How to set index when inserting item in Jcombobox?

Question

I wonder if someone could help me. I’m trying to add items to a JComboBox:

Pessoa carlos = new Pessoa(12, "Carlos" , 0.0f);
jComboBoxF.addItem(carlos.getNome());
Pessoa maria = new Pessoa(23, "Maria" ,0.0f);
jComboBoxF.addItem(maria.getNome());

In this case the JComboBox is in the index "0" as the value "Carlos", and in the index "1" with the value Maria.

What I would like to know is whether adding the name was also possible to add the index, in order to be in this case with two identifiers 12 and 23, 12 for the value Carlos and 23 for the value Maria.

In other words I want to use the People id’s as the JComboBox.

What I want with this is to use the index of JComboBox to identify the Person in question, since the index of the combo in this way would be the Person’s own ID.

Answer 1

André,

if you are using a model in his JComboBox that implements the interface MutableComboBoxModel you’ll manage to make:

((MutableComboBoxModel) jComboBox.getModel()).insertElementAt(carlos, 0);
((MutableComboBoxModel) jComboBox.getModel()).insertElementAt(maria, 1);

But I strongly advise you to create the list of items before putting in your JComboBox, something like:

List<Pessoa> pessoas = new ArrayList<>();
pessoas.add(new Pessoa(12, "Carlos" , 0.0f));//adicionando o carlos na lista
pessoas.add(new Pessoa(23, "Maria" ,0.0f));

//com a lista pronta, altere o model no seu jComboBox
jComboBox.setModel(new DefaultComboBoxModel<>(pessoas.toArray()));

When you say you want the index to be 12 or 23, it will only be possible if you have more than 23 items in your jComboBox. The index in the case is the position the element is in its jComboBox, 0 being the first position up to list size -1.

What you might want is to display these numbers next to the name on your jComboBox. For this you only need to overwrite the method toString() in your class Pessoa.

public class Pessoa{

  private String nome;
  private int idade;

  @Override
  public String toString(){
    return idade + " - " + nome;
  }

}

So yours jComboBox will display the items like this:

• 12 - Carlos
• 23 - Mary

Answer 2

Here is a functional example of what you want. Basically the secret is to implement the method toString() adequately.

package testes;

import java.awt.EventQueue;
import java.awt.FlowLayout;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JOptionPane;

public class TesteComboBox {
    public static void main(String[] args) {
        EventQueue.invokeLater(TesteComboBox::exemplo);
    }

    private static void exemplo() {
        JFrame jf = new JFrame("Exemplo");
        JComboBox<Pessoa> jComboBoxF = new JComboBox<>();
        jf.setLayout(new FlowLayout());
        jf.add(jComboBoxF);

        Pessoa carlos = new Pessoa(12, "Carlos", 0.0f);
        Pessoa maria = new Pessoa(23, "Maria", 0.0f);
        jComboBoxF.addItem(carlos);
        jComboBoxF.addItem(maria);

        JButton mensagem = new JButton("Mostrar");
        jf.add(mensagem);
        mensagem.addActionListener(e -> {
            int idx = jComboBoxF.getSelectedIndex();
            if (idx == -1) {
                JOptionPane.showMessageDialog(jf, "Você não escolheu ninguém.");
            } else {
                Pessoa escolha = jComboBoxF.getItemAt(jComboBoxF.getSelectedIndex());
                JOptionPane.showMessageDialog(jf, "Você escolheu " + escolha.getNome() + " de id " + escolha.getId());
            }
        });

        jf.pack();
        jf.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        jf.setVisible(true);
    }

    public static class Pessoa {
        private final int id;
        private final String nome;
        private final double outraCoisa;

        public Pessoa(int id, String nome, double outraCoisa) {
            this.id = id;
            this.nome = nome;
            this.outraCoisa = outraCoisa;
        }

        public int getId() {
            return id;
        }

        public String getNome() {
            return nome;
        }

        public double getOutraCoisa() {
            return outraCoisa;
        }

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

If the object you want to add on the combobox cannot have a method toString() suitable, so use an auxiliary class with the toString() suitable:

public class MinhaClasseAuxiliar {
    private final Pessoa p;
    public MinhaClasseAuxiliar(Pessoa p) {
        this.p = p;
    }

    public Pessoa getPessoa() {
        return p;
    }

    @Override
    public String toString() {
        // Aqui você faz o que quiser.
    }
}

And then you add tweaks from the auxiliary class instead of adding Pessoa.

Answer 3

I understand your doubt! However, I don’t know if this will still be good for you after so long, but suddenly it might be good for someone else. In this link there is something that can serve you: http://www.linhadecodigo.com.br/artigo/1891/adicionado-objetos-a-combobox.aspx