In an Android ListActivity, I am adding a button as a footer in a ListView. How can I apply layout formatting to this button like centering it and/or width=fill_parent?

I have tried a few things such as using setLayoutParams(), but have not gotten it to work - the footer always disappears when I try anything.

Here is the basic code I am working with

closeButton = new Button(this);
closeButton.setText(getResources().getString(R.string.title_closeprocess));
closeButton.setOnClickListener(new OnClickListener(){
        public void onClick(View v) {               
            closeProcess();
        }

   });

getListView().addFooterView(closeButton);