flutter-rp-example/lib/utils.dart

import 'dart:io' show Platform;

import 'package:flutter/foundation.dart' show kIsWeb;
import 'package:package_info_plus/package_info_plus.dart';

String getRedirectURI() {
  if (kIsWeb) {
    // Use the current page's origin so the redirect URI always matches
    // the host and port the app is actually served on.
    final base = Uri.base;
    final port = base.hasPort ? ':${base.port}' : '';
    return '/${base.host}$port/auth.html';
  }
  try {
    if (Platform.isAndroid) {
      return "";
    } else {
      return "/localhost:8080/auth.html";
    }
  } catch (e) {
    return "/localhost:8080/auth.html";
  }
}

Future<String> getCallbackUrlScheme() async {
  if (kIsWeb) return "http";
  try {
    if (Platform.isAndroid) {
      PackageInfo packageInfo = await PackageInfo.fromPlatform();
      return packageInfo.packageName;
    } else {
      return "http";
    }
  } catch (e) {
    return "http";
  }
}