How to change app language when user selects language in Android?

This example demonstrates how do I change app language when user selects language.
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.
<RelativeLayout
   xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:id="@+id/rl"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:padding="10dp"
   tools:context=".MainActivity">
   <Spinner
      android:id="@+id/spinner"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true" />
   <TextView
      android:id="@+id/string"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="@string/thank_you"
      android:textSize="24sp"
      android:layout_centerInParent="true"
      android:layout_below="@id/spinner"/>
</RelativeLayout>
Step 3 − Add the following code to src/MainActivity.java
import android.content.Intent;
import android.content.res.Configuration;
import android.content.res.Resources;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
public class MainActivity extends AppCompatActivity {
   Spinner spinner;
   Locale locale;
   String currentLanguage = "en", currentLang;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      currentLanguage = getIntent().getStringExtra(currentLang);
      spinner = findViewById(R.id.spinner);
      List<String> list = new ArrayList<>();
      list.add("Select Language");
      list.add("English");
      list.add("Español");
      list.add("Français");
      list.add("Hindi");
      ArrayAdapter<String> adapter = new ArrayAdapter<>(this, R.layout.support_simple_spinner_dropdown_item, list);
      adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
      spinner.setAdapter(adapter);
      spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
         @Override
         public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            switch (position) {
               case 0:
               break;
               case 1:
                  setLocale("en");
               break;
               case 2:
                  setLocale("es");
               break;
               case 3:
                  setLocale("fr");
               break;
               case 4:
                  setLocale("hi");
               break;
            }
         }
         @Override
         public void onNothingSelected(AdapterView<?> parent) {
         }
      });
   }
   private void setLocale(String localeName) {
      if (!localeName.equals(currentLanguage)) {
         locale = new Locale(localeName);
         Resources res = getResources();
         DisplayMetrics dm = res.getDisplayMetrics();
         Configuration conf = res.getConfiguration();
         conf.locale = locale;
         res.updateConfiguration(conf, dm);
         Intent refresh = new Intent(this,
         MainActivity.class);
         refresh.putExtra(currentLang, localeName);
         startActivity(refresh);
      } else {
         Toast.makeText(MainActivity.this, "Language
         already selected!", Toast.LENGTH_SHORT).show();
      }
   }
   public void onBackPressed() {
      Intent intent = new Intent(Intent.ACTION_MAIN);
      intent.addCategory(Intent.CATEGORY_HOME);
      intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
      startActivity(intent);
      finish();
      System.exit(0);
   }
}
Step 4 − Create values-es, values-fr, values-hi and add the following code −
values-hi/strings.xml
<resources>
   <string name="app_name">Sample</string>
   <string name="thank_you">धन्यवाद</string>
</resources>
values-fr/strings.xml
<resources>
   <string name="app_name">Sample</string>
   <string name="thank_you">Je vous remercie</string>
</resources>
values-es/strings.xml
<resources>
   <string name="app_name">Sample</string>
   <string name="thank_you">Gracias</string>
</resources>
strings.xml
<resources>
   <string name="app_name">Sample</string>
   <string name="thank_you">Thank you</string>
</resources>
Step 5 − Add the following code to androidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest
   xmlns:android="http://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 −