How to fill a Java box combo from another class Using MySql

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How to fill a Java box combo from another class Using MySql

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#1 by (2 votes)

1

It turns out that I created a class with java interface in conjunction with NetBeans. Well I have a combo that filled it with the result of a query but when opening a new frame I insert a data to mysql and when it closes I want it to update automatically. I already tried with a windows close event but it does not. Here I leave my code:

//este método lo uso para llenar el combo con una consulta MySQL
//esta es la clase Alta.java
void llena_combo() {

    try {
        jComboBox1.removeAllItems();
        jComboBox3.removeAllItems();
        jComboBox2.removeAllItems();
        Statement st=cn.createStatement();
        ResultSet rs=st.executeQuery("Select * from unidades");
        while(rs.next())
        {                
            jComboBox1.addItem(rs.getString("unidad"));
            jComboBox3.addItem(rs.getString("unidad"));
            jComboBox2.addItem(rs.getString("unidad"));

        }
    } catch (SQLException ex) {
        Logger.getLogger(Alta.class.getName()).log(Level.SEVERE, null, ex);
        JOptionPane.showMessageDialog(null,ex);
    }     
}

//Ahora en la clase Unidades.java inserto datos y quiero que cuando el usuario cierre la ventana se actualce automaticamente el combo de la clase Alta.java ya lo intente con el evento

private void formWindowClosed(java.awt.event.WindowEvent evt) {                                  
      Alta fr = new Alta();
      fr.llena_combo();
}
//como pueden observar genero un objeto de la clase Alta y ese objeto manda a traer al metodo llena_combo pero no lo hace incluso probe meter el metodo jCombobox.removeAllItems() y si lo hace pero no me explico por que no quiere actualizar mi con el metodo para llenar el combo 
//EL combobox es public static pero no hace nada

mysql java combobox

asked by Anahi Rosas Trejo 14.09.2016 в 03:02

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1 answer

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score 2 · Accepted Answer

You must not use multiple JFrame . An application should have only one. You MUST use a JDialog of for daughters windows.

public class Form2 extends JDialog{...}

It is the responsibility of the daughter window to update So when the "Save" button in the dialog box is clicked. The code ActionListener has to do two things:

Update the database with the new value

Update the combo box with the new value. So this means that when you create the JDialog you need to approve the combo box (or the ComboBoxModel) as a parameter to that class so you can update the combo box. Or, what you need to return a value from the dialog so that when the dialog is closed you can update the combo box.

It is recommended to add elements to your combo through a model for example DefaultComboBoxModel

static DefaultComboBoxModel modelo;//declarar static e instanciarla en tu contructor'
public Jfram1() {
    initComponents();
    modelo = new DefaultComboBoxModel();
   llena_combo(); // llenar los datos al ejecutar el programa
}

Your method to fill in a combo could be something like this

static void llena_combo(){ // static para poder llamarlo desde el otro frame o JDialog

try {
    modelo.removeAllElements(); // eliminamos lo elementos
    Statement st=cn.createStatement();
    ResultSet rs=st.executeQuery("Select * from unidades");
    while(rs.next())
    {                
        modelo.addElement(rs.getString("unidad"));
    }
     combo.setModel(modelo); // seteamos el modelo y se cargan los datos
} catch (SQLException ex) {
    Logger.getLogger(Alta.class.getName()).log(Level.SEVERE, null, ex);
    JOptionPane.showMessageDialog(null,ex);
}

and the windowClosing event of your second form where you add the data to the database would be

public void windowClosing(java.awt.event.WindowEvent windowEvent) {
        if (JOptionPane.showConfirmDialog(null, 
            "Está seguro que desea Salir?", "Desea Salir?", 
            JOptionPane.YES_NO_OPTION,
            JOptionPane.QUESTION_MESSAGE) == JOptionPane.YES_OPTION){
            dispose();
            Jfram1.llenarCombo();
        }