gradle - Android Studio: Resolving Duplicate Classes

Question

When I try to run my android application on an Android device, the gradle console reports the following error:

Error:Execution failed for task ':app:transformClassesWithJarMergingForDebug'.
> com.android.build.api.transform.TransformException: java.util.zip.ZipException: duplicate entry: com/loopj/android/http/AsyncHttpClient$1.class

When I search for the "AsyncHttpClient" class, I see that it's indeed being found in two separate locations:

/Users/Afflatus/.gradle/caches/modules-2/files-2.1/com.loopj.android/android-async-http/1.4.9/5d171c3cd5343e5997f974561abed21442273fd1/android-async-http-1.4.9-sources.jar!/com/loopj/android/http/AsyncHttpClient.java

/Users/Afflatus/.ideaLibSources/android-async-http-1.4.9-sources.jar!/com/loopj/android/http/AsyncHttpClient.java

The first path seems to suggest it's a "cache" file... so I've tried invalidating & restarting my cache, but both files are still there after the gradle gets rebuilt and I try to run the application. I've read in alternate posts that it can be resolved by deleting one of the files... So I went to the cache location and deleted all the files found in the "1.4.9" folder... unfortunantly after reopening Android Studio, a new cache file gets created and I get the same error.

Other posts (here, here,here, and here) suggest if I add "./gradlew clean" to the root directory it would rebuild the gradle again just for the run (as far as I understand). So I tried doing that as well:

Which made my app's folder look like this:

But unfortunantly, that didn't help things I still get the same error. What am I doing wrong? What should I be doing?

Answer 1

Sometimes duplicate classes exception means that one of your dependencies uses implicitly the older or newer (with +) version of some library you also use in your project,

To resolve this issue you may add such block of code (put your library version after 'force') to your build.gradle file (Module:app):

configurations {
   all {
      resolutionStrategy {
          // do not upgrade above 3.12.0 to support API < 21 while server uses
          // COMPATIBLE_TLS, or okhttp3 is used in project
          force 'com.squareup.okhttp3:okhttp:3.12.0'
          force 'com.squareup.okhttp3:logging-interceptor:3.12.0'
      }
   }
}

You may also exclude some group from your dependencies. For a single dependency you way write:

dependencies {

    // example
    implementation('log4j:log4j:1.2.15') {
        exclude group: 'javax.jms', module: 'jms'
    }
}

Tested to work on Android Studio with Gradle Plugin version 3.4.2 and Gradle version 5.4.1. Credits go to Dimitar Dimitrov and Schalk Cronjé from gradle org discussion group