java - statements.executeQuery() 不起作用

Question

statement = conRecieved.createStatement();
resultSet = statement.executeQuery("Select * from actor");

在这个if中我检查它是否返回任何结果，但它不输入这个if

if (resultSet.next()) {
   Toast.makeText (getActivity (), "ResultsetWorks", Toast.LENGTH_SHORT) .show ();
} else {
   Toast.makeText (getActivity (), "REsult set no results", Toast.LENGTH_SHORT) .show ();
}

连接数据库的过程是在一个AsynTask类中执行的，它给我连接，创建的Connection对象，错在哪里？我尝试强制转换收到的连接，但不起作用。

AsyncTaskConexion asyncTaskConexion = new AsyncTaskConexion(getActivity(), new GetConnection() {
    @Override
    public void getConnection(Connection conexion) {
        if(conexion!=null){
            Connection conRecieved = (Connection )conexion;

Answer 1

I fixed it by running the query in a separate thread, not using the mainthread. I do not know if this is the best solution but it works.

AsyncTaskConexion asyncTaskConexion = new AsyncTaskConexion(getActivity(), new GetConnection() {
        @Override
        public void getConnection(Connection conexion) {
            if(conexion!=null){
                Connection conexionRecibida = conexion;
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try {                             
                            Statement statement = conexionRecibida.createStatement();
                            ResultSet resultSet = statement.executeQuery("Select * from actor");

with the method runOnUiThread(... you can iteract with the Ui elements

                            getActivity().runOnUiThread(new Runnable() {
                                public void run() {
                                    try {
                                        if(resultSet.next()){
                                            Toast.makeText(getActivity(),"ResultsetWorks", Toast.LENGTH_SHORT).show();
                                        }else{
                                            Toast.makeText(getActivity(),"Empty ResultSet", Toast.LENGTH_SHORT).show();
                                        }
                                    } catch (SQLException e) {
                                        e.printStackTrace();
                                    }
                                }
                            });