Java
Java

adding new items into JComboBox

Hi,

I have a JComboBox already. And now I would like make this JComboBox bigger, more choices, if some flags are set. How can I do this?

Here is my codes...
String ComboBoxStr[] = { "a1", "a2", "a3", "a4", "a5"};
JComboBox aComboBox = new JComboBox(ComboBoxStr);
Boolean setFlag = false;

if (setFlag == true)
{
// let say if I want to have 5 more choices like this...ComboBoxStr[] = { "a1", "a2", "a3", "a4", "a5", "a6", "a7", "a8", "a9", "a10"};

// so what can I do here???
}

xenia27Asked: 2004-04-29

Who is Participating?

LVL 37

zzynxSoftware engineerCommented: 2004-04-30

Avoiding duplicates:

Set theSet = new HashSet()

1) Adding to the combo box should be like this:

instead of

      yourCombo.add("a1");

you should write:

      if ( !theSet.contains("a1") ) {
       yourCombo.add("a1");
       theSet.add("a1")
      }

2) Removing
instead of

      yourCombo.removeItem("a1");

you should write:

      yourCombo.removeItem("a1");
      theSet.remove("a1");

LVL 92

objectsCommented: 2004-04-29

aComboBox.addItem(newitem);

xenia27Author Commented: 2004-04-29

should I have a new String array for "newitem"?? Or just simply put a string??

LVL 92

objectsCommented: 2004-04-29

you can just add the new items. eg.
aComboBox.addItem("a6");
aComboBox.addItem("a7");
aComboBox.addItem("a8");
aComboBox.addItem("a9");
aComboBox.addItem("a10");

LVL 92

objectsCommented: 2004-04-29

or you could use a loop if you already have an array

xenia27Author Commented: 2004-04-29

If I do have an ActionListener when I first initialized aComboBox and now I add some new items...will the new items also ahve action listener???

LVL 92

objectsCommented: 2004-04-29

yes

xenia27Author Commented: 2004-04-29

so that means I don't need to add ActionListener to the new items?? Ok...so if I want to remove the new item...I need to use "removeItem"??

How can I know whether the new item I wanna add is existing in a JComboBox so I won't add another one again??

LVL 37

zzynxSoftware engineerCommented: 2004-04-30

>> so that means I don't need to add ActionListener to the new items??
The actionlistener listens to actions happening on *the combobox* no matter how many items are in it

>> if I want to remove the new item
To remove you can use
void removeItem(Object anObject)
or
void removeItemAt(int anIndex)

For the first you have to pass the object that is in it
For the first you only need to pass the index

>>How can I know whether the new item I wanna add is existing in a JComboBox so I won't add another one again??
Whenever you add an item to it or remove an item from it, you could also add/remove it from a Set.
Then before adding you could look if it exists in the set. If so, you shouldn't add it anymore.
(The Set is for not having to interrogate each item of the Combobox to check if the item you want to insert is already in)