使用表值填充组合框

Question

EDIT(NEW):

Still haven't figured out how to populate the cboxCustomers . I've been at it for the past day or two, but without luck.

In case anyone can help: http://pastebin.com/e5wibRYw

I went from cats to customers , btw.

I tried Mr. Xymon's approach, but didn't implement it correctly since it didn't work.

Whatever event I used to handle the population I always got NullPointerException for whatever control/event I was trying to use.

OLD:

There's a JForm . On it, there's a single combo box. Also have a single table with cats - cats . Each cat has id , and catName .

What I wanted to do was when I click on the combo box, thus expanding it, populate it with all id of cats that are found in cats table.

SLOVED. Asnwer below. Unfortunately I receive numerous unreported exception java.sql.SQLException from the lines I've indicated with > :

private void cboxCatsMouseClicked(java.awt.event.MouseEvent evt) {
        // TODO add your handling code here:
        // create an array list to be filled with cat's ids
        ArrayList<String> cats = new ArrayList<String>();
        String query = "SELECT id FROM cats ORDER BY id";
        >java.sql.PreparedStatement stm = connection.prepareStatement(query);

        >ResultSet rs = stm.executeQuery(query);

        >while(rs.next()){
            >String cat = rs.getString("id");
            // add cat's ids tp the array list
            cats.add(cat);
        }

        >rs.close();

        // populate the combo box
        DefaultComboBoxModel model = new DefaultComboBoxModel(cats.toArray());
        cboxCats.setModel(model);
    }

OLD ANSWER:

I think I fixed it. I just had to wrap all of the highlighted lines of code together into one big try-catch statement that would catch SQLException . Problem is - the combo box doesn't get populated with id values when I expand it. Why is that? Am I using the wrong event?

Answer 1

Isn't better to populate your combo box with cat's name instead of the id? I came up with a different solution by directly adding field value into model instead of using ArrayList. You have to perform it within the constructor to populate the combo box upon loading the form.

DefaultComboBoxModel list = new DefaultComboBoxModel();
JComboBox cbo_cats = new JComboBox(list);


// at constructor or a user-defined method that's called from constructor
   try{     
      // assume that all objects were all properly defined
      s = con.createStatement();
      s.executeQuery("SELECT * FROM cats ORDER BY catName");
      rs = s.getResultSet();
      while(rs.next()){
         //int id = rs.getInt("id");
         //list.addElement(id);

         String c = rs.getString("catName");
         list.addElement(c);
      }
   }catch(Exception err){
      System.out.println(err);
   }

As you can see I didn't use prepared statements but you can easily change that.