Can i get the root view of activity where the user is currently

I mean not in the app but anywhere, suppose user open my app and then moved it whatsapp can I get the root view of that activity.

I tried this

private Bitmap takeScreenshot(){
        View rootView = findViewById(android.R.id.content).getRootView();
        rootView.setDrawingCacheEnabled(true);
        return rootView.getDrawingCache();
    }

but it return the view of activity where it is defined, is it possible to obtain other app root view?