Programming Forums > Application Development > Java

Intimidat0r · Mar 10th, 2007, 6:03 PM

I'm just starting out with learning about Swing, and I'm running into some trouble already. Basically what's happening is I'm trying to make an array of 9 buttons (well a 3x3 array) but, well, let me show you:

(Toggle Plain Text)

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

public class guiTest implements ActionListener { //error 1
	private static JButton[] bbox;

	public static void main(String args[]) {
		JPanel panel = new JPanel();
		panel.setLayout(new GridLayout(3,3));
		bbox = new JButton[9];
		for (int h = 0; h < 9; h++) {
			panel.add(bbox[h]);
			bbox[h].addActionListener(this); //error 2
		}
		Container c = getContentPane(); //error 3
		c.add(panel, BorderLayout.CENTER);
		JFrame f = new JFrame("GUI Test!!!");
		f.add(c);
		}
	}
}

I've commented the three lines in which the following three errors are reported by the compiler:

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guiTest is not abstract and does not override abstract method actionPerformed(java.awt.event.ActionEvent) in java.awt.event.ActionListener
public class guiTest implements ActionListener {
       ^
non-static variable this cannot be referenced from a static context
            bbox[h].addActionListener(this);
                                                  ^
cannot find symbol
symbol  : method getContentPane()
location: class TicTacToe
        Container c = getContentPane();
                              ^

Any help? Thanks in advance!

Arevos · Mar 10th, 2007, 7:27 PM

Why are you inheriting from ActionListener?

titaniumdecoy · Mar 10th, 2007, 8:29 PM

No offense, but the multitude of fundamental problems with your code most likely indicates that your understanding of the Java language is insufficient to be working with GUIs. Instead of taking the time to write out an explanation for each problem, I rewrote the code for you to study.

(Toggle Plain Text)

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

public class GUITest extends JFrame implements ActionListener {
    private static JButton[] bbox;
    
    public GUITest() {
        
        super("GUI Test");
        
        setLayout(new GridLayout(3,3));
        
        bbox = new JButton[9];
        
        for (int i = 0; i < bbox.length; i++) {
            bbox[i] = new JButton(Integer.toString(i));
            bbox[i].addActionListener(this);
            add(bbox[i]);
        }
        
        pack();
        
        setVisible(true);
        
    }

    public static void main(String args[]) {
        new GUITest();
    }

    public void actionPerformed(ActionEvent evt) {
        // This method is called when a button is clicked
    }
    
}

Intimidat0r · Mar 10th, 2007, 10:36 PM

Thanks. I am pretty new to Java. Let me ask you one more thing? Is there a way (presumably in actionPerformed()) to tell which button of the array was clicked? Or do I have to use a different method for each one?

titaniumdecoy · Mar 10th, 2007, 10:42 PM

I prefer to use the getSource() method of the ActionEvent object:

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public void actionPerformed(ActionEvent evt) {
    if (evt.getSource() == bbox[0]) {
        // bbox[0] was pressed
    }
}

You can get the name of the button with the getActionCommand() method, but remember that if you change the button's text, that change will be reflected in the value returned by this function.

(Toggle Plain Text)

public void actionPerformed(ActionEvent evt) {
    if (evt.getActionCommand().equals("0")) {
        // The button labeled "0" was pressed
    }
}

Intimidat0r · Mar 10th, 2007, 10:48 PM

Alright, thanks man.

Mar 10th, 2007, 6:03 PM	#1
Intimidat0r Hobbyist Programmer Join Date: May 2005 Location: Don't know, but the padded walls are a nice touch. Posts: 126 Rep Power: 0	Having difficulty with Swing. I'm just starting out with learning about Swing, and I'm running into some trouble already. Basically what's happening is I'm trying to make an array of 9 buttons (well a 3x3 array) but, well, let me show you: (Toggle Plain Text) import java.awt.; import java.awt.event.; import javax.swing.; public class guiTest implements ActionListener { //error 1 private static JButton[] bbox; public static void main(String args[]) { JPanel panel = new JPanel(); panel.setLayout(new GridLayout(3,3)); bbox = new JButton[9]; for (int h = 0; h < 9; h++) { panel.add(bbox[h]); bbox[h].addActionListener(this); //error 2 } Container c = getContentPane(); //error 3 c.add(panel, BorderLayout.CENTER); JFrame f = new JFrame("GUI Test!!!"); f.add(c); } } } import java.awt.; import java.awt.event.; import javax.swing.; public class guiTest implements ActionListener { //error 1 private static JButton[] bbox; public static void main(String args[]) { JPanel panel = new JPanel(); panel.setLayout(new GridLayout(3,3)); bbox = new JButton[9]; for (int h = 0; h < 9; h++) { panel.add(bbox[h]); bbox[h].addActionListener(this); //error 2 } Container c = getContentPane(); //error 3 c.add(panel, BorderLayout.CENTER); JFrame f = new JFrame("GUI Test!!!"); f.add(c); } } } I've commented the three lines in which the following three errors are reported by the compiler: (Toggle Plain Text) guiTest is not abstract and does not override abstract method actionPerformed(java.awt.event.ActionEvent) in java.awt.event.ActionListener public class guiTest implements ActionListener { ^ non-static variable this cannot be referenced from a static context bbox[h].addActionListener(this); ^ cannot find symbol symbol : method getContentPane() location: class TicTacToe Container c = getContentPane(); ^ guiTest is not abstract and does not override abstract method actionPerformed(java.awt.event.ActionEvent) in java.awt.event.ActionListener public class guiTest implements ActionListener { ^ non-static variable this cannot be referenced from a static context bbox[h].addActionListener(this); ^ cannot find symbol symbol : method getContentPane() location: class TicTacToe Container c = getContentPane(); ^ Any help? Thanks in advance! __________________ Children in the dark cause accidents, and accidents in the dark cause children. http://www.ronincoders.org

Mar 10th, 2007, 8:29 PM	#3
titaniumdecoy Expert Programmer Join Date: Nov 2005 Posts: 843 Rep Power: 3	No offense, but the multitude of fundamental problems with your code most likely indicates that your understanding of the Java language is insufficient to be working with GUIs. Instead of taking the time to write out an explanation for each problem, I rewrote the code for you to study. (Toggle Plain Text) import java.awt.; import java.awt.event.; import javax.swing.; public class GUITest extends JFrame implements ActionListener { private static JButton[] bbox; public GUITest() { super("GUI Test"); setLayout(new GridLayout(3,3)); bbox = new JButton[9]; for (int i = 0; i < bbox.length; i++) { bbox[i] = new JButton(Integer.toString(i)); bbox[i].addActionListener(this); add(bbox[i]); } pack(); setVisible(true); } public static void main(String args[]) { new GUITest(); } public void actionPerformed(ActionEvent evt) { // This method is called when a button is clicked } } import java.awt.; import java.awt.event.; import javax.swing.; public class GUITest extends JFrame implements ActionListener { private static JButton[] bbox; public GUITest() { super("GUI Test"); setLayout(new GridLayout(3,3)); bbox = new JButton[9]; for (int i = 0; i < bbox.length; i++) { bbox[i] = new JButton(Integer.toString(i)); bbox[i].addActionListener(this); add(bbox[i]); } pack(); setVisible(true); } public static void main(String args[]) { new GUITest(); } public void actionPerformed(ActionEvent evt) { // This method is called when a button is clicked } } Last edited by titaniumdecoy; Mar 10th, 2007 at 8:48 PM.

Mar 10th, 2007, 10:36 PM	#4
Intimidat0r Hobbyist Programmer Join Date: May 2005 Location: Don't know, but the padded walls are a nice touch. Posts: 126 Rep Power: 0	Thanks. I am pretty new to Java. Let me ask you one more thing? Is there a way (presumably in actionPerformed()) to tell which button of the array was clicked? Or do I have to use a different method for each one? __________________ Children in the dark cause accidents, and accidents in the dark cause children. http://www.ronincoders.org

Mar 10th, 2007, 10:42 PM	#5
titaniumdecoy Expert Programmer Join Date: Nov 2005 Posts: 843 Rep Power: 3	I prefer to use the getSource() method of the ActionEvent object: (Toggle Plain Text) public void actionPerformed(ActionEvent evt) { if (evt.getSource() == bbox[0]) { // bbox[0] was pressed } } public void actionPerformed(ActionEvent evt) { if (evt.getSource() == bbox[0]) { // bbox[0] was pressed } } You can get the name of the button with the getActionCommand() method, but remember that if you change the button's text, that change will be reflected in the value returned by this function. (Toggle Plain Text) public void actionPerformed(ActionEvent evt) { if (evt.getActionCommand().equals("0")) { // The button labeled "0" was pressed } } public void actionPerformed(ActionEvent evt) { if (evt.getActionCommand().equals("0")) { // The button labeled "0" was pressed } }

Mar 10th, 2007, 10:48 PM	#6
Intimidat0r Hobbyist Programmer Join Date: May 2005 Location: Don't know, but the padded walls are a nice touch. Posts: 126 Rep Power: 0	Alright, thanks man. __________________ Children in the dark cause accidents, and accidents in the dark cause children. http://www.ronincoders.org

Mar 10th, 2007, 7:27 PM	#2
Arevos Programming Guru Join Date: Aug 2005 Location: England Posts: 1,499 Rep Power: 5	Why are you inheriting from ActionListener?

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Programming Forums > Application Development > Java

Having difficulty with Swing.