JComboBox has items, but drop down list blank ?

OK, good suggestion, here we go :

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import java.awt.*;

import javax.swing.*;

import java.awt.event.*;

import java.util.*;

public class Java_Test extends JPanel

{

static JTabbedPane Tabbed_Pane=new JTabbedPane();

JComboBox Contacts_ComboBox;

Customer_Info_Panel Customer_Info_Panel=new Customer_Info_Panel();

Java_Test()

{

JPanel A_Tab_Panel=new JPanel();

A_Tab_Panel.setPreferredSize(new Dimension(300,200));

A_Tab_Panel.add(Customer_Info_Panel);

JPanel B_Tab_Panel=new JPanel();

B_Tab_Panel.setPreferredSize(new Dimension(300,200));

Contacts_ComboBox=new JComboBox(Customer_Info_Panel.Contacts_Id_Vector);

Contacts_ComboBox.setMaximumRowCount(30);

Contacts_ComboBox.setSelectedIndex(-1);

Contacts_ComboBox.setPreferredSize(new Dimension(129,22));

B_Tab_Panel.add(new JLabel("Select Customer Info From List :"));

B_Tab_Panel.add(Contacts_ComboBox);

Tabbed_Pane.addTab("A : Enter Customer Info",null,A_Tab_Panel,null);

Tabbed_Pane.addTab("B : Use entered info",null,B_Tab_Panel,null);

add(Tabbed_Pane);

setPreferredSize(new Dimension(500,300));

}

public static void main(String[] args)

{

final Java_Test demo=new Java_Test();

Dimension Screen_Size=Toolkit.getDefaultToolkit().getScreenSize();

final JFrame frame=new JFrame("JUninstaller");

frame.add(demo);

frame.addWindowListener(new WindowAdapter()

{

public void windowActivated(WindowEvent e) { }

public void windowClosed(WindowEvent e) { }

public void windowClosing(WindowEvent e) { System.exit(0); }

public void windowDeactivated(WindowEvent e) { }

public void windowDeiconified(WindowEvent e) { demo.repaint(); }

public void windowGainedFocus(WindowEvent e) { demo.repaint(); }

public void windowIconified(WindowEvent e) { }

public void windowLostFocus(WindowEvent e) { }

public void windowOpening(WindowEvent e) { demo.repaint(); }

public void windowOpened(WindowEvent e) { }

public void windowResized(WindowEvent e) { demo.repaint(); }

public void windowStateChanged(WindowEvent e) { demo.repaint(); }

});

frame.pack();

frame.setBounds((Screen_Size.width-demo.getWidth())/2,(Screen_Size.height-demo.getHeight())/2-10,demo.getWidth(),demo.getHeight()+38);

frame.setVisible(true);

}

}

class Customer_Info_Panel extends JPanel

{

Vector<String> Contacts_Id_Vector=new Vector<String>();

JComboBox Contacts_Id_ComboBox=new JComboBox(Contacts_Id_Vector);

Customer_Info_Panel()

{

Contacts_Id_ComboBox=new JComboBox(Contacts_Id_Vector);

Contacts_Id_ComboBox.setMaximumRowCount(30);

Contacts_Id_ComboBox.setSelectedIndex(-1);

Contacts_Id_ComboBox.setEditable(true);

Contacts_Id_ComboBox.setPreferredSize(new Dimension(129,22));

Contacts_Id_ComboBox.addActionListener(new ActionListener()

{

public void actionPerformed(ActionEvent evt)

{

String New_Item=Contacts_Id_ComboBox.getSelectedItem()==null?"":Contacts_Id_ComboBox.getSelectedItem().toString().trim();

if (!Contacts_Id_Vector.contains(New_Item)) Contacts_Id_Vector.add(New_Item);

}

});

add(new JLabel("Please Enter Customer Info Below :"));

add(Contacts_Id_ComboBox);

setPreferredSize(new Dimension(270,170));

}

}

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Run the program, do the following :

1. In Tab A, enter "abc", hit Enter key, then goto Tab B and see it ? It's there.

2. In Tab A again, enter "xyz", hit enter key, goto Tab B, now drop down the list, nothing is there, but you know there are two items in the list. Just click on the blank list, an item will show up, if you look at the drop down list now, you can see both "abc" and "xyz".

3. In Tab A again, enter "123", hit enter, and goto Tab B, drop down the list, what you see ? Nothing ! Click on the last position on the blank list, you will get "123", and now if you drop down the list again, you will see all 3 items !

Am I doing something wrong ?

Frank

Ni_Mina at 2007-7-15 3:43:46 >

Thanks for your advice, good point.

The reason I designed it this way is because I want to share the Contacts_Id_Vector inside class Customer_Info_Panel with other parts of the program, the idea is that Contacts_Id_Vector is the commom (shared) data structure, it is entered/modified inside the Contacts_Id_ComboBox of Customer_Info_Panel, while the latest information of Contacts_Id_Vector can be accessed from another combobox in another tab, in this case it's Contacts_ComboBox. Since those two comboboxes share the same Contacts_Id_Vector, I expect the latest information to show up in both of them after one of them is updated. Maybe there is a way to repaint the dropdown list that I need to do somewhere that I'm missing now, it seems both comboboxes contains the correct items in the dropdown list, but just not painting them correctly. Once user clicks on the empty list, it'll repaint itself and display the right content.

So the question is how to programmatically update the UI after changing the combobox ?

Frank

Ni_Mina at 2007-7-15 3:43:46 >

> When a component is selected in one, its selected in all. This seems to be a bug in the MVC design of the JComboBox."

I would agree. All other components have a separate SelectionModel. The Model should only store data not the selection.

However, I'm not sure what your requirement is. So I suggest you post a new Thread stating your requirements. It sound like you need the ability to add and remove items from the combo box and you want the changes to propagate to all combo boxes. What happens if you remove an item from one combo box that is currently selected in another combo box?

camickra at 2007-7-15 3:43:46 >

> In that case I guess it should automatically update

> all the comboBoxes that share this vector and

> listeners for all those comboBoxes be notified.

>

For the simple example illustrated, did you try the following:

Contacts_ComboBox=new JComboBox(Customer_Info_Panel.Contacts_Id_ComboBox.getModel());

Since the Vector is enclosed in ComboBoxModel and the model is shared between the two JComboBoxes, the Vector is shared and it will do what you want in terms of automatic updating. However, because the selection is also shared, the two JComboBoxes will select the same item in the Vector. If this is not desirable, then I think what you may have to do is duplicate the Vector. When the Vector in Customer_Info_Panel is changed, change the one in Contacts_ComboBox., through the model. Its ugly, but I have not found a way to work around the blank pull down list. I have set a break point in the update process and looked at the objects contained in the JComboBox and could not find one that obviously was out of synchronization. A Vector seems to be too low of a level for being shared between the two UIs and one of the intermediate objects appears to be maintaining some memory of how many elements are in the Vector. Because Swing was intending that sharing be done at the model level, it should not be surprising that sharing at a lower level does not work exactly right. In fact, it is surprising that it works as well as it does.

kb0oysa at 2007-7-15 3:43:46 >