Flutter: build error when adding "image_cropper" and "contacts_service" packages

I can successfully build and run a fresh new flutter project. But when I add both image_cropper: ^1.0.0 and contacts_service: ^0.2.4 packages to pubspec.yaml and run flutter packages get, I cannot build the project anymore, and get this build error:

D8: Program type already present: android.support.v4.app.INotificationSideChannel

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:transformDexArchiveWithExternalLibsDexMergerForDebug'.
> com.android.builder.dexing.DexArchiveMergerException: Error while merging dex archives: E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\2.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\3.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\4.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\5.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\6.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\7.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\8.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\9.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\10.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\11.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\12.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\13.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\14.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\15.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\16.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\17.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\18.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\19.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\20.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\21.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\22.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\23.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\24.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\25.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\26.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\27.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\28.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\29.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\30.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\31.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\32.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\33.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\34.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\35.jar, E:\Projects\flutter\hello\build\app\intermediates\transforms\dexBuilder\debug\36.jar
  Learn how to resolve the issue at https://developer.android.com/studio/build/dependencies#duplicate_classes.
  Program type already present: android.support.v4.app.INotificationSideChannel

* 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 1m 19s
*******************************************************************************************
The Gradle failure may have been because of AndroidX incompatibilities in this Flutter app.
See https:///CP92wY for more information on the problem and how to fix it.
*******************************************************************************************
Finished with error: Gradle task assembleDebug failed with exit code 1

I do not understand this error very well, but it seems that there is a naming conflict between these two packages (because of duplicate_classes in the error text). Is there any workaround for this?

Note that this error does not happen with any other pair of packages for me.

Solution

This was an Android X compatibility issue. I could get it fixed by following the steps mentioned here, but in summary:

First make sure that compileSdkVersion is at least 28 in app/build.gradle. This property controls the version of the Android SDK that Gradle uses to build your APK. It doesn’t affect the minimum SDK version that your app can run on.
Right click on android directory of flutter project and open it using this menu: Flutter > Open android module in android studio
In the newly opened project, from menus select Refactor > Migrate to AdnroidX
Close the project and open your flutter project again.