getBackground() return null

Question

So I'm trying to hook OnActivityResume using Xposed. This is one part of my code in after hook:

    ArrayList<View> views = new ArrayList<View>();
    listViews(views, rootView);
    Log.d("ViewListing", Integer.toString(views.size()));



    for(Iterator<View> i = views.iterator(); i.hasNext(); ) {

        final View item = i.next();
        Log.d("ViewListing", "View:" + item.getClass().getName() + ":" + Boolean.toString(item instanceof android.support.v7.widget.Toolbar));
        if(item.getClass().getName().equals("android.support.v7.widget.Toolbar")) {
            Log.d("ViewListing", "Found Toolbar!");
            Drawable d = (Drawable) XposedHelpers.getObjectField(item, "mBackground");
            Log.d("ViewListing", "And background?" + d);
        }
    }

The toolbar is found, but the drawable is null. (My goal is to get the background color)