How can I save a HashMap to Shared Preferences in Android?

This example demonstrates about How can I save a HashMap to Shared Preferences in Android.

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.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="https://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" />
</LinearLayout>

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

package app.com.sample;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
import org.json.JSONObject;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Objects;
public class MainActivity extends AppCompatActivity {
   final String mapKey = "map";
   EditText etName, etAge, etGame;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      etName = findViewById(R.id.etName);
      etAge = findViewById(R.id.etAge);
      etGame = findViewById(R.id.etGame);
      Map<String, Object> outputMap = loadMap();
      if (outputMap.containsKey("name"))
      etName.setText(Objects.requireNonNull(outputMap.get("name")).toString());
      if (outputMap.containsKey("age"))
         etAge.setText(Objects.requireNonNull(outputMap.get("age")).toString());
      if (outputMap.containsKey("game"))
         etGame.setText(Objects.requireNonNull(outputMap.get("game")).toString());
   }
   public void saveLocal(View view) {
      String name = etName.getText().toString().trim();
      String age = etAge.getText().toString().trim();
      String game = etGame.getText().toString().trim();
      if (name.isEmpty()) {
         etName.setError("*required");
         etName.requestFocus();
      } else if (age.isEmpty()) {
         etAge.setError("*required");
         etAge.requestFocus();
      } else if (game.isEmpty()) {
         etGame.setError("*required");
         etGame.requestFocus();
      } else {
         Map<String, Object> inputMap = new HashMap<>();
         inputMap.put("name", name);
         inputMap.put("age", age);
         inputMap.put("game", game);
         saveMap(inputMap);
         Toast.makeText(getApplicationContext(), "Saved Locally!", Toast.LENGTH_SHORT).show();
      }
   }
   private void saveMap(Map<String, Object> inputMap) {
      SharedPreferences pSharedPref = getApplicationContext().getSharedPreferences("MyVariables",
         Context.MODE_PRIVATE);
      if (pSharedPref != null) {
         JSONObject jsonObject = new JSONObject(inputMap);
         String jsonString = jsonObject.toString();
         SharedPreferences.Editor editor = pSharedPref.edit();
         editor.remove(mapKey).apply();
         editor.putString(mapKey, jsonString);
         editor.commit();
      }
   }
   private Map<String, Object> loadMap() {
      Map<String, Object> outputMap = new HashMap<>();
      SharedPreferences pSharedPref = getApplicationContext().getSharedPreferences("MyVariables",
         Context.MODE_PRIVATE);
      try {
         if (pSharedPref != null) {
            String jsonString = pSharedPref.getString(mapKey, (new JSONObject()).toString());
            JSONObject jsonObject = new JSONObject(jsonString);
            Iterator<String> keysItr = jsonObject.keys();
            while (keysItr.hasNext()) {
               String key = keysItr.next();
               outputMap.put(key, jsonObject.get(key));
            }
         }
      } catch (Exception e) {
         e.printStackTrace();
      }
      return outputMap;
   }
}

Step 4  − Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="https://schemas.android.com/apk/res/android"
   package="app.com.sample">
   <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 Run  Icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen –