Flutter google_sign_in error : Unable to merge dex

Question

Dear Flutter community,

I am banging my head on a seemingly simple task. I want to add firebase authentication to my app. It worked on iOS but as I tried to implement it for android, I systematically get the error :

Launching lib/main.dart on Android SDK built for x86 in debug mode... Initializing gradle... Resolving dependencies... Running 'gradlew assembleDebug'... Configuration 'compile' in project ':app' is deprecated. Use 'implementation' instead. registerResGeneratingTask is deprecated, use registerGeneratedFolders(FileCollection) registerResGeneratingTask is deprecated, use registerGeneratedFolders(FileCollection) registerResGeneratingTask is deprecated, use registerGeneratedFolders(FileCollection) Configuration 'compile' in project ':google_sign_in' is deprecated. Use 'implementation' instead.

FAILURE: Build failed with an exception.

• What went wrong: Execution failed for task ':app:transformDexArchiveWithExternalLibsDexMergerForDebug'.

  java.lang.RuntimeException: java.lang.RuntimeException: com.android.builder.dexing.DexArchiveMergerException: Unable to merge dex

• Try: Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

• Get more help at https://help.gradle.org

BUILD FAILED in 34s Finished with error: Gradle build failed: 1

I reproduced the error using 'flutter create' then adding Firebase capabilities following the codelab https://codelabs.developers.google.com/codelabs/flutter-firebase/#4

Here is the only modification to pubspec.yaml

dependencies:
  flutter:
    sdk: flutter
  google_sign_in: 0.3.1 # ONLY MODIFICATION
  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^0.1.0

general build.gradle:

buildscript {
    repositories {
        google()
        jcenter()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:3.0.1'
        classpath 'com.google.gms:google-services:3.1.0' #ONLY MODIF
    }

}

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 build.gradle :

def localProperties = new Properties()
def localPropertiesFile = rootProject.file('local.properties')
if (localPropertiesFile.exists()) {
    localPropertiesFile.withInputStream { stream ->
        localProperties.load(stream)
    }
}

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.")
}

apply plugin: 'com.android.application'
apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"

android {
    compileSdkVersion 26
    buildToolsVersion '26.0.3'

    lintOptions {
        disable 'InvalidPackage'
    }

    defaultConfig {
        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
        applicationId "com.mycompany.test"
        minSdkVersion 16
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }

    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 {
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.1'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'

}

apply plugin: 'com.google.gms.google-services'

here is the flutter doctor output :

[✓] Flutter (on Mac OS X 10.13.2 17C88, locale fr-BE, channel master) • Flutter at /Users/sergebesnard/flutter • Framework revision 4d2c2aaaa1 (6 days ago), 2017-12-27 07:30:31 -0800 • Engine revision 7c126001d8 • Tools Dart version 1.25.0-dev.11.0 • Engine Dart version 2.0.0-edge.9e8a3e2d31621c1bdf6139d068e7898a2ac2ab5a

[✓] Android toolchain - develop for Android devices (Android SDK 27.0.2) • Android SDK at /Users/sergebesnard/Library/Android/sdk • Android NDK location not configured (optional; useful for native profiling support) • Platform android-27, build-tools 27.0.2 • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b08)

[✓] iOS toolchain - develop for iOS devices (Xcode 9.2) • Xcode at /Applications/Xcode.app/Contents/Developer • Xcode 9.2, Build version 9C40b • ios-deploy 1.9.2 • CocoaPods version 1.3.1

[✓] Android Studio (version 3.0) • Android Studio at /Applications/Android Studio.app/Contents • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b08)

[✓] IntelliJ IDEA Community Edition (version 2017.2.5) • Flutter plugin version 18.0 • Dart plugin version 172.4155.35

[✓] Connected devices • Android SDK built for x86 • emulator-5554 • android-x86 • Android 8.0.0 (API 26) (emulator)

I am obviously new to Android development, and would prefer not to have to become expert to get the tutorial working. Every solution I found required tinkering with the .gradle files and only apply to react-native.

Thank you for your help !

Answer 1

I had the same problem I ve added on my App/build.gradle on android/defaultConfig the line :

    multiDexEnabled true

and on dependencies

    implementation 'androidx.multidex:multidex:2.0.1'

App/build.gradle look like this:

def localProperties = new Properties()
...

android {
    compileSdkVersion 28

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

    lintOptions {
        disable 'InvalidPackage'
    }

    defaultConfig {
        ....
        versionName flutterVersionName
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        multiDexEnabled true
    }


flutter {
    source '../..'
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    .....
    implementation 'androidx.multidex:multidex:2.0.1'
}

it works for me

Answer 2

I also had the same issue and I read that you had to include multiDexEnabled true in the app\build.gradle defaultConfig section. This worked for me.