fetchWelcome method

 /**
     * Fetch a welcome message from the Remote Config service, and then activate it.
     */
    private void fetchWelcome() {
        mWelcomeTextView.setText(mFirebaseRemoteConfig.getString(LOADING_PHRASE_CONFIG_KEY));

        // [START fetch_config_with_callback]
        mFirebaseRemoteConfig.fetchAndActivate()
                .addOnCompleteListener(this, new OnCompleteListener<Boolean>() {
                    @Override
                    public void onComplete(@NonNull Task<Boolean> task) {
                        if (task.isSuccessful()) {
                            boolean updated = task.getResult();
                            Log.e(TAG, "Config params updated: " + updated);
                        } else {
                            Toast.makeText(MainActivity.this, "Fetch failed",
                                    Toast.LENGTH_SHORT).show();
                        }
                        displayWelcomeMessage();
                    }
                });
    }