java - JComboBox 中的 MySQL 表值

Question

我设计了一个带有MySQL表的swing界面。我以某种方式放置两个组合框，当选择第一个组合框值(品牌名称)时，第二个组合框值(所选品牌下的可用项目)将通过 mysql 查询加载。我的代码是...

try{
    String url = "jdbc:mysql://localhost:3306/databasename";
    String login = "root"; String password = ""; Connection con = DriverManager.getConnection(url, login, password);
    try{
        comboBox1 = new JComboBox(); comboBox1.setEditable(false);
        comboBox1.addItem("- - -");
        Statement stmt1=null;
        String query1 = "SELECT brand FROM brands";
        stmt1 = con.createStatement();
        ResultSet rs1 = stmt1.executeQuery(query1);
        while(rs1.next()) {comboBox1.addItem(rs1.getString(1));}
        comboBox2 = new JComboBox(); comboBox2.setEditable(false);
        comboBox1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event){
                String comboBox1Selected=comboBox1.getSelectedItem().toString();
                try{
                    Statement stmt2=null;
                    String query2 = "SELECT item FROM "+comboBox1Selected+"";
                    stmt2 = con.createStatement();
                    ResultSet rs2 = stmt2.executeQuery(query2);
                    while(rs2.next()) {comboBox2.addItem(rs2.getString(1));}
                }
                catch (SQLException ex1) {JOptionPane.showMessageDialog(null,"Failed to Item-List..!"); ex1.printStackTrace(); return;}
            }
         });
    }
    catch (SQLException ex2) {JOptionPane.showMessageDialog(null,"Failed to Brand-List..!"); ex2.printStackTrace(); return;}
}
catch (SQLException ex3) {ex3.printStackTrace(); JOptionPane.showMessageDialog(null,"Unable to Connect..!"); return;}

问题是，即使组合框正常工作，如果我从第一个组合框中选择另一个选项，第二个组合框不会避免“旧值”(它们与新值一起出现)。

可能是什么原因..？任何人都可以解释一下..？ 提前致谢。

Answer 1

在此处添加新项目之前调用 comboBox2.removeAllItems() while(rs2.next()) {comboBox2.addItem(rs2.getString(1));}