How do I resolve "Duplicate files copied in APK META-INF/*"

I am working at a commercial android application. I am also using some libraries licensed under different license types some of them stating the following:

If the library has a "NOTICE" file with attribution notes, you must include that NOTICE when you distribute

(One of them is licensed under Apache License 2.0 for example).

There is more than one library. When I do the build with gradle or with Android Studio I obtain the following build error:

* What went wrong:
Execution failed for task ':app:transformResourcesWithMergeJavaResForDebug'.
> com.android.build.api.transform.TransformException: com.android.builder.packaging.DuplicateFileException: Duplicate files copied in APK META-INF/license.txt

The answers that I found until now on the internet and stackoverflow suggest to remove the license.txt(notice.txt or other files that could interfere like this) from packaging by adding to build.gradle file the following:

packagingOptions {
    exclude 'META-INF/DEPENDENCIES.txt'
    exclude 'META-INF/LICENSE.txt'
    exclude 'META-INF/NOTICE.txt'
    exclude 'META-INF/NOTICE'
    exclude 'META-INF/LICENSE'
    exclude 'META-INF/DEPENDENCIES'
    exclude 'META-INF/notice.txt'
    exclude 'META-INF/license.txt'
    exclude 'META-INF/dependencies.txt'
    exclude 'META-INF/LGPL2.1'
}

See for example: https://stackoverflow.com/questions/20827885/android-studio-0-4-duplicate-files-copied-in-apk-meta-inf-license-txt

According to the license of those libraries(Apache License 2.0 for instance), the license and notice files should be included.

My question: How can I add multiple files related to licensing(such as license.txt, notice.txt etc) from gradle into my project in order to be compliant with the licenses(technical detail: licences texts will be concatenated)?

There is a solution if you have only one license using the name license.txt (read: all license.txt copies are identical):

packagingOptions {
pickFirst  'META-INF/license.txt'
}

Otherwise, Google also released a Gradle plugin to manage dependencies licenses. See here. I didn't try it, but it looks like it's capable of aggregating every dependency, and even generating an activity displaying all of those licenses.

Add following into respective build.gradle file

packagingOptions {
        exclude 'META-INF/ASL2.0'
        exclude 'META-INF/LICENSE'
        exclude 'META-INF/NOTICE'
        exclude 'META-INF/NOTICE.txt'
        exclude 'META-INF/LICENSE.txt'
        exclude 'META-INF/MANIFEST.MF'
    }

I faced the same issue with my application. You need to make sure you have not added any libraries twice. If you have followed the firebase documentation https://firebase.google.com/docs/android/setup

Then you should not add firebase library inside android studio i.e. file->project structure->cloud->firebase

You have to do only one of the both, to use firebase in your android application.

At the end clean and rerun your app.

As an alternative to Marc Plano-Lesay's answer, you can also merge the files:

packagingOptions {
    merge "META-INF/license.txt"
}

Reference: Gradle API 4.2 Packaging Options

You can add multiple licence in gradle see this

I think you need to include only these options in build.gradle:

android {
    packagingOptions {
        exclude 'META-INF/DEPENDENCIES.txt'
        exclude 'META-INF/NOTICE'
        exclude 'META-INF/NOTICE.txt'
        exclude 'META-INF/LICENSE'
        exclude 'META-INF/LICENSE.txt'
    }
}

Surely it will work

packagingOptions {
 exclude 'META-INF/LICENSE.txt'
 exclude 'META-INF/NOTICE.txt'   }