Android Internationalization not working for some Android devices

Issue

I have an android app that targets the SDK Version 25 and the min SDK 17. This is app is supposed to be in 4 languages : French, Swahili, English and Kirundi.

But for some android devices, all four languages work properly but for some others, all other languages work except Kirundi when the user switches to it.

Here is my code:

public class LanguageSwitcher extends AppCompatActivity {

    //Variables declaration
    private TextView bdi,en,fr,sw;

    private Resources res;
    private DisplayMetrics dm;
    android.content.res.Configuration conf;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_language_switcher);


        bdi = (TextView)findViewById(R.id.bdi); //Kirundi textview
        fr  = (TextView)findViewById(R.id.fr); //francais textview
        en  = (TextView)findViewById(R.id.en); //english textview
        sw  = (TextView)findViewById(R.id.sw); //swahili textview


        res = getResources();
        dm  = res.getDisplayMetrics();
        conf= res.getConfiguration();


        //getting the sharedPreferences 
        SharedPreferences sharedPreferences=getSharedPreferences("profile", Context.MODE_PRIVATE);

        String lang = sharedPreferences.getString("lang","");

        final SharedPreferences.Editor editor = sharedPreferences.edit();

        bdi.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                conf.locale = new Locale("rn"); // API 17+ only.
                editor.putString("lang","rn");
                editor.apply();
                res.updateConfiguration(conf, dm);
                startActivity(new Intent(getApplicationContext(),Acceuil.class));
            }
        });
        fr.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                conf.locale = new Locale("fr"); // API 17+ only.
                editor.putString("lang","fr");
                editor.apply();
                res.updateConfiguration(conf, dm);
                startActivity(new Intent(getApplicationContext(),Acceuil.class));
            }
        });
        sw.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                conf.locale = new Locale("sw"); // API 17+ only.
                editor.putString("lang","sw");
                editor.apply();
                res.updateConfiguration(conf, dm);
                startActivity(new Intent(getApplicationContext(),Acceuil.class));
            }
        });
        en.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                conf.locale = new Locale("en"); // API 17+ only.
                editor.putString("lang","en");
                editor.apply();
                res.updateConfiguration(conf, dm);
                startActivity(new Intent(getApplicationContext(),Acceuil.class));
            }
        });
    }
}

I don't know where I am wrong with my code. I need your help

Solution

I made some researches and found that unlike other languages, Kirundi resources should be under res/values-rn-rBI folder instead of res/values-rn folder. rn as ISO 639-1 language code like for any other language in Android and BI the ISO 3166-1 Alpha-2 Code for the country (Burundi) and that worked.

Answered By - Gratien Asimbahwe