Change app language programmatically in Android

It's possible. You can set the locale. However, I would not recommend that. We've tried it at early stages, it's basically fighting the system.

We have the same requirement for changing the language but decided to settle to the fact that UI should be same as phone UI. It was working via setting locale but was too buggy. And you have to set it every time you enter activity (each activity) from my experience. here is a code if you still need this (again, I don't recommend that)

Resources res = context.getResources();// Change locale settings in the app.DisplayMetrics dm = res.getDisplayMetrics();android.content.res.Configuration conf = res.getConfiguration();conf.setLocale(new Locale(language_code.toLowerCase())); // API 17+ only.// Use conf.locale = new Locale(...) if targeting lower versionsres.updateConfiguration(conf, dm);

If you have language specific content - you can change that base on the setting.

update on 26th of march 2020

    public static void setLocale(Activity activity, String languageCode) {        Locale locale = new Locale(languageCode);        Locale.setDefault(locale);        Resources resources = activity.getResources();        Configuration config = resources.getConfiguration();        config.setLocale(locale);        resources.updateConfiguration(config, resources.getDisplayMetrics());    }

• NOTES: Language code cannot got '-' & must be 2 small case letter only

This code really works:

fa = Persian, en = English

• NOTES: Language code cannot got '-' & must be 2 small case letter only

Enter your language code in languageToLoad variable:

import android.app.Activity;import android.content.res.Configuration;import android.os.Bundle;public class Main extends Activity {  /** Called when the activity is first created. */  @Override  public void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    String languageToLoad  = "fa"; // your language    Locale locale = new Locale(languageToLoad);     Locale.setDefault(locale);    Configuration config = new Configuration();    config.locale = locale;    getBaseContext().getResources().updateConfiguration(config,       getBaseContext().getResources().getDisplayMetrics());    this.setContentView(R.layout.main);  }}

UPDATE on Jun 2021(Kotlin):

class Main : Activity() {    // Called when the activity is first created.    public override fun onCreate(savedInstanceState: Bundle?) {        super.onCreate(savedInstanceState)                val config = resources.configuration        val lang = "fa" // your language code        val locale = Locale(lang)        Locale.setDefault(locale)        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1)            config.setLocale(locale)        else            config.locale = locale        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N)            createConfigurationContext(config)        resources.updateConfiguration(config, resources.displayMetrics)        this.setContentView(R.layout.main)    }}

I was looking for a way to change the system language programmatically.While I fully understand that a normal application should never do that and instead either:

• the user should be pointed(through an intent) to the system settings to change it manually
• the application should handle its localization on its own just like described in the answer of Alex

there was a need to really change the language of the system programmtically.

This is undocumented API and thus should not be used for market/end-user applications!

Anyway heres the solution i found:

  Locale locale = new Locale(targetLocaleAsString);  Class amnClass = Class.forName("android.app.ActivityManagerNative");  Object amn = null;  Configuration config = null;  // amn = ActivityManagerNative.getDefault();  Method methodGetDefault = amnClass.getMethod("getDefault");  methodGetDefault.setAccessible(true);  amn = methodGetDefault.invoke(amnClass);  // config = amn.getConfiguration();  Method methodGetConfiguration = amnClass.getMethod("getConfiguration");  methodGetConfiguration.setAccessible(true);  config = (Configuration) methodGetConfiguration.invoke(amn);  // config.userSetLocale = true;  Class configClass = config.getClass();  Field f = configClass.getField("userSetLocale");  f.setBoolean(config, true);  // set the locale to the new value  config.locale = locale;  // amn.updateConfiguration(config);  Method methodUpdateConfiguration = amnClass.getMethod("updateConfiguration", Configuration.class);  methodUpdateConfiguration.setAccessible(true);  methodUpdateConfiguration.invoke(amn, config);