How can I save a HashMap to Sharedpreferences in Android Kotlin?

This example demonstrates how to save a HashMap to Sharedpreferences in Android Kotlin.

Step 1 − Create a new project in Android Studio, go to File ? New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

Example

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:id="@+id/rlMain"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:layout_margin="16dp"
   android:orientation="vertical">
   <EditText
      android:id="@+id/etName"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:hint="Name"
      android:inputType="text" />
   <EditText
      android:id="@+id/etAge"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:hint="Age"
      android:inputType="number" />
   <EditText
      android:id="@+id/etGame"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:hint="Favourite game"
      android:inputType="text" />
   <Button
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_marginTop="16dp"
      android:onClick="saveLocal"
      android:text="save local" />
   <TextView
      android:id="@+id/textView"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_marginTop="20dp"
      android:textColor="@android:color/background_dark"
      android:textSize="24sp"
      android:textStyle="bold|italic" />
</LinearLayout>

Step 3 − Add the following code to src/MainActivity.kt

Example

import android.content.Context
import android.content.SharedPreferences
import android.os.Bundle
import android.view.View
import android.widget.EditText
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import org.json.JSONObject
import java.util.*
import kotlin.collections.HashMap
class MainActivity : AppCompatActivity() {
   private val mapKey = "map"
   lateinit var etName: EditText
   lateinit var etAge: EditText
   lateinit var etGame: EditText
   lateinit var textView: TextView
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
      textView = findViewById(R.id.textView)
      etName = findViewById(R.id.etName)
      etAge = findViewById(R.id.etAge)
      etGame = findViewById(R.id.etGame)
      val outputMap: Map<String, Any> = loadMap()
      if (outputMap.containsKey("name"))
      etName.setText(Objects.requireNonNull(outputMap["name"]).toString())
      if (outputMap.containsKey("age"))
      etAge.setText(Objects.requireNonNull(outputMap["age"]).toString())
      if (outputMap.containsKey("game"))
      etGame.setText(Objects.requireNonNull(outputMap["game"]).toString())
   }
   private fun loadMap(): Map<String, Any> {
      val outputMap: Map<String, Any> = HashMap()
      val pSharedPref = applicationContext.getSharedPreferences(
         "MyVariables", Context.MODE_PRIVATE
      )
      if (pSharedPref != null) {
         val jsonString = pSharedPref.getString(mapKey, JSONObject().toString())
         val jsonObject = JSONObject(jsonString)
         val keysItr = jsonObject.keys()
         while (keysItr.hasNext()) {
            val key = keysItr.next()
            outputMap[key]
         }
      }
      return outputMap
   }
   fun saveLocal(view: View) {
      val name = etName.text.toString().trim()
      val age = etAge.text.toString().trim()
      val game = etGame.text.toString().trim()
      when {
         name.isEmpty() -> {
            etName.error = "*required"
            etName.requestFocus()
         }
         age.isEmpty() -> {
            etAge.error = "*required"
            etAge.requestFocus()
         }
         game.isEmpty() -> {
            etGame.error = "*required"
            etGame.requestFocus()
         }
         else -> {
            val inputMap: MutableMap<String, Any> = HashMap()
            inputMap["name"] = name
            inputMap["age"] = age
            inputMap["game"] = game
            saveMap(inputMap)
            Toast.makeText(applicationContext, "Saved Locally!", Toast.LENGTH_SHORT).show()
            textView.text = inputMap.toString()
         }
      }
   }
   private fun saveMap(inputMap: MutableMap<String, Any>) {
      val sharedPreferences: SharedPreferences = applicationContext.getSharedPreferences(
         "MyVariables", Context.MODE_PRIVATE
      )
      val jsonObject = JSONObject(inputMap)
      val jsonString = jsonObject.toString()
      val editor: SharedPreferences.Editor = sharedPreferences.edit()
      editor.remove(mapKey).apply()
      editor.putString(mapKey, jsonString)
      editor.commit()
   }
}

Step 4 − Add the following code to androidManifest.xml

Example

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.myapplication">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click the Run icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen

Azhar

Published on 23-May-2020 12:55:02

• Related Questions & Answers
• How can I save a HashMap to Shared Preferences in Android?
• How to save ArrayList to SharedPreferences on Android?
• How do I delete SharedPreferences data for my Android App using Kotlin?
• How do I delete SharedPreferences data for my Android App?
• How to use SharedPreferences on Android to store, read and edit values using Kotlin?
• How can I validate EditText input in Android using Kotlin?
• How can I display Toast messages from a thread in Android using Kotlin?
• How can I save new Date() in MongoDB?
• How can I generate random numbers in a given range in Android using Kotlin?
• How can I remove a button or make it invisible in Android using Kotlin?
• How can I save HTML locally with JavaScript?
• How can I get the current Android SDK version programmatically using Kotlin?
• How can I use marquee text in Kotlin?
• How can I send emails using gmail from my Android application using Kotlin?
• How can I define underlined text in an Android layout xml file using Kotlin?