How to use Map element as text of a JComboBox
(2) specify how these objects are to appear in the GUI.
You can add any Object to the model and then create a custom renderer to display the object any way you want. Simple example that shows the toString() approach and custom renderer approach:
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.plaf.basic.*;
public class ComboBoxItem extends JFrame implements ActionListener
{
public ComboBoxItem()
{
Vector model = new Vector();
model.addElement( new Item(1, "car" ) );
model.addElement( new Item(2, "plane" ) );
model.addElement( new Item(3, "train" ) );
model.addElement( new Item(4, "boat" ) );
JComboBox comboBox;
// Easiest approach is to just override toString() method
// of the Item class
comboBox = new JComboBox( model );
comboBox.setDragEnabled(true);
comboBox.addActionListener( this );
getContentPane().add(comboBox, BorderLayout.NORTH );
// Most flexible approach is to create a custom render
// to diplay the Item data
comboBox = new JComboBox( model );
comboBox.setDragEnabled(true);
comboBox.setRenderer( new ItemRenderer() );
comboBox.addActionListener( this );
getContentPane().add(comboBox, BorderLayout.SOUTH );
}
public void actionPerformed(ActionEvent e)
{
JComboBox comboBox = (JComboBox)e.getSource();
Item item = (Item)comboBox.getSelectedItem();
System.out.println( item.getId() + " : " + item.getDescription() );
}
class ItemRenderer extends BasicComboBoxRenderer
{
public Component getListCellRendererComponent(
JList list, Object value, int index,
boolean isSelected, boolean cellHasFocus)
{
super.getListCellRendererComponent(list, value, index,
isSelected, cellHasFocus);
if (value != null)
{
Item item = (Item)value;
setText( item.getDescription().toUpperCase() );
}
if (index == -1)
{
Item item = (Item)value;
setText( "" + item.getId() );
}
return this;
}
}
class Item
{
private int id;
private String description;
public Item(int id, String description)
{
this.id = id;
this.description = description;
}
public int getId()
{
return id;
}
public String getDescription()
{
return description;
}
public String toString()
{
return description;
}
}
public static void main(String[] args)
{
JFrame frame = new ComboBoxItem();
frame.setDefaultCloseOperation( EXIT_ON_CLOSE );
frame.pack();
frame.setVisible( true );
}
}
llm
Updated on June 04, 2022Comments
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llm about 2 years
I am populating a JComboBox (using
addItem()
) with all the elements of a collection. Each element in the collection is aHashMap
(so its a ComboBox of Hashmaps..).My question is - Given that I need each item to be a
HashMap
how do I set the text to apear in the combobox on the GUI? It needs to be the value of a certain key in the map. Normally if I am populating a combobox with my own type, I would just overide thetoString()
method...but I am not sure how to acheive this since I am using a Java HashMap.Any ideas (if possible, without implementing my own HashMap)?
Update: It seems like there isn't anyway to avoid having the object int the JComboBox overide toString() if I want custom functionality..I wish there was a way to (1) specify the objects to be loaded into the JComboBox and (2) specify how these objects are to appear in the GUI.
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llm about 14 yearsyes, I was really hoping to avoid this if possible..but thanks for the suggestion
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Andrew Hubbs about 14 yearsUnless I misunderstood the OP this is not the situation. He has new JComboBox(someCollection<HashMap>); rather than just wanting the values of a single HashMap.