Shared Preferences With Kotlin

In this tutorial, we are going to learn how to use SharedPreferences In our Android Application to Store data in the form of value-key pairs with a simple Kotlin class.

Here w are going to learn how to create a simple custom SharedPreferences.kt class that can be used to every Android application if needed.

Overview

In many cases, we have to use SharedPreferences in our Application such as to store login status, save user-specific data and save application settings.

SharedPreferences is Application specific, so data stored in SharedPreferences can be lost in the following situations

By Uninstalling the Application
By Clearing application data (Using device settings)

Storing Data with SharedPreferences

Let’s start with the custom SharedPreference.kt class. Create a Kotlin class And Initialise SharedPreferences as shown below.

package com.kotlincodes.sharedpreferenceswithkotlin

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

/**
 * Created by Kolincodes on 10/05/2018.
 */

class SharedPreference(val context: Context) {
    private val PREFS_NAME = "kotlincodes"
    val sharedPref: SharedPreferences = context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE)

}

PREF_NAME is the name of preference file.

Storing Data

To store String, Int and Boolean data we have three methods with the same name and different parameters (Method overloading). Add these methods to your SharedPreference.kt class.

To Store String data

 
 fun save(KEY_NAME: String, value: Int) {
        val editor: SharedPreferences.Editor = sharedPref.edit()

        editor.putInt(KEY_NAME, value)

        editor.commit()
    }

To Store Int data

  
  fun save(KEY_NAME: String, value: Int) {
        val editor: SharedPreferences.Editor = sharedPref.edit()

        editor.putInt(KEY_NAME, value)

        editor.commit()
    }

To Store Boolean data

 
 fun save(KEY_NAME: String, status: Boolean) {

        val editor: SharedPreferences.Editor = sharedPref.edit()

        editor.putBoolean(KEY_NAME, status!!)

        editor.commit()
    }

Retrieve Data

To Retrieve the data stored in SharedPreferences use the following methods.

To Retrieve String

 
 fun getValueString(KEY_NAME: String): String? {

        return sharedPref.getString(KEY_NAME, null)
    }

To Retrieve Int

fun getValueInt(KEY_NAME: String): Int {

        return sharedPref.getInt(KEY_NAME, 0)
    }

To Retrieve Boolien

 
 fun getValueString(KEY_NAME: String): String? {

        return sharedPref.getString(KEY_NAME, null)
    }

Remove and Clear

To clear the entire SharedPreferences use the below code

 
 fun clearSharedPreference() {

        val editor: SharedPreferences.Editor = sharedPref.edit()

        //sharedPref = PreferenceManager.getDefaultSharedPreferences(context);

        editor.clear()
        editor.commit()
    }

To remove a specific data

 
 fun removeValue(KEY_NAME: String) {

        val editor: SharedPreferences.Editor = sharedPref.edit()

        editor.remove(KEY_NAME)
        editor.commit()
    }

Now we are almost done with all the methods inside our SharedPreference.kt class.
Please find the Complete code for SharedPreference.kt file below.

SharedPreference.kt

package com.kotlincodes.sharedpreferenceswithkotlin

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

/**
 * Created by Kolincodes on 10/05/2018.
 */

class SharedPreference(val context: Context) {
    private val PREFS_NAME = "kotlincodes"
    val sharedPref: SharedPreferences = context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE)

    fun save(KEY_NAME: String, text: String) {

        val editor: SharedPreferences.Editor = sharedPref.edit()

        editor.putString(KEY_NAME, text)

        editor!!.commit()
    }

    fun save(KEY_NAME: String, value: Int) {
        val editor: SharedPreferences.Editor = sharedPref.edit()

        editor.putInt(KEY_NAME, value)

        editor.commit()
    }

    fun save(KEY_NAME: String, status: Boolean) {

        val editor: SharedPreferences.Editor = sharedPref.edit()

        editor.putBoolean(KEY_NAME, status!!)

        editor.commit()
    }

    fun getValueString(KEY_NAME: String): String? {

        return sharedPref.getString(KEY_NAME, null)


    }

    fun getValueInt(KEY_NAME: String): Int {

        return sharedPref.getInt(KEY_NAME, 0)
    }

    fun getValueBoolien(KEY_NAME: String, defaultValue: Boolean): Boolean {

        return sharedPref.getBoolean(KEY_NAME, defaultValue)

    }

    fun clearSharedPreference() {

        val editor: SharedPreferences.Editor = sharedPref.edit()

        //sharedPref = PreferenceManager.getDefaultSharedPreferences(context);

        editor.clear()
        editor.commit()
    }

    fun removeValue(KEY_NAME: String) {

        val editor: SharedPreferences.Editor = sharedPref.edit()

        editor.remove(KEY_NAME)
        editor.commit()
    }
}

Implement in our Application

Now we are going to implement our SharedPreference.kt class in a Simple Android Application.

The Image below Shows the Final output of the project

Setup Layout

The Layout for our MainActivity.kt class is shown below.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_margin="12dp"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/edt_name"
        android:layout_margin="6dp"
        android:hint="Name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"

        />
    <EditText
        android:id="@+id/edt_email"
        android:layout_margin="6dp"
        android:hint="Email"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"

        />
    <LinearLayout
        android:layout_marginTop="12dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <Button
            android:id="@+id/btn_save"
            android:layout_weight="1"
            android:text="Save"
            android:layout_width="0dp"
            android:layout_height="wrap_content" />
        <Button
            android:id="@+id/btn_retriev"
            android:layout_weight="1"
            android:text="Retrieve"
            android:layout_width="0dp"
            android:layout_height="wrap_content" />
        <Button
            android:id="@+id/btn_clear"
            android:layout_weight="1"
            android:text="Clear"
            android:layout_width="0dp"
            android:layout_height="wrap_content" />

    </LinearLayout>
</LinearLayout>

Setup MainActivity

Our Application have only one page with two EditText and Three Button.

First we Initialize our SharedPreferece.kt class in our MainActivity by

val sharedPreference:SharedPreference=SharedPreference(this)

On Save button click We stores EditText values into SharedPreferences.

On Retrieve Button click we Retrieve the saved data from SharedPreferences and set this data as the EditText hint.

On Clear button click we clear all the data from shared preferences.

Our MainActivity.kt class is given below.

package com.kotlincodes.sharedpreferenceswithkotlin

import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import android.widget.Toast

class MainActivity : AppCompatActivity() {

    lateinit var edtName:EditText
    lateinit var edtEmail:EditText
    lateinit var btnSave:Button
    lateinit var btnRetrive:Button
    lateinit var btnClear:Button
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val sharedPreference:SharedPreference=SharedPreference(this)

        edtName=findViewById(R.id.edt_name)
        edtEmail=findViewById(R.id.edt_email)
        btnClear=findViewById(R.id.btn_clear)
        btnSave=findViewById(R.id.btn_save)
        btnRetrive=findViewById(R.id.btn_retriev)

        btnSave.setOnClickListener {

            val name=edtName.editableText.toString()
            val email=edtEmail.editableText.toString()
            sharedPreference.save("name",name)
            sharedPreference.save("email",email)
            Toast.makeText(this@MainActivity,"Data Stored",Toast.LENGTH_SHORT).show()
            //to save an Int
//            sharedPreference.save("intval",1)

            //to save boolien
//            sharedPreference.save("bool",true)
            
        }
        btnRetrive.setOnClickListener {
            if (sharedPreference.getValueString("name")!=null) {
                edtName.hint = sharedPreference.getValueString("name")!!
                Toast.makeText(this@MainActivity,"Data Retrieved",Toast.LENGTH_SHORT).show()
            }else{
                edtName.hint="NO value found"
            }
            if (sharedPreference.getValueString("email")!=null) {
                edtEmail.hint = sharedPreference.getValueString("email")!!
            }else{
                edtEmail.hint="No value found"
            }


        }

        btnClear.setOnClickListener {
            sharedPreference.clearSharedPreference()
            Toast.makeText(this@MainActivity,"Data Cleared",Toast.LENGTH_SHORT).show()
        }
    }
}

That’s it! Now run the project!

The full source code is available here.

kotlincodes/Shared-Preference-With-Kotlin

Contribute to kotlincodes/Shared-Preference-With-Kotlin development by creating an account on GitHub.

Thanks for reading!

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