Popular combobox inside jtable with database, how to proceed?

Question

Currently I populate a normal combobox this way:

this.CadperfilLinha.removeAllItems();
try {
    Class.forName(Auxiliar.AcessoBanco.getDriver());
    Connection con = DriverManager.getConnection(Auxiliar.AcessoBanco.getUrl(), Auxiliar.AcessoBanco.getUser(), Auxiliar.AcessoBanco.getPass());;
    Statement Sent = con.createStatement();
    ResultSet rs = Sent.executeQuery("Select * from Linha");
    CadperfilLinha.addItem("Selecione...");
    while (rs.next()) {
        this.CadperfilLinha.addItem(rs.getString("LINHA"));
    }
} catch (Exception e) {
    JOptionPane.showMessageDialog(null, e);
}

But now I’m needing to popular one inside the jtable, but I’m not getting it. I have it mounted here pulling only typed values inside the code and wanted it to use the database. Someone can give me a hand?

String[] values = new String[]{"Ativo", "Desativado"};

TableColumn col = jTable1.getColumnModel().getColumn(2);
col.setCellEditor(new MyComboBoxEditor(values));
col.setCellRenderer(new MyComboBoxRenderer(values));

class MyComboBoxRenderer extends JComboBox implements TableCellRenderer {

    public MyComboBoxRenderer(String[] items) {
        super(items);
    }

    public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected,
            boolean hasFocus, int row, int column) {
        if (isSelected) {
            setForeground(table.getSelectionForeground());
            super.setBackground(table.getSelectionBackground());
        } else {
            setForeground(table.getForeground());
            setBackground(table.getBackground());
        }
        setSelectedItem(value);
        return this;
    }
}

class MyComboBoxEditor extends DefaultCellEditor {

    public MyComboBoxEditor(String[] items) {
        super(new JComboBox(items));
    }
}

Answer 1

If you need to popular a JComboBox with database data and want to isolate this fill, the best I can recommend is to create a ComboBoxModel and fill out the bank on his builder. a Comboboxmodel is nothing more than a template to fill a Jcombobox, when you create a combo and do combo.addItem(), what actually happens is the filling of a standard internal model created for the component, this standard model is the class DefaultComboBoxModel.

An example of how to create could be as below:

class MeuComboModel extends DefaultComboBoxModel {

    private ArrayList<String> itens;
    private Object itemSelected;

    public MeuComboModel() {
        this.itens = new ArrayList<>();
        this.itens.add("Option 1");
        this.itens.add("Option 2");
        this.itens.add("Option 3");
        this.itens.add("Option 4");
    }

    @Override
    public int getSize() {
        return itens.size();
    }

    @Override
    public Object getElementAt(int index) {
        return itens.get(index);
    }

    @Override
    public void setSelectedItem(Object anItem) {
        this.itemSelected = anItem;

    }

    @Override
    public Object getSelectedItem() {
        return this.itemSelected;
    }
}

I created a class inheriting from DefaultComboBoxModelso we need to set up as little as possible. In this case I am directly populating, but just assign the items coming from the bank in the list instead.

To assign the model to the combo, you can either start already passing an instance of it or set later through the method setModel():

• Method 1 :

  JComboBox combo = new JComboBox(new MeuComboModel());
  

• Method 2:

  seucombo.setModel(new MeuComboModel());
  

Until now, the combo is already filled, and if the items are Strings or some primitive type of java, depending on the model your table uses, just pass this combo to an instance of the class DefaultTableCellEditor:

this.table.getColumnModel().getColumn(<<indice da coluna>>).setCellEditor(new DefaultCellEditor(comboBox));

With this, the combo is displayed correctly when its cell goes into edit mode, the option selected as well, as can be seen below:

If you want to read more about it, I recommend the official documentation tutorials: How to Use Tables and How to Use Combo Boxes.