How to get the Android device screen size from the adb command line?

You can also access the WindowManager through ADB:

$ adb shell wm
usage: wm [subcommand] [options]
       wm size [reset|WxH]
       wm density [reset|DENSITY]
       wm overscan [reset|LEFT,TOP,RIGHT,BOTTOM]

To get the screen resolution:

$ adb shell wm size
Physical size: 2880x1600

To get the screen the density:

$ adb shell wm density
Physical density: 320

You can also override the density by adding the new density:

$ adb shell wm density 160