Create Realm on external storage for Android M

MainActivity.java

package apptest.realm.io.androidmtest;

import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.Environment;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;

import java.io.File;

import io.realm.Realm;
import io.realm.RealmConfiguration;

public class MainActivity extends AppCompatActivity {
    RealmConfiguration myConfig;
    Realm realm;
    final private int REQUEST_WRITE_STORAGE = 100;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        boolean hasPermission = (ContextCompat.checkSelfPermission(this,
                Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED);
        if (!hasPermission) {
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
                    REQUEST_WRITE_STORAGE);
        } else {
            openRealm();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        switch (requestCode) {
            case REQUEST_WRITE_STORAGE:
                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0
                        && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                    // permission was granted, yay! Do the
                    // contacts-related task you need to do.
                    openRealm();
                } else {

                    // permission denied, boo! Disable the
                    // functionality that depends on this permission.
                    Toast toast = Toast.makeText(this,
                            "Write permission to the external storage is needed for this app", Toast.LENGTH_LONG);
                    toast.show();
                }
                return;
            default:
                break;
        }
    }

    private void openRealm() {
        File file = getExternalFilesDir("/MyApp/Db/");

        if (!file.exists()) {
            boolean result = file.mkdir();
            Log.e("TTT", "Results: " + result);
        }
        myConfig = new RealmConfiguration.Builder(file)
                .name("test" + ".realm")
                .build();
        Realm.setDefaultConfiguration(myConfig);
        realm = Realm.getDefaultInstance();
    }
}