Question

I had a huge file for creating this GUI and I have shortened it by using arrays. I am trying to add an ActionListener but when the arrays are being added and I am getting the following errors:

/tmp/jc_3531/GUI.java:60: addActionListener(java.awt.event.ActionListener) in javax.swing.AbstractButton cannot be applied to (GUI)
            nButtons[c].addActionListener( this );
                       ^
/tmp/jc_3531/GUI.java:69: cannot find symbol
symbol  : method addActionListener(GUI)
location: class javax.swing.JLabel
            labels[c].addActionListener( this );
                     ^
/tmp/jc_3531/GUI.java:78: addActionListener(java.awt.event.ActionListener) in javax.swing.JTextField cannot be applied to (GUI)
            fields[c].addActionListener( this );
                     ^
/tmp/jc_3531/GUI.java:90: addActionListener(java.awt.event.ActionListener) in javax.swing.AbstractButton cannot be applied to (GUI)
            sButtons[c].addActionListener( this );
                       ^
4 errors

What am I doing wrong? Is there an easier way to self diagnose (like an editor with an integrated syntax guide)?

Here is my Code

// GUI with navigation amd file manipulation buttons
import javax.swing.*; // provides basic window features
import java.awt.event.*;
import java.awt.GridLayout;
import java.awt.BorderLayout;
import java.text.NumberFormat;

public class GUI extends JFrame 
{
    private Inventory inv;      
    private int currentDisplay = 0; 

    private JPanel nButtonJPanel;
    private String nNames[]={"Load","Add","Modify","Delete","Search","Save"};
    private JButton nButtons[];

    private JPanel labelJPanel;
    private String labeled[]={"Item ID","Name","Rating","# in Stock","Price","Inventory Value",
    "Restocking Fee (5%)","Inventory Value with Fee","Total Value with Fee (all DVD's)"};
    private JLabel labels[];

    private JPanel fieldJPanel;
    private String fieldsBlank[]={"","","","","","","","",""};
    private JTextField fields[];

    private JPanel sButtonJPanel;
    private String sNames[]={"First","Prev","","Next","Last"};
    private JButton sButtons[];

   // LabelFrame constructor adds JLabels to JFrame
   public GUI()
   {
      super( "Inventory Program v.5" );
      setLayout( new BorderLayout() ); // set frame layout

        // initialize values
        RatedDVD d1 = new RatedDVD(1, "One Flew Over The Cuckoo's Nest", 3, 9.99, "PG");
        RatedDVD d2 = new   RatedDVD(2, "The Matrix", 1, 13.01, "PG13");
        RatedDVD d3 = new   RatedDVD(3, "Se7en", 7, 11.11, "R");
        RatedDVD d4 = new   RatedDVD(4, "Oceans Eleven", 11, 9.02, "PG13");
        RatedDVD d5 = new   RatedDVD(5, "Hitch Hikers Guide to the Galaxy", 42, 10.00, "G");    
        RatedDVD d6 = new   RatedDVD(6, "The Invisible Man", 0, 4999.59, "G");  

        // create inv and enter values
        inv = new Inventory();
        inv.add(d1);
        inv.add(d2);
        inv.add(d3);
        inv.add(d4);
        inv.add(d5);
        inv.add(d6);

        inv.sort();

        //make nButtons
        nButtonJPanel.setLayout( new GridLayout( 1, nNames.length, 5, 5 ) );
        nButtons=new JButton[nNames.length];
        for(int c=0;c<nButtons.length;c++){
            nButtons[c]=new JButton(nNames[c]);
            nButtons[c].addActionListener( this );
            nButtonJPanel.add(nButtons[c]); }
        add( nButtonJPanel, BorderLayout.NORTH );

        //make labels
        labelJPanel.setLayout( new GridLayout( labeled.length, 1 ));
        labels=new JLabel[labeled.length];  
        for(int c=0;c<labels.length;c++){
            labels[c]=new JLabel(labeled[c]);
            labels[c].addActionListener( this );
            labelJPanel.add(labels[c]);}
        add( labelJPanel, BorderLayout.WEST );

        //make fields
        fieldJPanel.setLayout( new GridLayout( fieldsBlank.length, 1 ));
        fields=new JTextField[fieldsBlank.length];
        for(int c=0;c<fields.length;c++){
            fields[c]=new JTextField(fieldsBlank[c],28);
            fields[c].addActionListener( this );
            fields[c].setEditable(false);
            fieldJPanel.add(fields[c]); }
            populate(currentDisplay);
        add( fieldJPanel, BorderLayout.EAST );

        //make sButtons
        sButtonJPanel.setLayout( new GridLayout( 1, sNames.length, 5, 5 ) );
        sButtons=new JButton[sNames.length];    
        Icon dvd50 = new ImageIcon( getClass().getResource( "dvd50.jpg" ) );
        for(int c=0;c<sButtons.length;c++){
            sButtons[c]=new JButton(sNames[c]);
            sButtons[c].addActionListener( this );
            sButtonJPanel.add(sButtons[c]);}
        sButtons[2].setIcon( dvd50 );       
        add( sButtonJPanel, BorderLayout.SOUTH );
    }// end method

    public void populate(int currentDisplay)
    {
    NumberFormat nf = NumberFormat.getCurrencyInstance();
    fields[0].setText(String.valueOf(inv.get(currentDisplay).getItem()));
    fields[1].setText(inv.get(currentDisplay).getName());
    fields[2].setText(inv.get(currentDisplay).getRating());
    fields[3].setText(String.valueOf(inv.get(currentDisplay).getUnits()));
    fields[4].setText(String.valueOf(nf.format(inv.get(currentDisplay).getPrice())));
    fields[5].setText(String.valueOf(nf.format(inv.get(currentDisplay).value())));
    fields[6].setText(String.valueOf(nf.format(inv.get(currentDisplay).fee())));
    fields[7].setText(String.valueOf(nf.format(inv.get(currentDisplay).feeValue())));
    fields[8].setText(String.valueOf(nf.format(inv.value())));
    }

    public void actionPerformed(ActionEvent e) {


    }

Answer 1

You need to make your GUI class implement ActionListener by changing

public class GUI extends JFrame 

to

public class GUI extends JFrame implements ActionListener