public class DisplayCustomersActivity 
    extends Activity implements Button.OnClickListener
{
    private SalesDB sdb;
    private ListView lvDCList;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.displaycustomers);
        lvDCList = (ListView) findViewById(R.id.lvDCList);
        sdb = new SalesDB(this);
        SQLiteDatabase db = sdb.getReadableDatabase();
        Cursor results = db.query(sdb.TABLE_CUSTOMER, new String[] {sdb.CUSTOMER_ID, sdb.CUSTOMER_NAME, sdb.CUSTOMER_GENDER}, null, null, null, null, null);
        int resultCount = results.getCount();
        String[] customers = new String[resultCount];
        if (resultCount == 0 || !results.moveToFirst()) {
            customers = null;
        } else {
            for(int i=0; i<resultCount; i++) {
            //Process results to String array here
            ...
            ...
            results.moveToNext();
        }
    }
}