Object reference not set to an instance of an object

I have an custonAdapter that creates a view with a clickable button insdie of it ... so when i click on the button i run a public function of the activity class that my list and views will be

So in my main activity that contains this list i have this function

public void refazLista(){

    vinhoEnumerable = pegaVinhos.getVinhos();

        vinhoList = vinhoEnumerable.ToList ();

    lista.Adapter = new adapterVinho(this,vinhoList);

}

and inside my button.Click i do this

pegaMain.refazLista();

but it gives me that code im stuck any hints ?