발생한 문제

최근 Flutter도 처음 모르는 대로 Firebase와 함께 Firestore를 사용하려고 했는데, 아래와 같은 에러가 발생했습니다.

Flutter에서 cloud_firestore를 추가하면 빌드 오류가 발생하는 경우

> com.android.builder.dexing.DexArchiveMergerException: Error while merging dex archives: 
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/0.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/1.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/4.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/5.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/6.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/7.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/8.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/9.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/10.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/11.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/12.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/13.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/14.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/15.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/16.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/17.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/18.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/19.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/20.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/21.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/22.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/23.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/24.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/25.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/26.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/27.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/28.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/29.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/30.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/31.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/32.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/33.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/34.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/35.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/36.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/37.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/38.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/39.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/40.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/41.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/42.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/43.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/44.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/45.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/46.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/47.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/48.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/49.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/50.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/51.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/52.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/53.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/54.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/55.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/56.jar
 /Volumes/workspace/flutter_fcm/client/build/app/intermediates/transforms/dexBuilder/debug/57.jar
  The number of method references in a .dex file cannot exceed 64K.
  Learn how to resolve this issue at https://developer.android.com/tools/building/multidex.html

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

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

BUILD FAILED in 18s
Gradle task assembleDebug failed with exit code 1
Exited (sigterm)

긴

원인

원인은 오류 속에 있는 The number of method references in a .dex file cannot exceed 64K.가 포인트였습니다.
Android 앱(APK) 파일에는 Dalvik Executable(DEX) 형식의 실행 가능한 바이트 코드 파일이 포함되어 있으며, 그 안에 앱을 실행하는 데 사용되는 컴파일된 코드가 있습니다.
Dalvik Executable 사양은 단일 DEX 파일에서 참조할 수 있는 총 메서드 수를 65,536으로 제한합니다.
이러한 메서드에는 Android 프레임워크 메서드, 라이브러리 메서드 및 자체 코드 메서드가 포함됩니다. 컴퓨터 과학에서 Kilo, K는 1024(또는 2^10)를 나타냅니다. 65,536은 64 X 1024와 같으므로 이 제한을 64K 참조 제한이라고 합니다.
인용구 : 64K 이상의 메소드를 사용하는 앱 설정

이번에는 cloud_firestore를 추가하여 64K 참조 제한을 초과했기 때문에이 오류가 발생한 것 같습니다.

해결 방법

해결 방법은 간단하며 Android의 앱 수준 build.gradle에 ``를 추가하기 만하면됩니다.

/android/app/build.gradle

android {
  :
    defaultConfig {
         :
        multiDexEnabled true
    }
}

만약을 위해 gradle clean 혹시 flutter run 를 실행하면 무사히 기동할 수 있었습니다!

요약

Flutter 재미있네요 MaterialDesign이면 간단하게 작성할 수 있으므로 하이브리드는 이것이 좋을 것 같은 생각이 듭니다.
단지, 역시라고 할까 이번과 같이 Android/iOS에 의존하는 문제에 걸렸을 경우에 어디가 문제인가 구분하는 것이 힘들기 때문에, kotlin과 swift도 슬슬 공부해야 할 생각이 되어 왔습니다. (한다면 옛날 자바도 했기 때문에 kotlin일까?)

참조

64K 이상의 메소드를 사용하는 앱 설정
Cloud Firestore : DexArchiveMergerException Unable to merge dex