Here the answer, make Bundle as final
public void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.listview);
fillData();
boxAdapter = new ListAdapter(this, products);
ListView lvMain = (ListView) findViewById(R.id.lvMain);
lvMain.setAdapter(boxAdapter);
Button btn = (Button) findViewById(R.id.insert);
OnClickListener listener = new OnClickListener() {
@Override
public void onClick(View v) {
Dialog d = onCreateDialog(savedInstanceState);
d.show();
}
};
/** Setting the event listener for the add button */
btn.setOnClickListener(listener);
}