How to set selected index JComboBox by value

问题

I want to set the selected index in a JComboBox by the value not the index. How to do that? Example

public class ComboItem {

    private String value;
    private String label;

    public ComboItem(String value, String label) {
        this.value = value;
        this.label = label;
    }

    public String getValue() {
        return this.value;
    }

    public String getLabel() {
        return this.label;
    }

    @Override
    public String toString() {
        return label;
    }
}

JComboBox test = new JComboBox();
test.addItem(new ComboItem(0, "orange"));
test.addItem(new ComboItem(1, "pear"));
test.addItem(new ComboItem(2, "apple"));
test.addItem(new ComboItem(3, "banana"));
test.setSelectedItem("banana");

Ok, I have modified my question a bit. I forgot that i have a custom item inside my JComboBox that makes it a bit more difficult. i cant do setSelectedItem as i have a ComboItem inside each item. So still, how do i get this done?

回答1:

setSelectedItem("banana"). You could have found it yourself by just reading the javadoc.

Edit: since you changed the question, I'll change my answer.

If you want to select the item having the "banana" label, then you have two solutions:

Iterate through the items to find the one (or the index of the one) which has the given label, and then call setSelectedItem(theFoundItem) (or setSelectedIndex(theFoundIndex))
Override equals and hashCode in ComboItem so that two ComboItem instances having the same name are equal, and simply use setSelectedItem(new ComboItem(anyNumber, "banana"));

回答2:

public static void setSelectedValue(JComboBox comboBox, int value)
    {
        ComboItem item;
        for (int i = 0; i < comboBox.getItemCount(); i++)
        {
            item = (ComboItem)comboBox.getItemAt(i);
            if (item.getValue().equalsIgnoreCase(value))
            {
                comboBox.setSelectedIndex(i);
                break;
            }
        }
    }

Hope this help :)

回答3:

You should use model

comboBox.getModel().setSelectedItem(object);

回答4:

Why not take a collection, likely a Map such as a HashMap, and use it as the nucleus of your own combo box model class that implements the ComboBoxModel interface? Then you could access your combo box's items easily via their key Strings rather than ints.

For instance...

import java.util.HashMap;
import java.util.Map;

import javax.swing.ComboBoxModel;
import javax.swing.event.ListDataListener;

public class MyComboModel<K, V>   implements ComboBoxModel {
   private Map<K, V> nucleus = new HashMap<K, V>();

   // ... any constructors that you want would go here

   public void put(K key, V value) {
      nucleus.put(key, value);
   }

   public V get(K key) {
      return nucleus.get(key);
   }

   @Override
   public void addListDataListener(ListDataListener arg0) {
      // TODO Auto-generated method stub

   }

   // ... plus all the other methods required by the interface
}

回答5:

for example

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.SwingUtilities;

public class ComboboxExample {

    private JFrame frame = new JFrame("Test");
    private JComboBox comboBox = new JComboBox();

    public ComboboxExample() {
        createGui();
    }

    private void createGui() {
        comboBox.addItem("One");
        comboBox.addItem("Two");
        comboBox.addItem("Three");
        JButton button = new JButton("Show Selected");
        button.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                JOptionPane.showMessageDialog(frame, "Selected item: " + comboBox.getSelectedItem());
                javax.swing.SwingUtilities.invokeLater(new Runnable() {

                    @Override
                    public void run() {
                        comboBox.requestFocus();
                        comboBox.requestFocusInWindow();
                    }
                });
            }
        });
        JButton button1 = new JButton("Append Items");
        button1.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                appendCbItem();
            }
        });
        JButton button2 = new JButton("Reduce Items");
        button2.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                reduceCbItem();
            }
        });
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(new GridLayout(4, 1));
        frame.add(comboBox);
        frame.add(button);
        frame.add(button1);
        frame.add(button2);
        frame.setLocation(200, 200);
        frame.pack();
        frame.setVisible(true);
        selectFirstItem();
    }

    public void appendCbItem() {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                comboBox.addItem("Four");
                comboBox.addItem("Five");
                comboBox.addItem("Six");
                comboBox.setSelectedItem("Six");
                requestCbFocus();
            }
        });
    }

    public void reduceCbItem() {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                comboBox.removeItem("Four");
                comboBox.removeItem("Five");
                comboBox.removeItem("Six");
                selectFirstItem();
            }
        });
    }

    public void selectFirstItem() {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                comboBox.setSelectedIndex(0);
                requestCbFocus();
            }
        });
    }

    public void requestCbFocus() {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                comboBox.requestFocus();
                comboBox.requestFocusInWindow();
            }
        });
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                ComboboxExample comboboxExample = new ComboboxExample();
            }
        });
    }
}

回答6:

http://docs.oracle.com/javase/6/docs/api/javax/swing/JComboBox.html#setSelectedItem(java.lang.Object)

test.setSelectedItem("banana");

There are some caveats or potentially unexpected behavior as explained in the javadoc. Make sure to read that.

回答7:

The right way to set an item selected when the combobox is populated by some class' constructor (as @milosz posted):

combobox.getModel().setSelectedItem(new ClassName(parameter1, parameter2));

In your case the code would be:

test.getModel().setSelectedItem(new ComboItem(3, "banana"));

回答8:

public boolean  preencherjTextCombox (){
       int x = Integer.parseInt(TableModelo.getModel().getValueAt(TableModelo.getSelectedRow(),0).toString());

       modeloobj = modelosDAO.pesquisar(x);
       Combmarcass.getModel().setSelectedItem(modeloobj.getMarca());  
       txtCodigo.setText(String.valueOf(modeloobj.getCodigo()));
       txtDescricao.setText(String.valueOf(modeloobj.getDescricao()));
       txtPotencia.setText(String.valueOf(modeloobj.getPotencia()));  

       return true;
   }

回答9:

Just call comboBox.updateUI() after doing comboBox.setSelectedItem or comboBox.setSelectedIndex or comboModel.setSelectedItem

来源：https://stackoverflow.com/questions/8327352/how-to-set-selected-index-jcombobox-by-value

标签

java

swing

jcombobox

selectedindex