kotlin android sharedpreferences

Android Shared Preferences allow the activities or applications to store and retrieve data in the form of key and value. The data stored in the application remains to persist even if the app is closed until it has deleted or cleared.

The Android setting files use Shared Preferences to store the app setting data in the form of XML file under data/data/{application package}/share_prefs directory.

To access the Shared Preferences in our application, we need to get the instance of it using any of the following methods.

getPreferences()
getSharedPreferences()
getDefaultSharedPreferences()

val sharedPreferences: SharedPreferences = this.getSharedPreferences(String preferences_fileName,int mode)

Here preferences_fileName is the Shared Preferences file name and mode is the operational mode of the file.

The modifications over the preferences data are performed through the SharedPreferences.Editor object.

To delete the preferences data of application we call the method:

editor.remove("key"): it removes the specified key's value
editor.clear(): it removes all preferences data

The data stored in Shared preferences will lose when we perform any of the following operation:

Uninstalling the application.
Clearing the application data through setting.

Kotlin Android SharedPreferences Example

In this example, we will get the input data (id and name) from EditText and store them in a preference file. This preference data is retrieved and displayed in TextView by performing the click action on Button and make clear (remove) the preferences data.

activity_main.xml

Add the following code in the activity_main.xml layout file:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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="example.javatpoint.com.kotlinsharedpreference.MainActivity">

    <TableLayout
        android:layout_width="368dp"
        android:layout_height="495dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <TableRow>

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_column="0"
                android:layout_marginLeft="10sp"
                android:layout_marginStart="10sp"
                android:text="Enter Id"
                android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium" />

            <EditText
                android:id="@+id/editId"
                android:layout_width="201dp"
                android:layout_height="wrap_content"
                android:layout_column="1"
                android:layout_marginLeft="50sp"
                android:layout_marginStart="50sp"
                android:hint="id"
                android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium" />
        </TableRow>


        <TableRow>

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_column="0"
                android:layout_marginLeft="10sp"
                android:layout_marginStart="10sp"
                android:text="Enter Name"
                android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium" />

            <EditText
                android:id="@+id/editName"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_column="1"
                android:layout_marginLeft="50sp"
                android:layout_marginStart="50sp"
                android:hint="name"
                android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium" />
        </TableRow>

        <TableRow android:layout_marginTop="60dp">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_column="0"
                android:layout_marginLeft="10sp"
                android:layout_marginStart="10sp"
                android:text="Your Id"
                android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium" />

            <TextView
                android:id="@+id/textViewShowId"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_column="1"
                android:layout_marginLeft="50sp"
                android:layout_marginStart="50sp"
                android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium" />
        </TableRow>

        <TableRow android:layout_marginTop="20dp">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_column="0"
                android:layout_marginLeft="10sp"
                android:layout_marginStart="10sp"
                android:text="Your Name"
                android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium" />

            <TextView
                android:id="@+id/textViewShowName"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_column="1"
                android:layout_marginLeft="50sp"
                android:layout_marginStart="50sp"
                android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium" />
        </TableRow>
    </TableLayout>

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="16dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:orientation="horizontal"
        android:gravity="center"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent">

        <Button
            android:id="@+id/save"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Save" />

        <Button
            android:id="@+id/view"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="View" />

        <Button
            android:id="@+id/clear"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Clear" />
    </LinearLayout>
</android.support.constraint.ConstraintLayout>

MainActivity.kt

Add the following code in the MainActivty.kt class file. In this class, we store the shared preferences data in the form of key-value in kotlinsharedpreference.

package example.javatpoint.com.kotlinsharedpreference

import android.content.Context
import android.content.SharedPreferences
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.Button
import android.widget.EditText
import android.widget.TextView



class MainActivity : AppCompatActivity() {

    private val sharedPrefFile = "kotlinsharedpreference"

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

        val inputId = findViewById<EditText>(R.id.editId)
        val inputName = findViewById<EditText>(R.id.editName)
        val outputId = findViewById<TextView>(R.id.textViewShowId)
        val outputName = findViewById<TextView>(R.id.textViewShowName)

        val btnSave = findViewById<Button>(R.id.save)
        val btnView = findViewById<Button>(R.id.view)
        val btnClear = findViewById<Button>(R.id.clear)
        val sharedPreferences: SharedPreferences = this.getSharedPreferences(sharedPrefFile,Context.MODE_PRIVATE)
        btnSave.setOnClickListener(View.OnClickListener {
            val id:Int = Integer.parseInt(inputId.text.toString())
            val name:String = inputName.text.toString()
            val editor:SharedPreferences.Editor =  sharedPreferences.edit()
            editor.putInt("id_key",id)
            editor.putString("name_key",name)
            editor.apply()
            editor.commit()
        })
        btnView.setOnClickListener {
            val sharedIdValue = sharedPreferences.getInt("id_key",0)
            val sharedNameValue = sharedPreferences.getString("name_key","defaultname")
            if(sharedIdValue.equals(0) && sharedNameValue.equals("defaultname")){
                outputName.setText("default name: ${sharedNameValue}").toString()
                outputId.setText("default id: ${sharedIdValue.toString()}")
            }else{
                outputName.setText(sharedNameValue).toString()
                outputId.setText(sharedIdValue.toString())
            }

        }
        btnClear.setOnClickListener(View.OnClickListener {
            val editor = sharedPreferences.edit()
            editor.clear()
            editor.apply()
            outputName.setText("").toString()
            outputId.setText("".toString())
        })
    }
}

Output:

Using SharedPreferences, we can create the log-in and log-out functionality in our application by storing the state (data) of a user in the preferences file.

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