public ViewGroup getActionBar(View view) {    try {        if (view instanceof ViewGroup) {            ViewGroup viewGroup = (ViewGroup) view;            if (viewGroup instanceof android.support.v7.widget.Toolbar) {                return viewGroup;            }            for (int i = 0; i < viewGroup.getChildCount(); i++) {                ViewGroup actionBar = getActionBar(viewGroup.getChildAt(i));                if (actionBar != null) {                    return actionBar;                }            }        }    } catch (Exception e) {    }    return null;}

ViewGroup actionBar = getActionBar(getWindow().getDecorView());actionBar.setBackgroundResource(R.color.colorAccent);

获得根视图

decorView = (ViewGroup) getWindow().getDecorView().findViewById(android.R.id.content);