RDC problem

i'm a b4a beginners and i'm trying to make an android application that connect to mysql database.
when i compile/debug, i got this error :

B4A version: 6.00
Parsing code. (0.01s)
Compiling code. (0.29s)
Compiling layouts code. (0.01s)
Organizing libraries. (0.00s)
Generating R file. (3.29s)
Compiling debugger engine code. (3.93s)
Compiling generated Java code. (3.92s)
Convert byte code - optimized dex. Error
UNEXPECTED TOP-LEVEL EXCEPTION:
java.lang.IllegalArgumentException: already added:...

RDC problem

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