update 3.1 from 3.0 compile ERROR Multiple dex files define

[snow__fly]

update 3.1 from 3.0 later，ERROR in android 5.0 before:

Error:Error converting bytecode to dex:
Cause: com.android.dex.DexException: Multiple dex files define Lorg/webrtc/VideoCapturerAndroid$CameraErrorHandler;

:app:transformClassesWithDexForDebug FAILED

Error:Execution failed for task ':app:transformClassesWithDexForDebug'.
> com.android.build.api.transform.TransformException: com.android.ide.common.process.ProcessException: java.util.concurrent.ExecutionException: com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: Process 'command 'D:\Program Files\Java\jdk1.8.0_60\bin\java.exe'' finished with non-zero exit value 2

Information:BUILD FAILED

But android 5.0 later no error.，run OK。

[Chunbo_H_Intel1]

Hi Snow,

We've never met this issue...

Please try to clean the environment and rebuild.

Thanks!

[Modi__Vivek]

I got the same error below API level 21.