Duplicate class com.google.common.util.concurrent.ListenableFuture found in modules jetified-guava-26.0-android.jar

After updating Firebase, I encountered this issue as well.

Fix the conflict by adding the following package to your build.gradle

implementation 'com.google.guava:listenablefuture:9999.0-empty-to-avoid-conflict-with-guava'

I am using latest version of firebase firestore i.e.

implementation 'com.google.firebase:firebase-firestore:21.4.3'

and adding this line worked for me:

implementation 'com.google.guava:guava:27.0.1-android'

I think part of the issue is that Android Studio (or maybe the Gradle Plugin, however that is handled) is recommending to update the version of the Firestore dependency to 21.4.1 (likely depends on the order of repositories in your build.gradle - not sure on that). And yes, it seems that 21.4.1 causes the issue.

So yeah, just ignore that recommendation and leave it at 21.4.0. Also...

1. Firebase Docs show 21.4.0 as the correct version.
2. MVN Repository shows 21.4.1 as the latest release.
3. Google Maven Repo also lists 21.4.1 as the latest release.

For the one who does not find a solution, this helped me. Add this dependency in your app/build.gradle file.

implementation "com.google.guava:listenablefuture:9999.0-empty-to-avoid-conflict-with-guava"

Source: https://github.com/firebase/firebase-android-sdk/issues/1320#issuecomment-601159166

If you have not added firestore as a dependency and still getting this error add below dependency to gradle

implementation group: 'com.google.guava', name: 'guava', version: '27.0.1-android'

The latest version of firestore is:

implementation 'com.google.firebase:firebase-firestore:21.4.0'

implementation 'com.google.guava:guava:28.2-android'

add this to your gradle and you're good to go

I just added

implementation group: 'com.google.guava', name: 'guava', version: '27.0.1-android'

into my dependencies.