I think I found it
In the Designer, I put an ImageView and define the Image there in the Designer
Actualy I ddon't need the ImageView , so I set Visible to False and there ImageView is not used in the Code,
I don't delete it, because I guess I need it in the future.
These was the Reason for the Exception , I delete the ImageView and it works.
Don't know why, but in the project-dir on the Phone, b4a creats a folder named "virtual_assets" and here I find all the used bmp-files.
On a newer Android these folder dosn't exists.