White screen when running ketai code

import ketai.sensors.*;
KetaiSensor sensor;
sensor = new KetaiSensor(this);

Hello. I think this is a very simple code, but it still does not work. Phone (Android 5.1.) is recognized and app is opened, but as a white screen.
I think it is a problem of permissions or something else related with ketai. I have a more complex code, without errors, that does not run.

with this code it s difficult to guess what is supposed to be displayed on screen!