assign keys for combo box in java

Question

I want to add a JComboBox in Swing that is simple but I want to assign the values for each items in combo. I have the following code

    JComboBox jc1= new JComboBox();
    jc1.addItem("a");
    jc1.addItem("b");
    jc1.addItem("c");

Now what I want is that when click on combo box it should return 1, 2 and 3 correspondingly instead of a ,b, c. Is there any way to assign the key values for each items in combo box?

Answer 1

You can add an item as an object instead of adding String like this:

JComboBox<ItemClass> jc = new JComboBox<ItemClass>();
    jc.addItem(item1);
    jc.addItem(item2);
    jc.addItem(item3);

So to return key, the function of the event is : jc.getSelectedItem().getKey Doing this way you have to override the toString() function of class ItemClass to return the string you want to show in combobox.

Btw, for return number, you may try : jc.getSelectedIndex(), it'll return your index of your string (0 1 2 for "a" "b" "c")

Answer 2

you can create your own Model and add it to the combo box instead of adding Strings directly.

check Java ComboBoxModel.

you can find more info in this thread

Answer 3

Wrap your data in a simple class:

class MyData {
  int value;
  String text;
  ...
}

Now you can write your own renderer by extending BasicComboBoxRenderer. Cast the "value" to "MyData" and render the text.

public class Bla extends BasicComboBoxRenderer{

@Override
public Component getListCellRendererComponent(JList list, Object value,
        int index, boolean isSelected, boolean cellHasFocus) {
    if(value instanceof MyData) {
        setText(((MyData) value).getText());
    }
    return super.getListCellRendererComponent(list, value, index, isSelected,
            cellHasFocus);
}
}

if you use Java7 it is best practice to use generics like @Taiki has shown. Now you can get the selected object by jc.getSelectedItem(). It is always from type MyData and you can access the text ("a", "b", etc.) and the value (1, 2, 3, etc.)