Android Jetpack Preferences DataStore Example

Arun Chandravanshi

6 years ago

This blog is about Android Jetpack DataStore Preferences and how to implement DataStore Preferences in our Android application.

DOWNLOAD CODE

DataStore

Jetpack DataStore is a data storage solution.
It allows us to store key-value pairs (like SharedPreferences) or typed objects with protocol buffers (discuss in the next article).
DataStore uses Kotlin, Coroutines and Flow to store data asynchronously with consistency and transaction support.
DataStore is the new data storage solution which is the replacement of SharedPreferences.

Types of DataStore

DataStore provides two different types of implementations to store data.

Preferences DataStore — This uses key-value pairs to store data. But it doesn’t provide type-safety.
Proto DataStore — It stores data as a custom type with specified schema using Protocol Buffers (discuss in the next article).

Creating new project

Create a new project by going to File ⇒ New Android Project, select Empty Activity , provide app name, select language to kotlin and then finally click on finish.
Open project’s app level build.gradle file:

Go to the android block and add the below lines.

compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
}

kotlinOptions {
    jvmTarget = '1.8'
}

Now add the below dependencies inside dependencies block. Once you have added all these, sync your project.

dependencies { 
    // Preferences DataStore
    implementation "androidx.datastore:datastore-preferences:1.0.0-alpha07"

    // Lifecycle component
    implementation "androidx.lifecycle:lifecycle-livedata-ktx:2.2.0"

    // Kotlin coroutines components
    api "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.9"
    api "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.9"

}

3 . Open your activity_main.xml. To create the following UI, add the below code.

activity_main.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="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/btn_save"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/margin_60dp"
        android:background="@drawable/background"
        android:padding="@dimen/padding_18dp"
        android:text="Save user"
        android:textColor="@android:color/white"
        android:textSize="@dimen/textsize_15sp"
        android:textStyle="bold"
        app:layout_constraintEnd_toEndOf="@+id/switch_gender"
        app:layout_constraintStart_toStartOf="@+id/switch_gender"
        app:layout_constraintTop_toBottomOf="@+id/switch_gender" />

    <EditText
        android:id="@+id/et_lname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/margin_16dp"
        android:ems="10"
        android:hint="@string/hint_enter_last_name"
        app:layout_constraintEnd_toEndOf="@+id/et_fname"
        app:layout_constraintStart_toStartOf="@+id/et_fname"
        app:layout_constraintTop_toBottomOf="@+id/et_fname" />

    <EditText
        android:id="@+id/et_age"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/margin_16dp"
        android:ems="10"
        android:hint="@string/hint_enter_age"
        android:inputType="number"
        app:layout_constraintEnd_toEndOf="@+id/et_lname"
        app:layout_constraintStart_toStartOf="@+id/et_lname"
        app:layout_constraintTop_toBottomOf="@+id/et_lname"
        tools:layout_editor_absoluteY="317dp" />

    <EditText
        android:id="@+id/et_fname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/margin_30dp"
        android:ems="10"
        android:hint="@string/hint_enter_first_name"
        app:layout_constraintEnd_toEndOf="@+id/tv_gender"
        app:layout_constraintStart_toStartOf="@+id/tv_gender"
        app:layout_constraintTop_toBottomOf="@+id/tv_gender"
        tools:layout_editor_absoluteY="178dp" />

    <TextView
        android:id="@+id/tv_fname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/margin_30dp"
        android:textStyle="bold"
        android:textColor="@color/colorPrimaryDark"
        android:textSize="@dimen/textsize_20sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/tv_lname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/margin_16dp"
        android:textStyle="bold"
        android:textColor="@color/colorPrimaryDark"
        android:textSize="@dimen/textsize_20sp"
        app:layout_constraintEnd_toEndOf="@+id/tv_fname"
        app:layout_constraintStart_toStartOf="@+id/tv_fname"
        app:layout_constraintTop_toBottomOf="@+id/tv_fname" />

    <TextView
        android:id="@+id/tv_age"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/margin_16dp"
        android:textStyle="bold"
        android:textColor="@color/colorPrimaryDark"
        android:textSize="@dimen/textsize_20sp"
        app:layout_constraintEnd_toEndOf="@+id/tv_lname"
        app:layout_constraintStart_toStartOf="@+id/tv_lname"
        app:layout_constraintTop_toBottomOf="@+id/tv_lname" />

    <TextView
        android:id="@+id/tv_gender"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/margin_16dp"
        android:textStyle="bold"
        android:textColor="@color/colorPrimaryDark"
        android:textSize="@dimen/textsize_20sp"
        app:layout_constraintEnd_toEndOf="@+id/tv_age"
        app:layout_constraintStart_toStartOf="@+id/tv_age"
        app:layout_constraintTop_toBottomOf="@+id/tv_age" />

    <androidx.appcompat.widget.SwitchCompat
        android:id="@+id/switch_gender"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/margin_16dp"
        android:text="@string/female_male"
        android:textSize="@dimen/textsize_20sp"
        app:layout_constraintEnd_toEndOf="@+id/et_age"
        app:layout_constraintStart_toStartOf="@+id/et_age"
        app:layout_constraintTop_toBottomOf="@+id/et_age" />

</androidx.constraintlayout.widget.ConstraintLayout>

Creating a Preferences DataStore

4. Create a new kotlin file User.kt and add the below code.

User.kt

package com.c1ctech.jetpackdatastore

import android.content.Context
import androidx.datastore.core.DataStore
import androidx.datastore.preferences.core.Preferences
import androidx.datastore.preferences.preferencesDataStore

// At the top level of your kotlin file
val Context.dataStore: DataStore<Preferences> by preferencesDataStore(name = "user_prefs")

dataStore: instance of Datastore<Preferences> created by preferencesDataStore.
name parameter(mandatory) : is the name of the Preferences DataStore.

5 .Create a new kotlin class UserManager.kt and add the below code.

UserManager.kt

package com.c1ctech.jetpackdatastore

import androidx.datastore.core.DataStore
import androidx.datastore.preferences.core.*
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.map

class UserManager(val dataStore: DataStore<Preferences>) {

    //Create some keys
    companion object {
        val USER_AGE_KEY = intPreferencesKey("USER_AGE")
        val USER_FIRST_NAME_KEY = stringPreferencesKey("USER_FIRST_NAME")
        val USER_LAST_NAME_KEY = stringPreferencesKey("USER_LAST_NAME")
        val USER_GENDER_KEY = booleanPreferencesKey("USER_GENDER")
    }

    //Store user data
    suspend fun storeUser(age: Int, fname: String, lname: String, isMale: Boolean) {
        dataStore.edit {
            it[USER_AGE_KEY] = age
            it[USER_FIRST_NAME_KEY] = fname
            it[USER_LAST_NAME_KEY] = lname
            it[USER_GENDER_KEY] = isMale

        }
    }

    //Create an age flow
    val userAgeFlow: Flow<Int?> = dataStore.data.map {
        it[USER_AGE_KEY]
    }

    //Create a fname flow
    val userFirstNameFlow: Flow<String?> = dataStore.data.map {
        it[USER_FIRST_NAME_KEY]
    }

    //Create a lname flow
    val userLastNameFlow: Flow<String?> = dataStore.data.map {
        it[USER_LAST_NAME_KEY]
    }

    //Create a gender flow
    val userGenderFlow: Flow<Boolean?> = dataStore.data.map {
        it[USER_GENDER_KEY]
    }

}

Defining Key for the Value that needs to be saved:

To define a key for each value that you need to store in the DataStore<Preferences> instance, you must use the corresponding key type function. For example:

val USER_AGE_KEY = intPreferencesKey("USER_AGE")
val USER_FIRST_NAME_KEY = stringPreferencesKey("USER_FIRST_NAME")
val USER_LAST_NAME_KEY = stringPreferencesKey("USER_LAST_NAME")
val USER_GENDER_KEY = booleanPreferencesKey("USER_GENDER")

Saving Value to Preference DataStore:

Preferences DataStore provides an edit () function using which we can save our values to keys.

Reading Value back from Preference DataStore:

To read the value from a Preferences DataStore we need to use the DataStore.data property which returns a Flow<Preferences> and with the .map{} operator we can can get the Flow<> (value) by passing the right key into the preferences.

6 . Open MainActivity.kt and add the below code.

MainActivity.kt

package com.c1ctech.jetpackdatastore

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.lifecycle.asLiveData
import androidx.lifecycle.observe
import kotlinx.android.synthetic.main.activity_main.*
import kotlinx.coroutines.GlobalScope
import kotlinx.coroutines.launch

class MainActivity : AppCompatActivity() {
    lateinit var userManager: UserManager
    var age = 0
    var fname = ""
    var lname = ""
    var gender = ""

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        //Get reference to our userManager class
        userManager = UserManager(dataStore)

        buttonSave()

        observeData()
    }

    private fun observeData() {

        //Updates age
        userManager.userAgeFlow.asLiveData().observe(this, {
            if (it != null) {
                age = it
                tv_age.text = it.toString()
            }
        })

        //Updates firstname
        userManager.userFirstNameFlow.asLiveData().observe(this, {
            if (it != null) {
                fname = it
                tv_fname.text = it
            }
        })

        //Updates lastname
        userManager.userLastNameFlow.asLiveData().observe(this, {
            if (it != null) {
                lname = it
                tv_lname.text = it
            }
        })

        //Updates gender
        userManager.userGenderFlow.asLiveData().observe(this, {
            if (it != null) {
                gender = if (it) "Male" else "Female"
                tv_gender.text = gender
            }
        })
    }

    private fun buttonSave() {

        //Gets the user input and saves it
        btn_save.setOnClickListener {
            fname = et_fname.text.toString()
            lname = et_lname.text.toString()
            age = et_age.text.toString().toInt()
            val isMale = switch_gender.isChecked

            //Stores the values
            GlobalScope.launch {
                userManager.storeUser(age, fname, lname, isMale)
            }
        }
    }
}

In order to get the saved values in the activity from the DataStore, we need to change the Flow<> to LiveData with .asLiveData() and observe it.

DataStore

Types of DataStore

Creating new project

Creating a Preferences DataStore

Share this: