FAQ #10906, published on 2015-06-18, updated on 2016-05-23
How to fix an Android compile error : "INSTALL_FAILED_DEXOPT" or "Too many method reference" or an install error -11 ?
Basically all these errors mean the same thing : the App contains too many elements for the compiler, so the first action is to make sure that there is no unused element in your Android configuration (windows, procedures, etc). 

In version 20, simply check the "Reduce the size of generated code" option on the Configuration plane of the APK generation Wizard.

In version 21, two options are available : first check "Enable the multidex generation", then if needed the "Reduce the size of generated code" option.