Cross-platform code can not create, though I love the B4X application.
My complaint is:
Forum and not outside regular tutorial support.
Very simple stuff groove for days. But the solution is very easy. However, this solution does not have a support page we find a systematic way.
As for the problem. Perhaps others in need.
b4a.meta file in the project folder has occurred. This fix deleted by mistake. And I wasted my first week.
It's very difficult to reach a simple information ....