-------------------------------------+
|                                     |
|                 CORE                |
|                                     |
+-------------------------------------+

App Module: Splash Screen, Main Screen and Navigation Graphs. Knows all feature modules.
Auth Module: Auth Feature.
Home Module: Home Feature.
Profile Module: Profile Feature.
Core Module: Navigator, Navigation IDs, Custom Views, Datasources, Repositories. All core logic.

Libraries

Room for Database Implementation
Glide for Image Processing
Koin for Dependency Injection
OkHttp for HTTP/HTTPS Requests
Retrofit for API Mapping Datasources
Gson for Json Parser
Google Auth for Social Login with Google
Facebook Login for Social Login with Facebook

Gradle Builds

Builds are made with Kotlin DSL and generated in this directory:

<ROOT_DIR>/builds/<MODULE_NAME>

KeyStore

Algorithm	Key Size	Cipher
RSA	2048	RSA/ECB/PKCS1Padding

With the KeyStore class it is possible to encrypt and decrypt bytes in a simple way, but we have a limitation.

The maximum number of bytes supported for encryption is calculated as follows:

floor(floor(KEY_SIZE.toDouble() / 8) - 11).toInt()

If we set KEY_SIZE = 2048, we can only encrypt 248 bytes or an exception will be thrown.

To work around this problem, we can "break" an array of bytes in equal sizes of 248 bytes and encrypt part by part and concatenate the results.

For example. If we want to encrypt an array of bytes of size 485 bytes, we will break into two parts of at most 248 bytes:

248 + 237 = 485 bytes

Next, we will encrypt the first part (248 bytes) which will generates an array of bytes with a total of 256 bytes.

Finally, we will encrypt the second part (237 bytes) which will generates an array of bytes with a total of 256 bytes.

Concatenating the two parts will have an array of bytes with 512 bytes.

To decrypt this array resulting from the concatenation of these two parts, do the following:

512 / 2 = 256 bytes

The first part is decrypted, and then the second part is decrypted. Then the first part is concatenated with the second part. At the end, we will have the original byte array.

To encrypt an array of bytes use:

AppKeyStore.encode(ByteArray): ByteArray

To dencrypt an array of bytes use:

AppKeyStore.decode(ByteArray): ByteArray

Dependency Injection

Essential dependency injections happen asynchronously during Splash Screen.

Each dependency injection happens gradually as the user navigates through the App.

Network Monitor

If device is offline a message will be appear in the bottom of screen.

Web Requests

Oauth 2 for authentication.

Auto Refresh Token if necessary.

API responds with envelope:

{
  "meta": {
    "message": ""
  },
  "body": {}
}

Repositories

Writing...

Exceptions

AuthException for authentication errors.
ConnectionException for connection errors.
ServerException for server errors.
UnauthorizedException for unauthorized error.
SyncException for sync errors.

Throwable.toAppError(Context): AppError

Preferences

Values are encrypted with the AppKeyStore.

Navigation

Between Activities:

Navigator.nav(Screen, Bundle)

Between Fragments:

Navigator.nav(NavController, Int, Bundle)

Default Layouts

By default, views are included in the content container of the base layout.

Activities:

All activity base layouts are implemented by IActivityLayoutView. The default layout follows:

<androidx.constraintlayout.widget.ConstraintLayout>
    <!-- APP BAR -->
    <com.google.android.material.appbar.AppBarLayout
        android:id="@+id/appbar" 
        ... />

    <!-- CONTENT -->
    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/content"
        ... />

    <!-- LOADING -->
    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/loading"
        ... />

    <!-- MESSAGE -->
    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/message"
        ... />

    <!-- INFO -->
    <androidx.appcompat.widget.AppCompatTextView
        android:id="@+id/info"
        ... />
</androidx.constraintlayout.widget.ConstraintLayout>

Fragments:

All fragment base layouts are implemented by ILayoutView. The default layout follows:

<androidx.constraintlayout.widget.ConstraintLayout>
    <!-- CONTENT -->
    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/fragment_content"
        ... />
            
    <!-- LOADING -->
    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/fragment_loading"
        ... />

    <!-- MESSAGE -->
    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/fragment_message"
        ... />
</androidx.constraintlayout.widget.ConstraintLayout>

To create a layout for an activity:

<com.domain.skeleton.core.view.activity.ActivityView>
    <androidx.appcompat.widget.AppCompatTextView
        android:id="@+id/tv_label"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</com.domain.skeleton.core.view.activity.ActivityView>

To create a layout for a fragment:

<com.domain.skeleton.core.view.fragment.FragmentView>
    <androidx.appcompat.widget.AppCompatTextView
        android:id="@+id/tv_label"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</com.domain.skeleton.core.view.activity.ActivityView>

Default Views

All default app views are injected to all activities and fragments and are access by appViews attribute.

ToolbarView is the default toolbar view.
LoadingView is the default loading view.
UnauthorizedView is the default unauthorized view.
NoConnectionView id the default no connection message view.
CustomErrorView is the default view for custom messages.

appViews.customError.message.text = "Message"
appViews.customError.setOnClickListener {
    myFunction.invoke()
}

rootView.setMessage(appViews.customError)

1. Configure your project

1.1. Google SDK

1.1.1. Create Project

https://console.developers.google.com > New Project

1.1.2. Enable API

Dashboard > Enable APIs and Services > Search for "Google People" > Enable

1.1.3. Create Credentials

Overview > Create Credentials

Get Fingerprint (SHA-1):

keytool -importkeystore \
        -srckeystore ~/.android/debug.keystore \
        -destkeystore ~/.android/debug.keystore \
        -deststoretype pkcs12

keytool -keystore ~/.android/debug.keystore -list -v

Set Package Name:

com.domain.skeleton

1.2. Facebook SDK

1.2.1. Create Project

https://developers.facebook.com/apps > Add New Project

1.2.2. Enable API

Login do Facebook > Inicio Rapido > Android

Package Name:

com.domain.skeleton

Class:

com.domain.skeleton.auth.activity.LoginActivity

1.2.3. Generate Hash Key

Debug:

keytool -exportcert -alias androiddebugkey -keystore ~/.android/debug.keystore | openssl sha1 -binary | openssl base64

Release:

keytool -exportcert -alias YOUR_RELEASE_KEY_ALIAS -keystore YOUR_RELEASE_KEY_PATH | openssl sha1 -binary | openssl base64

Paste Hash Key:

/core/res/values/system.xml

<string name="api_facebook_app_id">APP_ID</string>
<string name="api_facebook_login_protocol_scheme">LOGIN_PROTOCOL_SCHEME</string>

2. Configure Local Server

2.1. Clone Project

git clone https://github.com/junioregis/skeleton-rails.git

2.2. Follow the steps from the Wiki

https://github.com/junioregis/skeleton-rails/wiki

Start the local server.

junioregis/skeleton-android