Flutter Force Update IOS and Android App Version

version-check.dart

//Prompt users to update app if there is a new version available
//Uses url_launcher package

import 'package:url_launcher/url_launcher.dart';

const APP_STORE_URL =
    'https://phobos.apple.com/WebObjects/MZStore.woa/wa/viewSoftwareUpdate?id=YOUR-APP-ID&mt=8';
const PLAY_STORE_URL =
    'https://play.google.com/store/apps/details?id=YOUR-APP-ID';

versionCheck(context) async {
  //Get Current installed version of app
  final PackageInfo info = await PackageInfo.fromPlatform();
  double currentVersion = double.parse(info.version.trim().replaceAll(".", ""));

  //Get Latest version info from firebase config
  final RemoteConfig remoteConfig = await RemoteConfig.instance;

  try {
    // Using default duration to force fetching from remote server.
    await remoteConfig.fetch(expiration: const Duration(seconds: 0));
    await remoteConfig.activateFetched();
    remoteConfig.getString('force_update_current_version');
    double newVersion = double.parse(remoteConfig
        .getString('force_update_current_version')
        .trim()
        .replaceAll(".", ""));
    if (newVersion > currentVersion) {
      _showVersionDialog(context);
    }
  } on FetchThrottledException catch (exception) {
    // Fetch throttled.
    print(exception);
  } catch (exception) {
    print('Unable to fetch remote config. Cached or default values will be '
        'used');
  }
}
//Show Dialog to force user to update
_showVersionDialog(context) async {
  await showDialog<String>(
    context: context,
    barrierDismissible: false,
    builder: (BuildContext context) {
      String title = "New Update Available";
      String message =
          "There is a newer version of app available please update it now.";
      String btnLabel = "Update Now";
      String btnLabelCancel = "Later";
      return Platform.isIOS
          ? new CupertinoAlertDialog(
              title: Text(title),
              content: Text(message),
              actions: <Widget>[
                FlatButton(
                  child: Text(btnLabel),
                  onPressed: () => _launchURL(Config.APP_STORE_URL),
                ),
                FlatButton(
                  child: Text(btnLabelCancel),
                  onPressed: () => Navigator.pop(context),
                ),
              ],
            )
          : new AlertDialog(
              title: Text(title),
              content: Text(message),
              actions: <Widget>[
                FlatButton(
                  child: Text(btnLabel),
                  onPressed: () => _launchURL(Config.PLAY_STORE_URL),
                ),
                FlatButton(
                  child: Text(btnLabelCancel),
                  onPressed: () => Navigator.pop(context),
                ),
              ],
            );
    },
  );
}

_launchURL(String url) async {
  if (await canLaunch(url)) {
    await launch(url);
  } else {
    throw 'Could not launch $url';
  }
}