Handling Multiple Events

• As long as we're using objects, we should think about how to re-use code.
• So, let's add a few more components to our class.
• The two Click Me buttons on this form are different objects.  But, they share the same listener.

 
• Note the green text in the source code below.
• This shows that, we only have one listener class, but we're re-using it on two different components.
• We're able to dynamically use the components to set the text when the button is clicked.  Thus, we could add as many components as we wish, and never have to change the listener!

/**
 *
 * @author  default
 */
public class MultipleComponents extends javax.swing.JFrame {

    /** Creates new form FirstEvent */
    public MultipleComponents() {
        initComponents();
        // We have two buttons.  Let's make two listener objects, and instantiate
        // each with unique objects.  This will allow us to re-use the class, but
        // still tailor it for each button.  Alas, object oriented programming.
        btnClickMe1.addActionListener(new MyListener(txtEnter1, lblDisplay1));
        btnClickMe2.addActionListener(new MyListener(txtEnter2, lblDisplay2));
    }

    /** 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.
     */
    private void initComponents() {
        jPanel1 = new javax.swing.JPanel();
        lblEnter1 = new javax.swing.JLabel();
        txtEnter1 = new javax.swing.JTextField();
        btnClickMe1 = new javax.swing.JButton();
        lblDisplay1 = new javax.swing.JLabel();
        jPanel11 = new javax.swing.JPanel();
        lblEnter2 = new javax.swing.JLabel();
        txtEnter2 = new javax.swing.JTextField();
        btnClickMe2 = new javax.swing.JButton();
        lblDisplay2 = new javax.swing.JLabel();

        getContentPane().setLayout(new java.awt.FlowLayout());

        addWindowListener(new java.awt.event.WindowAdapter() {
            public void windowClosing(java.awt.event.WindowEvent evt) {
                exitForm(evt);
            }
        });

        jPanel1.setLayout(new java.awt.GridLayout(1, 0));

        lblEnter1.setText("Enter some text.");
        lblEnter1.setName("lblEnter");
        jPanel1.add(lblEnter1);

        txtEnter1.setName("txtEnter");
        jPanel1.add(txtEnter1);

        btnClickMe1.setText("Click Me");
        btnClickMe1.setName("btnClickMe");
        jPanel1.add(btnClickMe1);

        lblDisplay1.setName("lblResult");
        jPanel1.add(lblDisplay1);

        getContentPane().add(jPanel1);

        jPanel11.setLayout(new java.awt.GridLayout());

        lblEnter2.setText("Enter some text.");
        lblEnter2.setName("lblEnter2");
        jPanel11.add(lblEnter2);

        txtEnter2.setName("txtEnter2");
        jPanel11.add(txtEnter2);

        btnClickMe2.setText("Click Me");
        btnClickMe2.setName("btnClickMe2");
        jPanel11.add(btnClickMe2);

        lblDisplay2.setName("lblResult");
        jPanel11.add(lblDisplay2);

        getContentPane().add(jPanel11);

        pack();
    }

    /** Exit the Application */
    private void exitForm(java.awt.event.WindowEvent evt) {
        System.exit(0);
    }

    /**
    * @param args the command line arguments
    */
    public static void main(String args[]) {
        new MultipleComponents().show();
    }
 

    // Variables declaration - do not modify
    private javax.swing.JLabel lblDisplay1;
    private javax.swing.JPanel jPanel11;
    private javax.swing.JButton btnClickMe2;
    private javax.swing.JButton btnClickMe1;
    private javax.swing.JLabel lblEnter2;
    private javax.swing.JLabel lblEnter1;
    private javax.swing.JTextField txtEnter2;
    private javax.swing.JTextField txtEnter1;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JLabel lblDisplay2;
    // End of variables declaration

    // A listener class that we re-use for both parts of the form.
    class MyListener implements java.awt.event.ActionListener {

            javax.swing.JTextField source;
            javax.swing.JLabel destination;

            MyListener(javax.swing.JTextField source, javax.swing.JLabel destination) {
                 this.source = source;
                 this.destination = destination;
            }

            public void actionPerformed(java.awt.event.ActionEvent evt) {
                destination.setText(source.getText());
            }
    }

}
 

 Multicasting - doing the opposite
 

Created by:  Brandan Jones January 4, 2002