Flutter Firebase Analytics Android: Network upload failed (java.net.ConnectException)

[Asim Bhadra]

I'm facing an issue with Firebase Analytics event logging in my Flutter app. Events are not being logged on Android devices, although they work perfectly on iOS. The following error message appears in adb logcat:

05-27 14:55:08.562 V/FA-SVC ( 6814): Network upload failed. Will retry later. code, error: 0, java.net.ConnectException: Failed to connect to app-measurement.com/[::]:443: btlq.run(:com.google.android.gms@242013038@24.20.13 (190400-633713831):154)

Troubleshooting:

Verified Firebase Configuration: Double-checked the correct placement of GoogleService-Info.plist (iOS) or google-services.json (Android), project registration in Firebase, and ensured Analytics is enabled.
Network Connectivity: Confirmed a stable internet connection by testing on different networks.
Google Play Services: Verified version compatibility between the app and the device.
Dependency Conflicts: Resolved any conflicts using flutter pub outdated and flutter pub upgrade.
Clean Build: Cleaned and rebuilt the app with flutter clean and flutter build apk.
Firewall/Proxy: Checked for any firewall or proxy restrictions that might be blocking the connection (if applicable).
Isolation Test: Created a new Firebase project and a new Flutter project with only Analytics for testing purposes.
Environment:

Flutter Version: 3.19.6 (3.22.1) (you can mention both versions if using the channel)
Google Play Services: 4.3.15
Dependencies:
firebase_analytics: ^10.10.6
firebase_auth: ^4.19.6
firebase_core: ^2.31.1
Relevant files:

project/build.gradle

buildscript {
    ext.kotlin_version = '1.9.22'
    repositories {
        google()
        mavenCentral()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:7.4.2'
        // START: FlutterFire Configuration
        classpath 'com.google.gms:google-services:4.4.1'
        // END: FlutterFire Configuration
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

allprojects {
    repositories {
        google()
        mavenCentral()
    }
}

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

tasks.register("clean", Delete) {
    delete rootProject.buildDir
}
app/build.gradle

plugins {
    id "com.android.application"
    id("com.google.gms.google-services")
    id "kotlin-android"
    id "dev.flutter.flutter-gradle-plugin"
   
}

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

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

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

def keystoreProperties = new Properties()
def keystorePropertiesFile = rootProject.file('key.properties')
if (keystorePropertiesFile.exists()) {
    keystoreProperties.load(new FileInputStream(keystorePropertiesFile))
}

android {
    namespace "ro.test.test"
    compileSdkVersion 34
    ndkVersion flutter.ndkVersion

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    kotlinOptions {
        jvmTarget = '1.8'
    }

    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 "ro.daredigital.wishmo"
        // You can update the following values to match your application needs.
        // For more information, see: https://docs.flutter.dev/deployment/android#reviewing-the-gradle-build-configuration.
        minSdkVersion 24
        targetSdkVersion 34
        versionCode flutterVersionCode.toInteger()
        versionName flutterVersionName
        multiDexEnabled true
    }

     signingConfigs {
       release {
           keyAlias keystoreProperties['keyAlias']
           keyPassword keystoreProperties['keyPassword']
           storeFile keystoreProperties['storeFile'] ? file(keystoreProperties['storeFile']) : null
           storePassword keystoreProperties['storePassword']
       }
   }
   buildTypes {
       release {
           signingConfig signingConfigs.release
       }
   }
}

flutter {
    source '../..'
}

dependencies {
    // Import the BoM for the Firebase platform
    implementation(platform("com.google.firebase:firebase-bom:33.0.0"))
    // Add the dependency for the Analytics library
    // When using the BoM, you dopn't specify versions in Firebase library dependencies
    implementation("com.google.firebase:firebase-analytics")
}