JAVA GUI error message

March 24, 2010

package Lab4;

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;


public class GUI_Element implements ActionListener{
    // Create a frame window

    public static final int WIDTH = 500;
    public static final int HEIGHT = 400;
    public static final int NUMBER_OF_DIGITS = 30;

    private JTextField ioField;
    private double result = 0.0;

    public GUI_Element () {
        JFrame frame = new JFrame ("Mortgage Calculator");
        frame.setSize (WIDTH, HEIGHT);
        frame.setLayout(new GridLayout(7,1,10,10));
}

Okay so I have this java program written. i'm trying to build a GUI for the first time, so just a beginner at this and I'm using Netbeans.

I get this error on the class name GUI_Element

GUI_Element is not abstract and does not override abstract method actionPerformed in java.awt.event.ActionListener

I have no idea why I'm getting this error.

Please help

2,291 · March 24, 2010

I dont mess with gui at all but it could be that you need super() in your constructor as the class is implementing the awt.

^ thats not it.

you could just make the class abstract and implement everything that is needed in your constructor.

public abstract class GUI_Element implements ActionListener{

March 24, 2010

Your class GUI_Element implements an interface (ActionListener). ActionListener requires that implementing classes override the method actionPerformed. You need to define a method called actionPerformed.

It must match the signature in http://java.sun.com/javase/6/docs/api/java/awt/event/ActionListener.html .

so something like:

public void actionPerfomed(ActionEvent e){
   if(e.getSource()==jButton1){
      //do work
   }
}

March 24, 2010

^ Thanks for the suggestions. It works after implementing actionPerformed.

Thank You :)

March 25, 2010

Okay so after adding more code to my file, this is what I ended up with. It looks right to me but the only thing that I need is to make the text field, button smaller so that I can fit the outputs on the same window. I have in all 7 outputs. In the picture I've only shown 2 for now.

Is there a way to make the textfield and button smaller?

Thanks.

March 25, 2010

A GridLayout will make every Component in the Grid the same size no matter what. GridBagLayout will let you set relative sizes, but it's somewhat difficult to figure out. The best bet if you don't want to code the GUI by hand is to use NetBeans IDE. It has a drag-and-drop GUI creator.

Otherwise, you'll want to read this: http://java.sun.com/docs/books/tutorial/uiswing/layout/visual.html

March 26, 2010

^ Thanks for the link. I tried using BorderLayout in mine.

Seems okay to me till now.

Now where I'm stuck is, I want the text "Status of the Program: Waiting for user to enter all the values" to fit on the window. However, my GUI cuts it off. I have no idea how to make it not cut the text I've written.

Any help please?

Thanks :)

March 26, 2010

If you know where it'll be cut off: I believe you can use html tags in a JLabel. So add a <br> and it'll go to a new line. Or use 2 labels. And what are you developing on?

March 26, 2010

I don't quite understand how we use HTML tags. Can you give me a link that will make things more clearer?

I'm building on Netbeans. I have an assignment and its due tomorrow :(. I can't use the Netbeans GUI builder. I have to write all the code myself.

Thanks for the help :)

EDIT:

nvm I found this link:

http://java.sun.com/docs/books/tutorial/uiswing/components/html.html

Thanks for the kind help dontocsata!

EDIT2:

okay still stuck. So I have this:

        status.setText(" &lt;html&gt;&lt;b&gt;Status of the Program: Waiting for user &lt;/b&gt; &lt;b&gt;to enter all the values&lt;/b&gt;");

where status is a JLabel.

HTML doesn't seem to work in this.

I don't really know if I'm right though.

March 26, 2010

The tag for a newline in HTML is <br>

So:

status.setText("Status of the Program: Waiting for user &lt;br&gt;to enter all the values")

Thought it would be better just to make the screen bigger perhaps?

March 26, 2010

^ It worked!

I could make the GUI screen size bigger. But it will only result it to be more stretched out and more empty space on the right which I don't really want.

Thank You kindly!

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JAVA GUI error message

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