based on this link , the correct answer (which i've tested myself) is:
put this code in the constructor or the onCreate() method of the dialog:
getWindow().setLayout(WindowManager.LayoutParams.MATCH_PARENT,
WindowManager.LayoutParams.MATCH_PARENT);
in addition , set the style of the dialog to :
<style name="full_screen_dialog">
<item name="android:windowFrame">@null</item>
<item name="android:windowIsFloating">true</item>
<item name="android:windowContentOverlay">@null</item>
<item name="android:windowAnimationStyle">@android:style/Animation.Dialog</item>
<item name="android:windowSoftInputMode">stateUnspecified|adjustPan</item>
</style>
this could be achieved via the constructor , for example :
public FullScreenDialog(Context context)
{
super(context, R.style.full_screen_dialog);
...
EDIT: an alternative to all of the above would be to set the style to android.R.style.ThemeOverlay and that's it.