DisplayMetrics returning all zero

I am trying to access some DisplayMetrics data and everything is returning zero. This is how I am initializing开发者_如何学C display metrics object:

DisplayMetrics display = new DisplayMetrics();

and when I call display.heightPixels it's just zero. Do I need a permission or something to access DisplayMetrics?

This is not how to use DisplayMetrics.

This is how:

final WindowManager w = (WindowManager) context
            .getSystemService(Context.WINDOW_SERVICE);
final Display d = w.getDefaultDisplay();
final DisplayMetrics m = new DisplayMetrics();
d.getMetrics(m);

// m now contains reliable data

I think you have to use getWindowManager().getDefaultDisplay().getMetrics(metrics);, before call the method display.heightPixels

You should call: getWindowManager().getDefaultDisplay().getMetrics(display);

before calling display.heightPixels