// Prompt for the username
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("Votre nom d'utilisateur");

        // Set up the input         TODO: style
        final EditText input = new EditText(this);
        input.setInputType(InputType.TYPE_CLASS_TEXT);
        builder.setView(input);

        // Set up the buttons
        builder.setNegativeButton("Défaut", (dialog, which) -> {
            newUser.setUserName("UserNameOf_" + uId);
            postAndSyncUser(newUser);
        });
        builder.setPositiveButton("OK", (dialog, which) -> {

            if(input.getText().toString().length() > 0 ) {
                // TODO: intégrer une vérification pour que les 'userName' soient uniques?
                newUser.setUserName(input.getText().toString());
            } else {
                newUser.setUserName("UserNameOf_" + uId);
            }
            postAndSyncUser(newUser);
        });

        // Show dialog
        AlertDialog dialog = builder.create();
        dialog.setOnShowListener(d -> {
            InputMethodManager inM = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
            inM.showSoftInput(input, InputMethodManager.SHOW_IMPLICIT);
        });
        dialog.show();