Java Get Selected Combobox from Another JFrame

Question

I am a newbie here. Sorry for any bad post or any other bad things.

This question is the continuation of this stackoverflow question. And I already know about the JFrame problem JFrame Bad Practice. The problem is I'm a newbie using Netbeans to code Java. All I know is how to make program with JFrame. Below is the code that I have made. Please help me correct it so the purpose of my code (set Answer class text from TheCombo class selected combobox) can be done.

Please correct this codes (I have 3 classes). I want to get the ComboBox selected Item to be used in the answer class.

Main Class:

package testing;

public class Testing {

    public static void main(String[] args) {
        new TheCombo().setVisible(true);
    }

}

Combo Class:

package testing;

public class TheCombo extends javax.swing.JFrame {

public TheCombo() {
    initComponents();
}

public String getItem()
{
    String theItem = jComboBox1.getSelectedItem().toString();
    return theItem;
}


@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    jComboBox1 = new javax.swing.JComboBox();
    jButton1 = new javax.swing.JButton();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    jComboBox1.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));

    jButton1.setText("Go");
    jButton1.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton1ActionPerformed(evt);
        }
    });

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addComponent(jButton1)
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jButton1))
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
    );

    pack();
}// </editor-fold>                        

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    new Answer().setVisible(true);
    this.dispose();
}                                        

public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(TheCombo.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(TheCombo.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(TheCombo.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(TheCombo.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new TheCombo().setVisible(true);
        }
    });
}

// Variables declaration - do not modify                     
private javax.swing.JButton jButton1;
private javax.swing.JComboBox jComboBox1;
// End of variables declaration                   
}

The Other Class (I want to set text the JTextField1 with selected item from the ComboBox at Combo Class):

package testing;

public class Answer extends javax.swing.JFrame {

TheCombo tc = new TheCombo();

public Answer() {
    initComponents();

    jTextField1.setText(tc.getItem());
}

@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    jTextField1 = new javax.swing.JTextField();
    jButton1 = new javax.swing.JButton();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    jTextField1.setHorizontalAlignment(javax.swing.JTextField.CENTER);
    jTextField1.setEnabled(false);

    jButton1.setText("Back");
    jButton1.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton1ActionPerformed(evt);
        }
    });

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, 50, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
            .addComponent(jButton1)
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jButton1))
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
    );

    pack();
}// </editor-fold>                        

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    new TheCombo().setVisible(true);
    this.dispose();
}                                        

public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(Answer.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(Answer.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(Answer.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(Answer.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new Answer().setVisible(true);
        }
    });
}

// Variables declaration - do not modify                     
private javax.swing.JButton jButton1;
private javax.swing.JTextField jTextField1;
// End of variables declaration                   
}

Use some kind of bridging class, maybe model, which be updated when the comboBox is changed; use an observer pattern to monitor changes in the class with combo box; provide a getter and at some prescribed point in time ask for the value — MadProgrammer, Jan 01 '16 at 06:12
Also based on your code, it highly recommend using a modal dialog to show the combo box class, this way your code will block/wait at the point the dialog is made visible and will continue once it's closed — MadProgrammer, Jan 01 '16 at 06:14
Okay sir, now I'm in the middle of learning observer pattern because I doesn't know anything about that. Thank you sir @MadProgrammer By the way, what's a modal? A Modality? — Arbintoro Mas, Jan 01 '16 at 06:15
Sorry, typing on my phone, it was suppose to be "modal dialog" — MadProgrammer, Jan 01 '16 at 06:16
@MadProgrammer *"highly recommend using a modal dialog to show the combo box class"* See also [The Use of Multiple JFrames, Good/Bad Practice?](http://stackoverflow.com/q/9554636/418556) — Andrew Thompson, Jan 01 '16 at 09:04

score 3 · Answer 1 · answered Jan 01 '16 at 07:41

There are a number of ways you might be able to achieve this, but based on the structure of your code, you seem to be wanting to ask the user a question and then based on the response, do something.

This just screams modal dialog. See How to Make Dialogs for more details

And for example...

import java.awt.EventQueue;
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.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.EmptyBorder;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new QuestionPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class FruitPane extends JPanel {

        private JComboBox<String> cb;

        public FruitPane() {
            add(new JLabel("Fruit: "));
            cb = new JComboBox<String>(new String[]{"Bananas", "Apples", "Pears"});
            add(cb);
        }

        public String getSelectedFruit() {
            return (String) cb.getSelectedItem();
        }

    }

    public class QuestionPane   extends JPanel {

        private JTextField field;

        public QuestionPane() {
            add(new JLabel("Your fruit selection"));
            field = new JTextField(10);
            field.setEditable(false);
            add(field);

            JButton btn = new JButton("Pick");
            add(btn);

            btn.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    FruitPane pane = new FruitPane();
                    pane.setBorder(new EmptyBorder(10, 10, 10, 10));
                    int option = JOptionPane.showConfirmDialog(QuestionPane.this, pane, "Fruit", JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE);
                    if (option == JOptionPane.OK_OPTION) {
                        String fruit = pane.getSelectedFruit();
                        field.setText(fruit);
                    }
                }
            });
        }

    }

}

This is a duplicate question that I just wasted time re-answering since I didn't know that he asked it twice. `` 1+ — Hovercraft Full Of Eels, Jan 01 '16 at 14:00

Java Get Selected Combobox from Another JFrame

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