Android :: Invoking A Context Menu When An OnClickListener Is Applied To An Activity

Please find the code sample below:

public class Abc extends Activity implements OnClickListener{
private ListView displayList;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mainlayout);
displayList =(ListView)findViewById(R.id.addressbooklistview);
addressbookAdapter = new CustomListAdapter(this,addressbookList);
displayList.setAdapter(addressbookAdapter);
registerForContextMenu(displayList);}
I am not able to invoke the context menu on long press. Please let me know any solution for the same.