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 value?
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.
来源：https://stackoverflow.com/questions/7594527/how-to-obtain-the-exact-dpi-value-of-android-device