The type must implement the inherited abstract method???

Question

import java.awt.*;
import java.awt.event.*;
import java.awt.ActiveEvent;
import java.applet.*;
public class MoveIt extends Applet implements ActionListener
     private Image cup;
     private Panel keyPad;
     public int yaxis = 15;
     public int xaxis = 15;
     private Button keysArray[];
     public void init()
          cup = getImage(getDocumentBase(), "cup.gif");
          Canvas myCanvas = new Canvas();
          setBackground(Color.blue);
          setLayout(new BorderLayout());
          Button up = new Button("Up");
          Button down = new Button("Down");
          Button right = new Button("Right");
          Button left = new Button("Left");
          Button center = new Button("Center");
          add(myCanvas, BorderLayout.NORTH);
          add(keyPad, BorderLayout.SOUTH);
          keyPad.add(up, BorderLayout.NORTH);
          up.addActionListener(this);
          keyPad.add(down, BorderLayout.SOUTH);
          down.addActionListener(this);
          keyPad.add(right, BorderLayout.EAST);
          right.addActionListener(this);
          keyPad.add(left, BorderLayout.WEST);
          left.addActionListener(this);
          keyPad.add(center, BorderLayout.CENTER);
          center.addActionListener(this);
     public void paint( Graphics g )
          g.drawImage( cup, xaxis, yaxis, this );
     public void ActionPerformed(ActionEvent e)
          String action = e.getActionCommand();
          if(action.equals("Up"))
               yaxis = yaxis - 15;
          if(action.equals("Down"))
               yaxis = yaxis + 15;
          if(action.equals("Left"))
               xaxis = xaxis - 15;
          if(action.equals("Right"))
               xaxis = xaxis + 15;
          if(action.equals("Center"))
               xaxis = 125;
               yaxis = 60;
}How come there is an error:
The type MoveIt must implement the inherited abstract method
ActionListener.actionPerformed(ActionEvent)
What the hell does that mean?

Answer 1

A class that implements an interface must define the methods of the interface. Your applet (or the one you borrowed) states at the top that it implements the ActionListener interface. If you go to the API, you'll see that this interface declares a method "actionPerformed", and so this class must have a method that matches the one in the interface. I see that your applet will have some Buttons. You'll need an actionPerformed method if you want the buttons to use your class (this) as their action listener.
Edit: I see that you already have an "ActionPerformed" method, but note that case matters, and this is not the same as "actionPerformed". Change one letter and you're on your way.
Edited by: Encephalopathic on Jan 15, 2008 8:44 PM