code: public void setTypeface(Activity activity, String typefaceName, int style) {
  		setTypeface((ViewGroup) activity.getWindow().getDecorView(), typefaceName, style);
  	}
docs: Set the typeface to the all text views belong to the activity.
  Note that we use decor view of the activity so that the typeface will also be applied to action bar.
  @param activity the activity.
  @param typefaceName typeface name.
  @param style the typeface style.