Flutter Web - No Firebase App '[DEFAULT]' has been created - call Firebase App.initializeApp() (app/no-app)

Question

I understand there are many very similar questions to this; but none of their solutions work for me. I've tried them all. PS: I expect the problem is something to do with my index.html

Problem: I am using Firebase (on Flutter web) and I am trying to authenticate users through it. However, my site won't even launch (blank screen) after I tried adding Firebase to it to get it to work. I'd appreciate some help figuring this out!

The Error: No Firebase App '[DEFAULT]' has been created - call Firebase App.initializeApp() (app/no-app)

Notes: The problem occurs on Flutter web but works on my Android phone. Also, I have spent hours looking up every answer to all similar questions and none of their solutions work. Additionally, this is my first time asking a question, so please let me know if I'm doing anything wrong. Thanks!

Output for Error:

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FirebaseError: Firebase: No Firebase App '[DEFAULT]' has been created - call Firebase App.initializeApp()
(app/no-app).
    at Object.u [as app] (https://www.gstatic.com/firebasejs/8.4.3/firebase-app.js:1:18229)
    at Object.app$ [as app]
    (http://localhost:60058/packages/firebase_core_web/src/interop/core.dart.lib.js:42:101)
    at new cloud_firestore_web.FirebaseFirestoreWeb.new
    (http://localhost:60058/packages/cloud_firestore_web/src/write_batch_web.dart.lib.js:865:64)
    at Function.registerWith
    (http://localhost:60058/packages/cloud_firestore_web/src/write_batch_web.dart.lib.js:788:73)
    at Object.registerPlugins
    (http://localhost:60058/packages/chat/generated_plugin_registrant.dart.lib.js:30:46)
    at main (http://localhost:60058/web_entrypoint.dart.lib.js:44:35)
    at main.next (<anonymous>)
    at runBody (http://localhost:60058/dart_sdk.js:39051:34)
    at Object._async [as async] (http://localhost:60058/dart_sdk.js:39082:7)
    at main$ (http://localhost:60058/web_entrypoint.dart.lib.js:43:18)
    at http://localhost:60058/main_module.bootstrap.js:19:10
    at Array.forEach (<anonymous>)
    at window.$dartRunMain (http://localhost:60058/main_module.bootstrap.js:18:32)
    at <anonymous>:1:8
    at Object.runMain (http://localhost:60058/dwds/src/injected/client.js:8656:21)
    at http://localhost:60058/dwds/src/injected/client.js:22068:19
    at _wrapJsFunctionForAsync_closure.$protected
    (http://localhost:60058/dwds/src/injected/client.js:3830:15)
    at _wrapJsFunctionForAsync_closure.call$2 (http://localhost:60058/dwds/src/injected/client.js:10905:12) 
    at Object._asyncStartSync (http://localhost:60058/dwds/src/injected/client.js:3794:20)
    at main__closure1.$call$body$main__closure (http://localhost:60058/dwds/src/injected/client.js:22080:16)    at main__closure1.call$1 (http://localhost:60058/dwds/src/injected/client.js:22007:19)
    at StaticClosure._rootRunUnary [as call$2$5]
    (http://localhost:60058/dwds/src/injected/client.js:4153:16)
    at _CustomZone.runUnary$2$2 (http://localhost:60058/dwds/src/injected/client.js:12136:39)
    at _CustomZone.runUnaryGuarded$1$2 (http://localhost:60058/dwds/src/injected/client.js:12068:14)        
    at _ControllerSubscription._sendData$1 (http://localhost:60058/dwds/src/injected/client.js:11697:19)    
    at _DelayedData.perform$1 (http://localhost:60058/dwds/src/injected/client.js:11849:59)
    at _PendingEvents_schedule_closure.call$0 (http://localhost:60058/dwds/src/injected/client.js:11898:14) 
    at Object._microtaskLoop (http://localhost:60058/dwds/src/injected/client.js:3990:24)
    at StaticClosure._startMicrotaskLoop (http://localhost:60058/dwds/src/injected/client.js:3996:11)       
    at _AsyncRun__initializeScheduleImmediate_internalCallback.call$1
    (http://localhost:60058/dwds/src/injected/client.js:10774:9)
    at invokeClosure (http://localhost:60058/dwds/src/injected/client.js:1250:26)
    at MutationObserver.<anonymous> (http://localhost:60058/dwds/src/injected/client.js:1269:18)

My entire index.html file (some fields I've blurred with "X"s because I'm not sure if they're personal details):

<!DOCTYPE html>
<html>
<head>
  <!--
    If you are serving your web app in a path other than the root, change the
    href value below to reflect the base path you are serving from.
    The path provided below has to start and end with a slash "/" in order for
    it to work correctly.
    Fore more details:
    * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/base
  -->
  <base href="/">

  <meta charset="UTF-8">
  <meta content="IE=Edge" http-equiv="X-UA-Compatible">
  <meta name="description" content="A new Flutter project.">

  <!-- iOS meta tags & icons -->
  <meta name="apple-mobile-web-app-capable" content="yes">
  <meta name="apple-mobile-web-app-status-bar-style" content="black">
  <meta name="apple-mobile-web-app-title" content="chat">
  <link rel="apple-touch-icon" href="icons/Icon-192.png">

  <!-- Favicon -->
  <link rel="icon" type="image/png" href="favicon.png"/>

  <title>chat</title>
  <link rel="manifest" href="manifest.json">
</head>
<body>
  <!-- Insert these scripts at the bottom of the HTML, but before you use any Firebase services -->

  <!-- Firebase App (the core Firebase SDK) is always required and must be listed first -->
  <script src="https://www.gstatic.com/firebasejs/8.4.3/firebase-app.js"></script>

  <!-- If you enabled Analytics in your project, add the Firebase SDK for Analytics -->
  <script src="https://www.gstatic.com/firebasejs/8.4.3/firebase-analytics.js"></script>

  <!-- Add Firebase products that you want to use -->
  <script src="https://www.gstatic.com/firebasejs/8.4.3/firebase-auth.js"></script>
  <script src="https://www.gstatic.com/firebasejs/8.4.3/firebase-firestore.js"></script>
  <!-- This script installs service_worker.js to provide PWA functionality to
       application. For more information, see:
       https://developers.google.com/web/fundamentals/primers/service-workers -->
       <script>
        // TODO: Replace the following with your app's Firebase project configuration
        // For Firebase JavaScript SDK v7.20.0 and later, `measurementId` is an optional field
        var firebaseConfig = {
          // ...
        };
        const firebaseConfig = {
    apiKey: "XX",
    authDomain: "X",
    projectId: "chat-6052e",
    storageBucket: "XXXXX",
    messagingSenderId: "XXX",
    appId: "XX"
  };
        // Initialize Firebase
        firebase.initializeApp(firebaseConfig);
      </script>
  <script>
    if ('serviceWorker' in navigator) {
      window.addEventListener('flutter-first-frame', function () {
        navigator.serviceWorker.register('flutter_service_worker.js');
      });
    }
  </script>
  
  <script src="main.dart.js" type="application/javascript"></script>
</body>
</html>

My main.dart function (the start of it showing I have initalized Firebase like many of the other answers say is the solution):

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}

My pubspec.yaml (some of it showing dependencies):

dependencies:
  flutter:
    sdk: flutter


  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^1.0.2
  google_fonts: ^2.0.0
  firebase_core: ^1.1.0
  firebase_auth: ^1.1.2
  google_sign_in: ^5.0.2
  email_validator: '^1.0.6'
  provider: ^5.0.0
  cloud_firestore: ^1.0.7

dev_dependencies:
  flutter_test:
    sdk: flutter

Build gradle (entire thing):

buildscript {
    ext.kotlin_version = '1.3.50'
    repositories {
        google()
        jcenter()
    }

    dependencies {
        classpath 'com.google.gms:google-services:4.3.5' // was 4.3.5
        classpath 'com.android.tools.build:gradle:4.1.0'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

allprojects {
    repositories {
        google()
        jcenter()
    }
}

rootProject.buildDir = '../build'
subprojects {
    project.buildDir = "${rootProject.buildDir}/${project.name}"
}
subprojects {
    project.evaluationDependsOn(':app')
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

App-level build gradle (entire thing):

def localProperties = new Properties()
def localPropertiesFile = rootProject.file('local.properties')
if (localPropertiesFile.exists()) {
    localPropertiesFile.withReader('UTF-8') { reader ->
        localProperties.load(reader)
    }
}

def flutterRoot = localProperties.getProperty('flutter.sdk')
if (flutterRoot == null) {
    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
}

def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
if (flutterVersionCode == null) {
    flutterVersionCode = '1'
}

def flutterVersionName = localProperties.getProperty('flutter.versionName')
if (flutterVersionName == null) {
    flutterVersionName = '1.0'
}

apply plugin: 'com.google.gms.google-services'
apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"

android {
    compileSdkVersion 30

    sourceSets {
        main.java.srcDirs += 'src/main/kotlin'
    }

    defaultConfig {
        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
        applicationId "com.example.chat"
        minSdkVersion 21 // was 16
        targetSdkVersion 30
        versionCode flutterVersionCode.toInteger()
        versionName flutterVersionName
    }

    buildTypes {
        release {
            // TODO: Add your own signing config for the release build.
            // Signing with the debug keys for now, so `flutter run --release` works.
            signingConfig signingConfigs.debug
        }
    }
}

flutter {
    source '../..'
}

dependencies {
    implementation platform('com.google.firebase:firebase-bom:27.1.0')
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
}

Answer 1

Solution

So after a few more hours of messing around, I determined that my index.html file was the problem.

Copy the file below and replace your index.html with it, but change the fields with XXX's (they're unique to you I believe):

<!DOCTYPE html>
<html>
<head>
  <!--
    If you are serving your web app in a path other than the root, change the
    href value below to reflect the base path you are serving from.
    The path provided below has to start and end with a slash "/" in order for
    it to work correctly.
    Fore more details:
    * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/base
  -->
  <base href="/">

  <meta charset="UTF-8">
  <meta content="IE=Edge" http-equiv="X-UA-Compatible">
  <meta name="description" content="A new Flutter project.">

  <!-- iOS meta tags & icons -->
  <meta name="apple-mobile-web-app-capable" content="yes">
  <meta name="apple-mobile-web-app-status-bar-style" content="black">
  <meta name="apple-mobile-web-app-title" content="chat">
  <link rel="apple-touch-icon" href="icons/Icon-192.png">

  <!-- Favicon -->
  <link rel="icon" type="image/png" href="favicon.png"/>

  <title>chat</title>
  <link rel="manifest" href="manifest.json">
</head>
<body>
  <!-- Insert these scripts at the bottom of the HTML, but before you use any Firebase services -->

  <!-- Firebase App (the core Firebase SDK) is always required and must be listed first -->
  <script src="https://www.gstatic.com/firebasejs/8.4.3/firebase-app.js"></script>

  <!-- If you enabled Analytics in your project, add the Firebase SDK for Analytics -->
  <script src="https://www.gstatic.com/firebasejs/8.4.3/firebase-analytics.js"></script>

  <!-- Add Firebase products that you want to use -->
  <script src="https://www.gstatic.com/firebasejs/8.4.3/firebase-auth.js"></script>
  <script src="https://www.gstatic.com/firebasejs/8.4.3/firebase-firestore.js"></script>
  <!-- This script installs service_worker.js to provide PWA functionality to
       application. For more information, see:
       https://developers.google.com/web/fundamentals/primers/service-workers -->
       <script>
        // TODO: Replace the following with your app's Firebase project configuration
        // For Firebase JavaScript SDK v7.20.0 and later, `measurementId` is an optional field
        var firebaseConfig = {
          apiKey: "XXX",
    authDomain: "XXX",
    projectId: "XXX",
    storageBucket: "XXX",
    messagingSenderId: "XXX",
    appId: "XXX"
        };
        
        // Initialize Firebase
        firebase.initializeApp(firebaseConfig);
      </script>
  <script>
    if ('serviceWorker' in navigator) {
      window.addEventListener('flutter-first-frame', function () {
        navigator.serviceWorker.register('flutter_service_worker.js');
      });
    }
  </script>
  
  <script src="main.dart.js" type="application/javascript"></script>
</body>
</html>