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In this post, we gonna talk about firebase in-app messaging in android.

Overview

Firebase In-App Messaging helps you engage your app’s active users by sending them targeted, contextual message. Encourage them to use key app features. For example, you can send an in-pp message to get users to subscribe, watch a video, complete a level, or buy an items. I’m sure you guys familiar. If you had android app you often get in-app message.

You can customized message as card, banners, models, or images. You can also set up a trigger so that they appear exactly when they’d benefit. It is very similar to cloud messaging, except for messages sent to the app, not a device. So if you talk about cloud messaging.

Uses of In-App Messaging

You should use Firebase In-App Messaging to encourage exploration and discovery. Highlight a sale or coupon in your eCommerce app. Give clues or tips in your game. Prompt a like or share in your social media app. These types of things, So kind of different use case or messaging.

Key Capabilities of In App Messaging

  • Send relevant, engaging messages
  • Sends messages when they are most needed, while users are actually in your app.
  • Promote a big sale when users visit your In-app store. etc.
  • Target messages by audience or behavior.
    • Work with Analytics and Predictions to give you tools to deliver the message to the user you would most like to reach
    • Send messages based on user’s demographics, past behaviors, or even predictions of their future behaviors.
  • Create flexible, custom alerts –
    • You can create a flexible, custom alert and have the ability to customize your style appearance display triggers and content.
    • These will help you do everything from sending promotional offers to getting users to update a new version of the app.

Implementations Step

Now I want to show you, how you can setup and configure to use In App Messaging for Firebase.

  • Connect your app – Start by adding Firebase to your app in the firebase console
  • Integrates the SDK – Add the firebase In-App Messaging SDK to your app via Gradle.
  • Create your first message – Visit the Firebase console to write, customize, and target your first message.

Connect your app

Let’s open android studio, and create a simple project. For now It doesn’t have anything extra on it. It just MainActivity that’s empty.

The first thing we’re gonna to do we’re going to add this project to Firebase. Fo doing that we need to know is the package name, In this example, I’m using com.firebaseinappmessaging .

Now let’s go to the firebase console and go to the project. Then just add the app and go through the steps the adding an app by entering package name. Still, you are facing any issue, follow this article.

Now you have to download json file, So go to settings and download on google-service.json file in app folder.

Integrates the SDK

Now back to the Android Studio, Now we have to update Gradle file. So go to the project build.gradle file and add these dependencies. Something like below

    // Import the Firebase BoM
    implementation 'com.google.firebase:firebase-inappmessaging-display-ktx:19.1.5'
    implementation 'com.google.firebase:firebase-analytics-ktx:18.0.2'

Let’s sync the project, That all about configuration. For sending a test message you have to need AppInstaceId, Basically firebase console allow us send messaging to specific device.

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.appcompat.widget.AppCompatTextView
        android:id="@+id/textView2"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="8dp"
        android:layout_marginBottom="16dp"
        android:text="@string/warning_fresh_install"
        android:textSize="18sp"
        app:layout_constraintBottom_toTopOf="@+id/instanceIdText"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <androidx.appcompat.widget.AppCompatTextView
        android:id="@+id/instanceIdText"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        android:text="@string/warning_fresh_install"
        android:textSize="18sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView2"
        tools:text="Device Instance ID: 1234" />

    <androidx.appcompat.widget.AppCompatButton
        android:id="@+id/eventTriggerButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginBottom="8dp"
        android:background="@color/purple_200"
        android:text="@string/button_text"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView2" />

</androidx.constraintlayout.widget.ConstraintLayout>
package com.example.firebaseinappmessaging

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import com.google.android.gms.tasks.OnSuccessListener
import com.google.firebase.inappmessaging.FirebaseInAppMessaging
import com.google.firebase.inappmessaging.display.ktx.FirebaseInAppMessagingDisplayKtxRegistrar
import com.google.firebase.installations.FirebaseInstallations
import com.google.firebase.ktx.Firebase
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    private lateinit var firebaseIam: FirebaseInAppMessaging
    //private lateinit var firebaseAnalytics: FirebaseAnalytics
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // firebaseAnalytics = FirebaseAnalytics.getInstance(this)
        firebaseIam = FirebaseInAppMessaging.getInstance()

        firebaseIam.isAutomaticDataCollectionEnabled = true
        firebaseIam.setMessagesSuppressed(false)

        eventTriggerButton.setOnClickListener { view ->
            //firebaseAnalytics.logEvent("engagement_party", Bundle())
            firebaseIam.triggerEvent("engagement_party")
        }

        // Get and display/log the Instance ID
        FirebaseInstallations.getInstance().id.addOnSuccessListener {
            instanceIdText.text = getString(R.string.instance_id_fmt, it)
            Log.d(TAG, "InstanceId: $it")
        }
//            .addOnSuccessListener(object : OnSuccessListener<InstanceIdResult> {
//                override fun onSuccess(instanceIdResult: InstanceIdResult) {
//                    val instanceId = instanceIdResult.id
//                    instanceIdText.text = getString(R.string.instance_id_fmt, instanceId)
//                    Log.d(TAG, "InstanceId: $instanceId")
//                }
//            })

        addClickListener()
    }
    private fun addClickListener() {
        val listener = InAppMessageClickListener()
        firebaseIam.addClickListener(listener)
    }

    private fun suppressMessages() {
        firebaseIam.setMessagesSuppressed(true)
    }

    private fun enableDataCollection() {
        // Only needed if firebase_inapp_messaging_auto_data_collection_enabled is set to
        // false in AndroidManifest.xml
        firebaseIam.isAutomaticDataCollectionEnabled = true
    }

    companion object {

        private const val TAG = "FirebaseInAppMessaging"
    }
}
package com.example.firebaseinappmessaging

import android.util.Log
import com.google.firebase.inappmessaging.FirebaseInAppMessagingClickListener
import com.google.firebase.inappmessaging.model.Action
import com.google.firebase.inappmessaging.model.InAppMessage


class InAppMessageClickListener : FirebaseInAppMessagingClickListener {

    override fun messageClicked(inAppMessage: InAppMessage, action: Action) {
        // Determine which URL the user clicked
        val url = action.actionUrl

        // Get general information about the campaign
        val metadata = inAppMessage.campaignMetadata

        Log.d("AppTest", "URL is: " + url)
        Log.d("AppTest", "Meta Data: " + metadata)
    }
}

In this blog, we will learn how to use retrofit with coroutines Kotlin in android application, with the help of an example. So we are actually building an application in android using Coroutines, Retrofit and MVVM, and so on. So lets started.

Objectives

Basically, the purpose of the project is to get the list of users information from the endpoints and display it to users in RecyclerView. I’m listing them below of these are objectives of this Retrofit coroutines example blog.

  • Get a list of user’s info from an endpoint using REST API. Basically
  • Use coroutines with Retrofit and MVVM
  • Display the user’s info in a RecyclerView

So the main idea is to show you, how you can build a professional application using a proper architecture with Retrofit and using coroutines to get some information from a webserver. so that is what we are building.

Requirements

Now, there are some requirements for this retrofit coroutines example app. These are listed below

  • Android knowledge
  • Retrofit
  • MVVM

So idea is, I’m not going to details of these, you have to basic idea of these items. You should know how retrofit works with MVVM. I’m going to focus, this example on coroutines that work with Retrofit and MVVM.

All right guys, so lets started quickly with this example app. Open AndroidStudio and create a new android project with some template.

Setting up the project

Let wait for sync of project, that recently you created. And first of all let’s add internet permission in AndroidManifest that is obvious, Because we are communicating with backend APIs. So we do need that

    <uses-permission android:name="android.permission.INTERNET"/>

All right then next step is we have to add below dependency in app build.gradle.

  • RecyclerView
  • Glide
  • Retrofit
  • Lifecycle extensions
  • Coroutines
    // RecyclerView dependency
    implementation "androidx.recyclerview:recyclerview:1.1.0"
    implementation "androidx.swiperefreshlayout:swiperefreshlayout:1.1.0"
    // Glide dependency
    implementation 'com.github.bumptech.glide:glide:4.11.0'
    // Retrofit dependency
    implementation 'com.squareup.retrofit2:retrofit:2.7.1'
    implementation 'com.squareup.retrofit2:converter-gson:2.6.0'
    // Lifecycle dependency
    implementation 'android.arch.lifecycle:extensions:1.1.1'
    // Coroutines dependency
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.9'
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.9'

Backend API Endpoint and JSON

So first of all, we require a REST API, that we have to consume in this project. You can use whatever you required. For now, I’m consuming this URL and json response is

{
  "page": 1,
  "per_page": 6,
  "total": 12,
  "total_pages": 2,
  "data": [
    {
      "id": 1,
      "email": "george.bluth@reqres.in",
      "first_name": "George",
      "last_name": "Bluth",
      "avatar": "https://reqres.in/img/faces/1-image.jpg"
    },
    {
      "id": 2,
      "email": "janet.weaver@reqres.in",
      "first_name": "Janet",
      "last_name": "Weaver",
      "avatar": "https://reqres.in/img/faces/2-image.jpg"
    },
    {
      "id": 3,
      "email": "emma.wong@reqres.in",
      "first_name": "Emma",
      "last_name": "Wong",
      "avatar": "https://reqres.in/img/faces/3-image.jpg"
    }
    .
    .
    .
  ]
}

Create user Model

Now, we are following the MVVM design pattern in this coroutines example. So I’m creating a data class for parsing above JSON resonse. Let create a data class named is UserList.kt

package com.retrofitcoroutines.example.model

import com.google.gson.annotations.SerializedName

data class UserList(
    @SerializedName("page") val page: Int,
    @SerializedName("per_page") val per_page: Int,
    @SerializedName("total") val total: Int,
    @SerializedName("total_pages") val total_pages: Int,
    @SerializedName("data") val data: List<User>
)
 

Let’s create another data class named User.kt

package com.retrofitcoroutines.example.model

import com.google.gson.annotations.SerializedName

data class User(
    @SerializedName("id") val id : Int,
    @SerializedName("email") val email : String,
    @SerializedName("first_name") val first_name : String,
    @SerializedName("last_name") val last_name : String,
    @SerializedName("avatar") val avatar : String
)

Update the activity_main.xml

Now in main_activity has below layout, So we have a RecyclerView, then TextView in case of error, we can display a message. And we have a ProgressBar, so user know that is something is going in background. So its quite simple you know. So there are 3 element and we’re going to hide to show these element.

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".view.MainActivity">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/usersList"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginStart="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginBottom="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/listError"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginStart="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginBottom="8dp"
        android:gravity="center"
        tools:text="Error"
        android:textColor="#FA1302"
        android:textSize="18sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ProgressBar
        android:id="@+id/loadingView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginBottom="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout> 

Create a ViewModel

Let create a ViewModel named is ListViewModel. Here we simply fetching user list from backend server and passes that data to our MutableLiveData. Apart from this, we have a load error which generates an error message in case of API failure. and we have a loading MutableLiveData(), That let us know there is something happens in background.

package com.retrofitcoroutines.example.viewmodel

import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.ViewModel
import com.retrofitcoroutines.example.model.User
import com.retrofitcoroutines.example.remote.UserService
import kotlinx.coroutines.*

class ListViewModel : ViewModel() {

    val userService = UserService().getUsersService()
    var job: Job? = null
    val exceptionHandler = CoroutineExceptionHandler { coroutineContext, throwable ->
        onError("Exception handled: ${throwable.localizedMessage}")
    }

    val users = MutableLiveData<List<User>>()
    val usersLoadError = MutableLiveData<String?>()
    val loading = MutableLiveData<Boolean>()

    fun refresh() {
        fetchUsers()
    }

    private fun fetchUsers() {
        loading.value = true
        job = CoroutineScope(Dispatchers.IO + exceptionHandler).launch {
            val response = userService.getUsers()
            withContext(Dispatchers.Main) {
                if (response.isSuccessful) {
                    users.value = response.body()?.data
                    usersLoadError.value = null
                    loading.value = false
                } else {
                    onError("Error : ${response.message()} ")
                }
            }
        }
        usersLoadError.value = ""
        loading.value = false
    }

    private fun onError(message: String) {
        usersLoadError.value = message
        loading.value = false
    }

    override fun onCleared() {
        super.onCleared()
        job?.cancel()
    }

} 

Connect ListViewModel to MainActivity

In the MainActivity we are instantiating the ListViewModel. Then we simply set up our RecycleView, Using a UserAdapter, That we’ll create below of the code, and then we are observing the ViewModel, which simply connecting Livedata from the ViewModel and proceeding to update the interface based on the information that we received. So all is that we need to do.

package com.retrofitcoroutines.example.view

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import androidx.lifecycle.Observer
import androidx.lifecycle.ViewModelProviders
import androidx.recyclerview.widget.LinearLayoutManager
import com.retrofitcoroutines.example.R
import com.retrofitcoroutines.example.viewmodel.ListViewModel
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {
    lateinit var viewModel: ListViewModel
    private val userListAdapter = UserListAdapter(arrayListOf())

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        viewModel = ViewModelProviders.of(this).get(ListViewModel::class.java)
        viewModel.refresh()

        usersList.apply {
            layoutManager = LinearLayoutManager(context)
            adapter = userListAdapter
        }

        observeViewModel()
    }
    private fun observeViewModel() {
        viewModel.users.observe(this, Observer {countries ->
            countries?.let {
                usersList.visibility = View.VISIBLE
                userListAdapter.updateCountries(it) }
        })

        viewModel.usersLoadError.observe(this, Observer { isError ->
            listError.visibility = if(isError == "") View.GONE else View.VISIBLE
        })

        viewModel.loading.observe(this, Observer { isLoading ->
            isLoading?.let {
                loadingView.visibility = if(it) View.VISIBLE else View.GONE
                if(it) {
                    listError.visibility = View.GONE
                    usersList.visibility = View.GONE
                }
            }
        })
    }
}

Now create UserListAdapter

Simply create a RecyclerView Adapter and attached the user_item view to recycler as usual. The only different thing here is the extension function for ImageView to load the image which allows us to loan an image on ImageView based on the URL we have.

package com.retrofitcoroutines.example.view

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import com.retrofitcoroutines.example.R
import com.retrofitcoroutines.example.model.User
import com.retrofitcoroutines.example.utils.loadImage
import kotlinx.android.synthetic.main.item_user.view.*

class UserListAdapter(var users: ArrayList<User>): RecyclerView.Adapter<UserListAdapter.UserViewHolder>() {

    fun updateCountries(newUsers: List<User>) {
        users.clear()
        users.addAll(newUsers)
        notifyDataSetChanged()
    }

    override fun onCreateViewHolder(parent: ViewGroup, p1: Int) = UserViewHolder(
        LayoutInflater.from(parent.context).inflate(R.layout.item_user, parent, false)
    )

    override fun getItemCount() = users.size

    override fun onBindViewHolder(holder: UserViewHolder, position: Int) {
        holder.bind(users[position])
    }

    class UserViewHolder(view: View): RecyclerView.ViewHolder(view) {

        private val imageView = view.userAvatar
        private val userName = view.userFullName
        private val userEmail = view.userEmail


        fun bind(user: User) {
            userName.text = user.first_name + " "+ user.last_name
            userEmail.text = user.email
            imageView.loadImage(user.avatar)
        }
    }
}

Here is item_user.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="8dp"
    android:background="#E4DDF3">

    <ImageView
        android:id="@+id/userAvatar"
        android:layout_width="80dp"
        android:layout_height="80dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@mipmap/ic_launcher_round" />

    <TextView
        android:id="@+id/userFullName"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="16dp"
        android:textColor="@color/colorPrimaryDark"
        android:textSize="18sp"
        android:textStyle="bold"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/userAvatar"
        app:layout_constraintTop_toTopOf="parent"
        tools:text="Morris" />

    <TextView
        android:id="@+id/userEmail"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="16dp"
        tools:text="morris@androidwave.com"
        android:textSize="16sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/userAvatar"
        app:layout_constraintTop_toBottomOf="@+id/userFullName" />
</androidx.constraintlayout.widget.ConstraintLayout>

Write a extension function for ImageView

Here I have created a new package named is utils and writes below extension function.

package com.retrofitcoroutines.example.utils

import android.widget.ImageView
import com.bumptech.glide.Glide
import com.bumptech.glide.request.RequestOptions
import com.retrofitcoroutines.example.R

fun ImageView.loadImage(uri: String?) {
    val options = RequestOptions()
        .error(R.mipmap.ic_launcher_round)
    Glide.with(this.context)
        .setDefaultRequestOptions(options)
        .load(uri)
        .into(this)
}
  

That all about UI let setup Retrofit and connect it with project.

Setting up Retrofit

Let create a retrofit interface. Here I’m gonna set up a GET function for Retrofit. Inside this interface create a suspending function like below. It simply returns us a Response.

package com.retrofitcoroutines.example.remote

import com.retrofitcoroutines.example.model.UserList
import retrofit2.Response
import retrofit2.http.GET

interface UserApi {

    @GET("users")
    suspend fun getUsers(): Response<UserList>

} 

Create a UsersService

In this class, first of I have created a variable here is BASE_URL. After that I have created a function named is getUsersService() that simply returns UserApi that we just defined earlier.

package com.retrofitcoroutines.example.remote

import retrofit2.Retrofit
import retrofit2.converter.gson.GsonConverterFactory

class UserService {
    
    private val BASE_URL = "https://reqres.in/api/";
    fun getUsersService(): UserApi{
       return Retrofit.Builder()
           .baseUrl(BASE_URL)
           .addConverterFactory(GsonConverterFactory.create())
           .build()
           .create(UserApi::class.java)
    }
}

That all done, let’s go ahead and run the code and see if it works. It’s working so we have all users that return from APIs in the context of coroutines. Basically, in this example, we have two coroutines because first, we are calling with Dispatchers.IO and finally we are calling Dispatchers.Main. So way we can update UI in main. thread. That code I already added in ViewModel, for reference I adding again

CoroutineScope(Dispatchers.IO + exceptionHandler).launch {
            val response = userService.getUsers()
            withContext(Dispatchers.Main) {
                if (response.isSuccessful) {
                    users.value = response.body()?.data
                    usersLoadError.value = null
                    loading.value = false
                } else {
                    onError("Error : ${response.message()} ")
                }
            }
        } 

Conclusion

So that is it, So we learned how to use Retrofit with coroutines in Kotlin| Android.  I hope it’s helpful for you, Help me by sharing this post with all your friends who learning android app development.

Download Source Code

Retrofit coroutines error handling

will publish a complete article on that, For now you can follow this article

Retrofit with coroutines

This is a sample app thats created. Please follow this article only

Hello folks! In this article, We’ll learn the best practices of SharedPreferences in Android(Kotlin). I’ll show you, how we can store and retrieve values in SharedPreferences. For better understanding, I’ll create an android SharedPreferences example (Sample app) and take an example of Writing and Reading Values in SharedPreferences. So let started

What are SharePreferences?

SharedPreferences is an android API that stores app data using key-value pairs and provides simple methods to read and write them.

Android system provides several options for you to save your data. These options are App-specific storage, Shared storage, Preferences, Databases. SharePreferences comes in Preference. It offers a framework to save private, primitive data in key-value pairs.

Why SharePreferences?

They’re mostly used to store user states when it comes to user settings or keeps a piece of small information(User details etc.) without needing storage permission. As per my opinion, you should store small primitive value in Preferences such as booleans, ints, longs, floats, and strings.

Modes in SharePreferences

SharedPreferences have different MODE these are below

1. Create a android application

Let take an example, open android studio, and create a new project. Now create a interface named is IPreferenceHelper. In this Interface we are defining some getter setter for storing or retrieving preference value. such as ApiKey and UserId etc.

package com.sharedpreferencesexample

interface IPreferenceHelper {

    fun setApiKey(apiKey: String)

    fun getApiKey(): String

    fun setUserId(userId: String)

    fun getUserId(): String

    fun clearPrefs()

}

2. Create a singleton class for managing Preferences

Ideally SharedPreferences store the app level value, So the SharedPreferences instance should be single threw out the app. It should be a singleton. Let create a Singletone class named is PreferenceManager and implement IPreferenceHelper. Just like below

open class PreferenceManager constructor(context: Context) : IPreferenceHelper {
    private val PREFS_NAME = "SharedPreferenceDemo"
    private var preferences: SharedPreferences

    init {
        preferences = context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE)
    }

    override fun setApiKey(apiKey: String) {
        preferences[API_KEY] = apiKey
    }

    override fun getApiKey(): String {
        return preferences[API_KEY] ?: ""
    }

    override fun setUserId(userId: String) {
        preferences[USER_ID] = userId
    }

    override fun getUserId(): String {
        return preferences[USER_ID] ?: ""
    }

    override fun clearPrefs() {
        preferences.edit().clear().apply()
    }

    companion object {
        const val API_KEY = "api_key"
        const val USER_ID = "user_id"
    }
}

3. Write into your SharedPreferences

Normally, writing into SharedPreferences is simple. But I’m going to write a Kotlin extension, This extension is make writing very simple and reduce boilerplate code.

/**
 * SharedPreferences extension function, to listen the edit() and apply() fun calls
 * on every SharedPreferences operation.
 */
private inline fun SharedPreferences.edit(operation: (SharedPreferences.Editor) -> Unit) {
    val editor = this.edit()
    operation(editor)
    editor.apply()
}

/**
 * puts a key value pair in shared prefs if doesn't exists, otherwise updates value on given [key]
 */
private operator fun SharedPreferences.set(key: String, value: Any?) {
    when (value) {
        is String? -> edit { it.putString(key, value) }
        is Int -> edit { it.putInt(key, value) }
        is Boolean -> edit { it.putBoolean(key, value) }
        is Float -> edit { it.putFloat(key, value) }
        is Long -> edit { it.putLong(key, value) }
        else -> throw UnsupportedOperationException("Not yet implemented")
    }
}

4.  Read from SharedPreferences

Reading a value from SharedPreferences is also straightforward. I’m going to write another useful extension that provides more control over retrieving a value from SharedPreferences. Let check below code

/**
 * finds value on given key.
 * [T] is the type of value
 * @param defaultValue optional default value - will take null for strings, false for bool and -1 for numeric values if [defaultValue] is not specified
 */
private inline operator fun <reified T : Any> SharedPreferences.get(
    key: String,
    defaultValue: T? = null
): T? {
    return when (T::class) {
        String::class -> getString(key, defaultValue as? String) as T?
        Int::class -> getInt(key, defaultValue as? Int ?: -1) as T?
        Boolean::class -> getBoolean(key, defaultValue as? Boolean ?: false) as T?
        Float::class -> getFloat(key, defaultValue as? Float ?: -1f) as T?
        Long::class -> getLong(key, defaultValue as? Long ?: -1) as T?
        else -> throw UnsupportedOperationException("Not yet implemented")
    }
}

5. Finally your PreferenceManager class look like below

package com.sharedpreferencesexample

import android.content.Context
import android.content.SharedPreferences

open class PreferenceManager constructor(context: Context) : IPreferenceHelper {
    private val PREFS_NAME = "SharedPreferenceDemo"
    private var preferences: SharedPreferences

    init {
        preferences = context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE)
    }

    override fun setApiKey(apiKey: String) {
        preferences[API_KEY] = apiKey
    }

    override fun getApiKey(): String {
        return preferences[API_KEY] ?: ""
    }

    override fun setUserId(userId: String) {
        preferences[USER_ID] = userId
    }

    override fun getUserId(): String {
        return preferences[USER_ID] ?: ""
    }

    override fun clearPrefs() {
        preferences.edit().clear().apply()
    }

    companion object {
        const val API_KEY = "api_key"
        const val USER_ID = "user_id"
    }
}


/**
 * SharedPreferences extension function, to listen the edit() and apply() fun calls
 * on every SharedPreferences operation.
 */
private inline fun SharedPreferences.edit(operation: (SharedPreferences.Editor) -> Unit) {
    val editor = this.edit()
    operation(editor)
    editor.apply()
}

/**
 * puts a key value pair in shared prefs if doesn't exists, otherwise updates value on given [key]
 */
private operator fun SharedPreferences.set(key: String, value: Any?) {
    when (value) {
        is String? -> edit { it.putString(key, value) }
        is Int -> edit { it.putInt(key, value) }
        is Boolean -> edit { it.putBoolean(key, value) }
        is Float -> edit { it.putFloat(key, value) }
        is Long -> edit { it.putLong(key, value) }
        else -> throw UnsupportedOperationException("Not yet implemented")
    }
}

/**
 * finds value on given key.
 * [T] is the type of value
 * @param defaultValue optional default value - will take null for strings, false for bool and -1 for numeric values if [defaultValue] is not specified
 */
private inline operator fun <reified T : Any> SharedPreferences.get(
    key: String,
    defaultValue: T? = null
): T? {
    return when (T::class) {
        String::class -> getString(key, defaultValue as? String) as T?
        Int::class -> getInt(key, defaultValue as? Int ?: -1) as T?
        Boolean::class -> getBoolean(key, defaultValue as? Boolean ?: false) as T?
        Float::class -> getFloat(key, defaultValue as? Float ?: -1f) as T?
        Long::class -> getLong(key, defaultValue as? Long ?: -1) as T?
        else -> throw UnsupportedOperationException("Not yet implemented")
    }
}

6. Access PreferenceManager into your presentation layers

Yes, Now your PreferenceManager class is ready for use. You can initialize PreferenceManager class into your ViewModel and Activity/Fragment, Make sure the context should be applicationContext.

7. Now open the activity_main.xml and paste below code.

For making interesting example I have added two edit text and one button in this layout

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16dp"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:text="Hello World!" />

    <EditText
        android:id="@+id/editText"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="textPersonName"
        android:text="User Id"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/editText2"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:ems="10"
        android:inputType="textPersonName"
        android:text="API Key"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/editText" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="32dp"
        android:text="Show Preference Data"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/editText2" />

</androidx.constraintlayout.widget.ConstraintLayout>

8. Let access PreferenceManager class in your source file

Let’s check the below code This way you can easily read and write the value in SharePreferences

package com.sharedpreferencesexample

import android.annotation.SuppressLint
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    private val preferenceHelper: IPreferenceHelper by lazy { PreferenceManager(applicationContext) }

    @SuppressLint("SetTextI18n")
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        // display saved data
        textView.text =
            " API Key - > ${preferenceHelper.getApiKey()} \n User Id -> ${preferenceHelper.getUserId()}"
        button.setOnClickListener {
            // Update data in SharedPreference
            preferenceHelper.setApiKey(editText.text.toString())
            preferenceHelper.setUserId(editText2.text.toString())
            // display saved data
            textView.text =
                " API Key - > ${preferenceHelper.getApiKey()} \n User Id -> ${preferenceHelper.getUserId()}"
        }

    }
}

7. Build & Test

Let run the app, in a movement your app will up and run, Now enter few value these EditText and click button. The value will display on TextView. This way you can read and write small amount of data in key-value pairs!

Conclusion

In this android SharedPreferences example, we’ll learn how we can save and retrieve value in SharedPreferences. I try to follow best practices for android development. Still, you want to improve… Most Welcome

Follow this article to detect network change in Android!