How to get the Display Size in Inches in Android?

Question

I need for my Application the exact inch of a display. My current solution is:

double inch;
double x = Math.pow(widthPix/dm.xdpi,2);
double y = Math.pow(heigthPix/dm.ydpi,2);
double screenInches = Math.sqrt(x+y);

inch = screenInches;

inch = inch * 10;
inch = Math.round(inch);
inch = inch / 10;

Is there a better way to get the display inch? Current on my test device 4 inch it say 5.9 and that is wrong...

Answer 1

The following gave me a a result quite close to the specs:

    DisplayMetrics dm = getResources().getDisplayMetrics();

    double density = dm.density * 160;
    double x = Math.pow(dm.widthPixels / density, 2);
    double y = Math.pow(dm.heightPixels / density, 2);
    double screenInches = Math.sqrt(x + y);
    log.info("inches: {}", screenInches);

Output: inches: 4.589389937671455
Specs: Samsung Galaxy Nexus (720 x 1280 px, ~320 dpi, 4.65")

Please note, that dm.heightPixels (or dm.widthPixels depending on your orientatation) does not necessarily provide accurate information, since soft keys (as used in the Galaxy Nexus) are not added to the height (or width).

Answer 2

Try this.... This will give you the exact size of the display..

static String getDisplaySize(Activity activity) {
    double x = 0, y = 0;
    int mWidthPixels, mHeightPixels;
    try {
        WindowManager windowManager = activity.getWindowManager();
        Display display = windowManager.getDefaultDisplay();
        DisplayMetrics displayMetrics = new DisplayMetrics();
        display.getMetrics(displayMetrics);
        Point realSize = new Point();
        Display.class.getMethod("getRealSize", Point.class).invoke(display, realSize);
        mWidthPixels = realSize.x;
        mHeightPixels = realSize.y;
        DisplayMetrics dm = new DisplayMetrics();
        activity.getWindowManager().getDefaultDisplay().getMetrics(dm);
        x = Math.pow(mWidthPixels / dm.xdpi, 2);
        y = Math.pow(mHeightPixels / dm.ydpi, 2);

    } catch (Exception ex) {
        ex.printStackTrace();
    }
    return String.format(Locale.US, "%.2f", Math.sqrt(x + y));
}