How to set locale programmatically in android app?

This example demonstrates how do I set locale programmatically 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"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:context=".MainActivity">
   <TextView
      android:id="@+id/textView"
      android:text="@string/Have_a_nice_day"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true"
      android:textStyle="bold"
      android:textSize="24sp"/>
</RelativeLayout>

Step 3 – Create a directory (values-es) and copy the string.xml file into this directory and make the below changes

<resources>
   <string name="app_name">Sample</string>
   <string name="Have_a_nice_day">Que tengas un buen día</string>
</resources>

Step 4 − Add the following code to src/MainActivity.java

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 java.util.Locale;
public class MainActivity extends AppCompatActivity {
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setAppLocale("es");
      setContentView(R.layout.activity_main);
   }
   private void setAppLocale(String localeCode){
      Resources resources = getResources();
      DisplayMetrics displayMetrics = resources.getDisplayMetrics();
      Configuration configuration = resources.getConfiguration();
      configuration.setLocale(new Locale(localeCode.toLowerCase()));
      resources.updateConfiguration(configuration, displayMetrics);
      configuration.locale = new Locale(localeCode.toLowerCase());
      resources.updateConfiguration(configuration, displayMetrics);
   }
}

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 Mobiledevice with your computer. To run the app from android studio, open one of your project'sactivity files and click Run  icon from the toolbar. Select your mobile device as an optionand then check your mobile device which will display your default screen –

Click here to download the project code.