Draw an inch square on Android

I'd like to set up a program that draws an inch square regardless of the terminal.
I thought about
①Get 1 dpi and get 1 inch square px

 int dpi=getResources().getDisplayMetrics().densityDpi;

仮にIf it is 100px, it will be 10x10, so do をpx.

intippenn=(int)Math.sqrt(dpi);

正方Specify xpx on one side of the square

rect.set(0,0,ippenn,ippenn);

It was written in this way, but it didn't work at all and the square itself didn't appear.
If you rewrite the variable ippenn to 100 and so on ( rect.set(0,0,100,100);), the square was displayed, so I think drawing the square itself is correct.
How can I make it?