如何在JComboBox中填充数据? [英] How to populate data in a JComboBox?

问题描述

我创建了一个GUI并在外部放置了一个数据库，从中可以从中获取数据.我正在NetBeans中使用GUI构建器来执行此操作.有谁知道用来自数据库的值填充jComboBox的简单方法吗?当我运行项目时，没有错误，但是组合框保持为空.

I have created a GUI and have a database located externally in which I fetch data from. I am using the GUI builder in NetBeans to do this. Does anyone know of a simple way to populate a jComboBox with values coming from the database? When I run the project there are no errors but the combo box remains empty.

以下是设置带有折扣名称的组合框的代码:

Here is the code that sets the combo box with the names of discounts:

public void setDiscountNames(String type, JComboBox cbox) {        
    cbox.removeAllItems();     
    ArrayList<Discount> names = new ArrayList<Discount>();
    try {        
        Connection con = null;
        PreparedStatement stmt = null;
        ResultSet rs = null;            
        con = DriverManager.getConnection("jdbc:mysql://localhost:3306/abpp034?user=abpp034&password=120001772");
        stmt = con.prepareStatement("SELECT Name FROM Discount WHERE Type = \"" + type + "\"");
        rs = stmt.executeQuery();

     while(rs.next()){                     
         cbox.addItem(rs.getString("Name")); 
        }
    } catch (SQLException ex) {
        Logger.getLogger(Model.class.getName()).log(Level.SEVERE, null, ex);
    } 
}

这与jComboBox对象位于不同的类中.此类称为模型.

This is located in a seperate class from the jComboBox object. This class is called Model.

在这里我以一种名为DiscountGUIView的形式调用setDiscountNames方法:

Here is the place I call the setDiscountNames method in a form called DiscountGUIView:

private void jComboBox1ActionPerformed(java.awt.event.ActionEvent evt){                                           
     model.setDiscountNames("Fixed", jComboBox1);
}                                          

好的(更新)查询确实会打印结果:

Okay (Update) the query does print the results:

run:

旅行标准 固定标准 建立成功(总时间:1秒)

Travel Standard Fixed Standard BUILD SUCCESSFUL (total time: 1 second)

推荐答案

这是您的基本错误.

classConstructor(){
setDiscountNames("Fixed", jComboBox1); // call this method here.. This will work.

}

如果这些值正确打印，请尝试此操作.

If the values are printing correctly then try this..

List<String> strings = new ArrayList<String>();
while(rs.next()){

     strings.add(rs.getString("Name"));  // Confirm if "Name" is valid


    }
cbox.addItem(strings);

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