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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
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