Flutter: Adding App Update Dialog for iOS and Android

Question

I am currently working on Notification Feature so when a new Update is availible the User gets a Dialog where he can choose to Update or not. I'm doing it with Firebase Remote Config where i have a Parameter called "force_update_current_version" where i then add the Value for the Version for checking. But I do get following errors.

Thanks for your help and i wish you a healty start into the new Year.

Main.dart Code

import 'checkUpdate.dart';

@override
void initState() {
  try {
    versionCheck(**context**);
  } catch (e) {
    print(e);
  }
  **super**.initState();
}

context error: Undefined name 'context'. Try correcting the name to one that is defined, or defining the name.

super error: Invalid context for 'super' invocation.

checkUpdate.dart Code

import 'package:flutter/material.dart';
import 'dart:io';
import 'package:firebase_remote_config/firebase_remote_config.dart';
import 'package:url_launcher/url_launcher.dart';
import 'package:package_info/package_info.dart';
import 'package:flutter/cupertino.dart';

const APP_STORE_URL = 'https://apps.apple.com/us/app/appname/idAPP-ID';
const PLAY_STORE_URL =
    'https://play.google.com/store/apps/details?id=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(
    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: [
                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: [
                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';
  }
}

Config Error for App and Play Store: Undefined name 'Config'. Try correcting the name to one that is defined, or defining the name.

user_9367299 · Answer

In checkUpdate.dart we need to import the firebase_remote_config package that exposes the RemoteConfig class:

import 'package:firebase_remote_config/firebase_remote_config.dart';

Make sure to install it before.

The versionCheck() function shall be invoked from a StatefulWidget, hence, a good place to call it would be inside the first screen Widget, for example:


class FirstScreen extends StatefulWidget {
  const FirstScreen({ Key key }) : super(key: key);

  @override
  _FirstScreenState createState() => _FirstScreenState();
}

class _FirstScreenState extends State {
  @override
  void initState() {
     super.initState();
     WidgetsBinding.instance
      .addPostFrameCallback((_) => versionCheck(context));
  }
  @override
  Widget build(BuildContext context) {
    return Container(color: const Color(0xFFFFE306));
  }
}

Flutter: Adding App Update Dialog for iOS and Android

1 Answers