Thank you Erel! I loaded an opaque hiding panel on top of the "older" views. This successfully covered all theses "lower" views (labels, text, camera panel), but not the buttons. As there were only five buttons, I just disabled the buttons et voila, the Tabhost appeared undisturbed and I added a back button. On leaving this "upper" layer with the back button, I removed the hiding panel, the Tabhost and the back button and the original views become visible and active again.
I am sure the B4XDialog will provide a more elegant solution. I will try it eventually.