redesign so each button has it’s own listener. Each listener has it’s own class.

Question

redesign so each button has it’s own listener. Each listener has it’s own class. Class must implement action listener interface.

//********************************************************************

// LeftRightPanel.java       Authors: Lewis/Loftus

//

// Demonstrates the use of one listener for multiple buttons.

//********************************************************************

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class LeftRightPanel extends JPanel

{

   private JButton left, right;

   private JLabel label;

   private JPanel buttonPanel;

//-----------------------------------------------------------------

   // Constructor: Sets up the GUI.

   //-----------------------------------------------------------------

   public LeftRightPanel()

   {

      left = new JButton("Left");

      right = new JButton("Right");

      ButtonListener listener = new ButtonListener();

      left.addActionListener(listener);

      right.addActionListener(listener);

      label = new JLabel("Push a button");

      buttonPanel = new JPanel();

      buttonPanel.setPreferredSize(new Dimension(200, 40));

      buttonPanel.setBackground(Color.blue);

      buttonPanel.add(left);

      buttonPanel.add(right);

      setPreferredSize(new Dimension(200, 80));

      setBackground(Color.cyan);

      add(label);

      add(buttonPanel);

   }

//*****************************************************************

   // Represents a listener for both buttons.

   //*****************************************************************

   private class ButtonListener implements ActionListener

   {

      //--------------------------------------------------------------

      // Determines which button was pressed and sets the label

      // text accordingly.

      //--------------------------------------------------------------

      public void actionPerformed(ActionEvent event)

      {

         if (event.getSource() == left)

            label.setText("Left");

         else

            label.setText("Right");

      }

   }

}

Explanation / Answer

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class LeftRightPanel extends JPanel

{

   private JButton left, right;

   private JLabel label;

   private JPanel buttonPanel;

   //-----------------------------------------------------------------

   // Constructor: Sets up the GUI.

   //-----------------------------------------------------------------

   public LeftRightPanel()

   {

      left = new JButton("Left");

      right = new JButton("Right");

      LeftClickListener leftClickListener = new LeftClickListener();
      left.addActionListener(leftClickListener);
      RightClickListener rightClickListener = new RightClickListener();
      right.addActionListener(rightClickListener);

      label = new JLabel("Push a button");

      buttonPanel = new JPanel();

      buttonPanel.setPreferredSize(new Dimension(200, 40));

      buttonPanel.setBackground(Color.blue);

      buttonPanel.add(left);

      buttonPanel.add(right);

      setPreferredSize(new Dimension(200, 80));

      setBackground(Color.cyan);

      add(label);

      add(buttonPanel);

   }

   private class LeftClickListener implements ActionListener{
      public void actionPerformed(ActionEvent event)
         {
               label.setText("Left");
         }
   }

   private class RightClickListener implements ActionListener{
      public void actionPerformed(ActionEvent event)
         {
               label.setText("Right");
         }
   }

}

Related Questions

Navigate

• Browse (All)
• Browse R
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.