code: public DrawerBuilder withActivity(@NonNull Activity activity) {
          this.mRootView = (ViewGroup) activity.findViewById(android.R.id.content);
          this.mActivity = activity;
          this.mLayoutManager = new LinearLayoutManager(mActivity);
          return this;
      }
docs: Sets the activity which will be generated for the generation
  The activity is required and will be used to inflate the content in.
  After generation it is set to null to prevent a memory leak.
  
  @param activity current activity which will contain the drawer