ApplicationWindow set the screen size ?

I trying set the screen size using ApplicationWindow for learning events.When I was running on desktop work well.But when I was running on android ,I encountered trouble problem. When I kept the phone upright and start application, the form fits to screen well. than I tilt the phone and I was seing that the half of screen wrap white color . How can I overcome from this problem. I set the widht and height like that ApplicationWindow{     id:a     width:Screen.width     height:Screen.height     color:"#eee8e8"}