Develop Reference

Multiple JComboBoxes with same data, every item choosable once

I'm growing desperate here ...:
I do have a FRAME with 40 JComboBoxes. At first, they offer all the same items.
If I choose on item in one specific ComboBox, it should be selected there and not be available in all the other 39 Boxes anymore.
I tried to use a ComboBoxModel for a long while, but now I think it doesnt make any sense: the Moment i remove the selected item from the model, it gets removed from the Box that it got selected in, too.
So does it make sense to do it like this:
Have 40 MyComboBoxes in the class GUI
Every MyComboBox implements an ItemListener
If an item is selected, the item gets removed from the other 39 lists;
if its deselected, it gets added to the other 39 lists
(but if I want to do it like that, the listener mustnt be an own class but the
itemEventChanged-method must be implemented anonymously in the GUI?!)
There's a better way, isnt it? Thanks a lot for your help!

for(int x =0;x<YourComboBoxArray.length();x++
{
if(e.getSource()==YourComboBoxArray[x])
{
try
{
ArrayList <String> OptionsList = new ArrayList();
for(int i=0;i<YourComboBoxArray[x].getItemCount();i++)
{
OptionsList.add(TeamPlayercmbx[x].getItemAt(i).toString();
}
DefaultComboBoxModel DCMB = new DefaultComboBoxModel(OptionsList.toArray());
YourComboBoxArray[x+1].setModel(DCMB);
YourComboBoxArray[x+1].removeItem(YourComboBoxArray[x].getSelectedItem());
}
catch(Exception ex)
{
//Log your errors or whatever you want to do if it's the last ComboBox in the Array
}
}
}
This assumes you have an action listener on each index of the Combo Box Array

JList - selecting option

how do i go do this, based on input in textfield, you get some results inside jlist, after you select option in jlist you then get an action, code examples would be appreciated... this is what i got so far:
final DefaultListModel<String> locations = new DefaultListModel<String>();
getTextFieldSearch().addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
for(int i=0;i<10;++i) {
locations.add(i, "blah");
}
}
});
JList<String> list_racentRaces = new JList<String>(locations);

Start by taking a look at How to Use Lists, which has lots of awesome code examples.
The basic idea would be to...
When your actionPerformed method is triggered, create a new DefaultListModel, assuming you don't have your own implementation, fill it with all the new items you need and apply it to the instance of list_racentRaces
If you want to maintain what was previously in the list, you should consider starting with a DefaultListModel and simply add the new items to it as you need to...
Then, attach a ListSelectionListener to list_racentRaces and when the valueChanged event is triggered, find the selected item(s) and do what ever you need to based on these result(s)
You can find more details and examples through How to Write a List Selection Listener

how to retrieve item ID from JList

I have a JList, where it displays names according to the DB. Associated with these names are IDs. for eg., foodId = 1, foodName = Chinese.
If i click on an item on the JList, i need to capture the foodID associated with the clicked foodName. i know a variable is needed.
when i have that value, I can pass that value into another method to retrieve the relevant food items associated with that foodId. Assume that getters & setters are done.
I have only the following, & am stuck. Please advise thank you.
list_1.addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent evt) {
//alter text of Label acc to clicked item # JList
JList list = (JList)evt.getSource();
System.out.println (list.getSelectedValue());
//store int value of item clicked # JList
int temp = 0;
temp = ???????????
//populate JPanel
Food food = new Food();
JPanel panel = new JPanel();
panel.setBounds(153, 74, 281, 269);
panel.add(food.populateWithButtons());
contentPane.add(panel);
}
});
list_1.setBorder(new LineBorder(new Color(0, 0, 0), 0));
//populate JList
list_1.setModel(food.populateJList());
public ListModel populateJList()
{
DefaultListModel model = new DefaultListModel();
ResultSet rs = null;
DataAccessObject db = new DataAccessObject();
db.setUp("customer");
String dbQuery = "SELECT store_Owner_Id, food_Category FROM store_owner";
rs = db.readRequest(dbQuery);
try
{
while (rs.next())
{
food_Category = rs.getString("food_Category");
store_Owner_Id = rs.getInt("store_Owner_Id");
model.addElement(food_Category);
System.out.println (store_Owner_Id); //test DB conn & print retrieved items
System.out.println (food_Category);
}
}
catch (Exception e)
{
e.printStackTrace();
}
db.terminate();
return model;
}

Suggestions:
Don't populate the JList with Strings but rather ...
If you populate your JList with objects that contain both the name and the ID, then you're doing well.
You will likely want to give your JList a cell renderer that helps it to show the information from the object that you want the JList to display.
Then getting the ID is simply a matter of getting the selected item from the JList inside whatever listener you're using, casting it to the object type that in fact is, and then calling the getter method, such as getId(), assuming that objects of this type have this method, and then use your ID.
Note though that this tells us nothing useful:
list_1.setModel(food.populateJList());
If my suggestions don't help you answer your question, then please provide more useful information and code, information that will help us to fully understand your problem.
Edit 2
Your latest code shows that you're doing what I recommended that you not do:
while (rs.next())
{
food_Category = rs.getString("food_Category");
store_Owner_Id = rs.getInt("store_Owner_Id");
model.addElement(food_Category); // ****** here
System.out.println (store_Owner_Id);
System.out.println (food_Category);
}
You're adding Strings to your DefaultListModel, and by doing this you lose all the other information that the database gave you.
Again do not add Strings to this model. Create a class that has two or more fields, one for the category String, and one for the owner ID, that has getters, setters, and a constructor that allows you to pass this information into objects of the class, create objects of this class in your while loop above, and add these to the JList model. Then give your JList a custom renderer which is better than giving the custom object a toString() method for this purpose.
Create a custom class, say called FoodInfo
Declare the DefaultListModel as one that accepts objects of this type, DefaultListModel<FoodInfo>
Then add objects of this type to the model:
e.g.,
DefaultListModel<FoodInfo> model = new DefaultListModel<FoodInfo>();
// ... other code to get database info
while (rs.next()) {
String foodCat = rs.getString("food_Category");
int id = rs.getInt("store_Owner_Id");
FoodInfo foodInfo = new FoodInfo(foodCat, id);
model.addElement(foodInfo);
}
Edit 3
As has been noted in comment by #dic19, don't use a MouseListener on the JList but rather use a ListSelectionListener as described in the JList Tutorial.

See Combo Box With Hidden Data. It will show you how to use a custom object without the need for a custom renderer. I know the title is "Combo Box" but the concept is identical for a JList.
When you use a custom renderer you break the default functionality of JList since you will no longer be able to select items using the keyboard. A properly designed GUI should allow the use to use the mouse or keyboard to select an item.

How to Check(Marked as checked) buttons in a program(or a checkbox) from just one Button?

Here is my question.Lets say that somebody made a checkbox in java and he is using it in a GUI interface so that the user can select a variety of options.Then the programmer wants to create a button inside the checkbox so that when the user checks that button all the other options will be checked as well.And when he unchecks that button of course all the other buttons will be unchecked.How is that possible in java?
Example :
o1 = new JCheckBox("Option 1");
o2 = new JCheckBox("Option 2");
o3 = new JCheckBox("Option 3");
All = new JCheckBox("All");
.....
CheckBoxHandler listener = new CheckBoxHandler();
All.addItemListener(listener);
......
Lets assume that the following code is on a class that was created as it implements ItemListener
public class CheckBoxHandler implements ItemListener
{
public void itemStateChanged(ItemEvent e)
{
if (e.getSource()==All)
if (e.getStateChange()==ItemEvent.SELECTED)
{
.... <------ (!!!)Here inside I am currently stack and I do not know how to
add the correct code in order to have all the other buttons checked.
}
}
}
Any help provided is really appreciated :)

Make use of the concept of array.
JCheckBox[] checkboxes = new JCheckBox[10];
When you need to apply some operation to all checkboxes, iterate over the array:
for( JCheckbox cb : checkboxes )
cb.doStuff();

You can call setSelected() on the JCheckbox (inherited from AbstractButton):
...
o1.setSelected(true); // or false
...
As #Juvanis mentions, instead of having three different references for o1, o2 and o3, you should use an array. Then, you can do something like
for( JCheckbox cb : checkboxes ) {
cb.setSelected(true);
}
to set all checkboxes in the array as checked.

CheckBoxes can have ActionListeners. Why not add an ActionListener to all the checkboxes that then checks if the one selected is checked or not and calls setSelected(true) or setSelected(false) on each one?
If you have a known small number of checkboxes (such as the 3 you talked about), you may just want to hard code it. However, if you need to make it modular or have a large number of check boxes, you can always store them in a data structure (as Juvanis said, an array would probably work nicely) and loop it

Java - Updating JList after changing an object

I have a JList which uses a DefaultListModel.
I then add values to the model which then appear in the JList. I have created a MouseListener which (when double clicked) allows the user to edit the current user number of that person they have selected.
I have checked that the actual object of that record is being changed, and it is. The only issue I'm having is getting the actual Jlist to update to show the new values of that object.
Snippets of the current code I have are:
Creating the JList and DefaultTableModel:
m = new DefaultListModel();
m.addListDataListener(this);
jl = new JList(m);
jl.addMouseListener(this);
Updating the object:
String sEditedNumber = JOptionPane.showInputDialog(this, "Edit number for " + name, number);
if (sEditedNumber != null) {
directory.update (name, sEditedNumber);
}
And (when jl is the JList and m is the DefaultTableModel):
public void contentsChanged(ListDataEvent arg0) {
jl.setModel(m);
}

Instead of setModel(), update your existing model using one of the DefaultListModel methods such as setElementAt(), which will fireContentsChanged() for you.

You need to call fireContentsChanged() on the ListModel.

You need to call DefaultListModel.fireContentsChanged(). But since this method is protected (I really wonder why), you can't do that directly. Instead, make a small subclass:
class MinoListModel<T> extends DefaultListModel<T>
{
public void update(int index)
{
fireContentsChanged(this, index, index);
}
}
Use it as your list model:
m = new MinoListModel<>();
jl = new JList(m);
After updating a user number, update the corresponding entry: m.update(theIndex);
Alternatively, if you don't want a subclass, you can just replace the JList element after the user number changed: m.setElementAt(theSameElement, theIndex);. Though this is somewhat cumbersome and having a subclass seems the cleaner approach.