没有特定错误，MySQL连接在Android中不起作用

Question

当我尝试连接到MySQL数据库时遇到此问题。它告诉我这是错误的，我不知道为什么，因为它没有给我特定的错误。

这只是让我知道我在渔获物中所写的内容。 顺便说一句，我正在使用MySQL Connector / J版本5.1.47。

这是连接代码：

    private class GetData extends AsyncTask<String,String,String> {
    String msg = "";
    //JDBC driver name and database URL
    static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
    static final String DB_URL = "jdbc:mysql://" +
            DbStrings.DATABASE_URL + "/" +
            DbStrings.DATABASE_NAME;

    @Override
    protected void onPreExecute() {
        ProgressTextView.setText("Connecting to Database...");
    }
    @Override
    protected String doInBackground(String... params) {
        Connection conn = null;
        Statement stmt = null;

        try {
            Class.forName(JDBC_DRIVER);
            conn = DriverManager.getConnection(DB_URL, DbStrings.USERNAME, DbStrings.PASSWORD);

            stmt = conn.createStatement();
            String sql = "SELECT * FROM zimmerstamm";
            ResultSet rs = stmt.executeQuery(sql);

            while (rs.next()) {
                String Bemerkung = rs.getString("Bemerkung");
                Double Zimmer = rs.getDouble("Zimmer");

                fruitsMap.put(Bemerkung, Zimmer);
            }
            msg = "Process complete";

            rs.close();
            stmt.close();
            conn.close();
        } catch (SQLException connError) {
            msg = "An exception was thrwon for JDBC.";
            connError.printStackTrace();
        } catch (ClassNotFoundException e) {
            msg = "And exception was No class found.";
            e.printStackTrace();
        }