Android Question MaterialDialogExample compile error

Hi,
I tried to run MaterialDialogExample on a Nexus 7 2013 but got this error...
Any suggestion?
Thanks in advance

Generating R file. (2.62s)
Compiling debugger engine code. (2.14s)
Compiling generated Java code. Error
src\de\amberhome\materialdialogs\example\main.java:17: error: cannot access RecyclerView
public class main extends de.amberhome.materialdialogs.MaterialDialogsActivity implements B4AActivity{
^
class file for android.support.v7.widget.RecyclerView not found
1 error

javac 11.0.1