Fix JButton that is running 2 events

Question

Fix JButton that is running 2 events

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#1 by (2 votes)

2

I have an application where in a JFrame I create new records for a mysql table, and in another I return a select in a JTable with all records created.

I have a button change, which when I select a line from JTable and click on it, opens an instance of the first JFrame to create records, already setting the information of the selected line.

I can update, JoptionPane appears informing that it has been updated, but the application also executes the insertion code, thus creating a new record. The problem is that I can not unlink the button's actionListener, so it first runs the refresh code and then inserts it.

Create record button code:

public class teste3 extends javax.swing.JFrame {

    JButton jbutton;
    public teste3() {
        initComponents();

        this.jbutton = jButton1;
    }

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

        jButton1 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jButton1.setText("jButton1");
        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()
                .addGap(154, 154, 154)
                .addComponent(jButton1)
                .addContainerGap(173, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(121, 121, 121)
                .addComponent(jButton1)
                .addContainerGap(156, Short.MAX_VALUE))
        );

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

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        JOptionPane.showMessageDialog(this, "oi");
    }                                        

    /**
     * @param args the command line arguments
     */
    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(teste3.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(teste3.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(teste3.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(teste3.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 teste3().setVisible(true);
            }
        });
    }

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

code to update:

public class Teste2 extends javax.swing.JFrame {

    teste3 teste3 = new teste3();

    public Teste2() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jButton1 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jButton1.setText("jButton1");
        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()
                .addGap(154, 154, 154)
                .addComponent(jButton1)
                .addContainerGap(173, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(128, 128, 128)
                .addComponent(jButton1)
                .addContainerGap(148, Short.MAX_VALUE))
        );

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

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        teste3 teste3 = new teste3();
        teste3.setVisible(true);

        teste3.jbutton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent ae) {
                JOptionPane.showMessageDialog(teste3, "oi2");
            }
        });
    }                                        

    /**
     * @param args the command line arguments
     */
    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(Teste2.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(Teste2.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(Teste2.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(Teste2.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 Teste2().setVisible(true);
            }
        });
    }

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

java swing actionlistener

asked by anonymous 10.06.2018 / 14:54

1 answer

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score 2 · Accepted Answer

The example added only reinforces what I had already mentioned, that the one causing the problem is you apply a listener inside another listener. In this section of class Teste2 :

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    teste3 teste3 = new teste3();
    teste3.setVisible(true);

    teste3.jbutton.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent ae) {
            JOptionPane.showMessageDialog(teste3, "oi2");
        }
    });
}

You start the other screen and at the same time add a new listener to the new screen button.

Here are two errors: one I've already mentioned, which is to add listener inside another without any type of control, and the other error is the encapsulation violation. If you do not know what this is, I recommend that you read This answer from the same site to better understand.

What happens, in fact, is not the execution twice of the same method, but the execution of the two listeners you apply to the button, because in class teste3 you had already added a listener.

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

...

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    JOptionPane.showMessageDialog(this, "oi");
}

How to correct? Simple! Each window should be responsible for its components and the events that occur within it, so just separate the responsibility of each window within the class itself and not be changing component of one window in the other, as I mentioned, this violates encapsulation and is a bad programming practice, when it is done without having a notion of what that means or the consequences that it can cause.

If jbutton1 belongs to class teste3 , leave everything that is an event only in this class, and apply only ActionListner , since you will hardly need to apply more than one listener of the same type to the same component, this kind of need.

I suggest that you always start with the java tutorials , and there is also the < a href="/ questions / tagged / swing" class="post-tag" title="show questions tagged 'swing'"> swing here on the site with a lot of content because if you want to mess with api swing but you have no idea how it works, you will face this kind of difficulty and continue to make such implementation detrimental to your application.