Trying to programmatically set DPI for second screen on my Android device

Question

I have an Android device with 2 displays and I need to set the second display's DPI programmatically. It works with the following command over ADB (and then perform a restart to see the changes) :

wm density 160 -d 1

but when I try to programmatically run this command (and then restart the device):

 try {
        Runtime.getRuntime().exec("wm density "+Constants.DPI_TO_SET_DEVICE_TO+" -d 1");
    } catch (IOException e) {
        throw new RuntimeException(e);
    }

nothing seems to happen. Am I doing something wrong here? I've also researched using DisplayMetrics to do this programmatically as well, but that doesn't seem to be able to set a second display DPI that I'm aware of. Am I misunderstanding that?