How to obtain the exact dpi value of android device?

we can use DisplayMetrics.densityDpi to obtain a approximate dpi value of the device,but i eager to know how to obtain the exact dpi val开发者_StackOverflowue?

Use DisplayMatrics.xdpi and DisplayMatrics.ydpi

xdpi    The exact physical pixels per inch of the screen in the X dimension.
ydpi    The exact physical pixels per inch of the screen in the Y dimension.

getResources().getDisplayMetrics().xdpi
getResources().getDisplayMetrics().ydpi

I think you can accesss this through the class DisplayMetrics and the field densityDpi.