Execution failed for task: ':app:preDexDebug'
问题 I am experiencing that famous ':app:preDexDebug'-error. First of all: Cleaning the project or rebuilding it works without errors. Under default settings I set the project bytecode version to 1.7 and under SDK Location in the project structure the JDK location seems to be correct, too. After a while of researching I still did not find the solution for this problem. The error occurs when I try to run the project under Android Studio. Like mentioned before, cleaning, rebuilding and syncing with