Java

15-Aug-12 23:53

First lets give some context, I've just created a client and server but they don't work without using console So I've decided to create a GUI on top they'll communicate though the Stack, but that's all for a later date, right now I get a error on the Even listener which says that the JTextField is empty upon .getText() even though it's not. I've looked though it, but since I'm quite new to the whole Swing field, it's a challenge for me to fix the problem. It really is a simple GUI.

Java

import java.awt.Button;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Stack;

import javax.swing.*;
public class GUI extends JFrame implements ActionListener{
	Stack<String> incoming = null;
	Stack<String> outgoing = null;
	JTextField input;
	JTextArea output;
	Button button;
	public GUI(){
		
		setTitle("Satire v1.0.1");
		setSize(320,360);
		setLocationRelativeTo(null);
		setDefaultCloseOperation(EXIT_ON_CLOSE);
		
		JPanel panel = new JPanel();
		panel.setLayout(null);
		
		output = new JTextArea();
		output.setBounds(0, 0, 300, 300);
		output.setEditable(false);
		
		input = new JTextField();
		input.setBounds(0, 300, 260, 20);
		
		button = new Button("SEND");
		button.setBounds(250, 300, 50, 20);
		button.addActionListener(this);
		
		getContentPane().add(panel);
		panel.add(button);
		panel.add(input);
		panel.add(output);
	}
	public void actionPerformed(ActionEvent e) { 
		GUI gui = new GUI();
		try{
			String out = gui.input.getText();
			gui.input.selectAll();
			outgoing.add(out);
		}catch(NullPointerException e3){}
		gui.output.append(outgoing.pop());
	}
	
	public static void main(String[] args){
		 SwingUtilities.invokeLater(new Runnable() {
			 public void run(){
				 GUI cGUI = new GUI();
				 cGUI.setVisible(true);
			 }
		 });
	}
}

pasztorpisti16-Aug-12 0:28

16-Aug-12 0:28

You are new to object oriented programming as well, arent you? Smile | :)

Instead of this:

Java

public void actionPerformed(ActionEvent e) {
    GUI gui = new GUI();
    try{
        String out = gui.input.getText();
        gui.input.selectAll();
        outgoing.add(out);
    }catch(NullPointerException e3){}
    gui.output.append(outgoing.pop());
}

Use this:

Java

public void actionPerformed(ActionEvent e) {
    try{
        String out = input.getText();
        input.selectAll();
        outgoing.add(out);
    }catch(NullPointerException e3){}
    output.append(outgoing.pop());
}

Joshua Waring16-Aug-12 0:45

16-Aug-12 0:45

I have made the edit, yes I'm new, but learning fast, a lot faster than expected.
though the edit has been made, there was no change to the error. What I don't understand is that the field isn't empty D:

pasztorpisti16-Aug-12 0:55

16-Aug-12 0:55

There you go. This time I compiled/tested it, contained another big mistake. Why have you used those stacks? You should check the error messages as well in the console output!!! You program threw exceptions!

Java

import java.awt.Button;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Stack;
 
import javax.swing.*;
public class GUI extends JFrame implements ActionListener{
	JTextField input;
	JTextArea output;
	Button button;
	public GUI(){
		
		setTitle("Satire v1.0.1");
		setSize(320,360);
		setLocationRelativeTo(null);
		setDefaultCloseOperation(EXIT_ON_CLOSE);
		
		JPanel panel = new JPanel();
		panel.setLayout(null);
		
		output = new JTextArea();
		output.setBounds(0, 0, 300, 300);
		output.setEditable(false);
		
		input = new JTextField();
		input.setBounds(0, 300, 260, 20);
		
		button = new Button("SEND");
		button.setBounds(250, 300, 50, 20);
		button.addActionListener(this);
		
		getContentPane().add(panel);
		panel.add(button);
		panel.add(input);
		panel.add(output);
	}
	public void actionPerformed(ActionEvent e) { 
		try{
			String out = input.getText();
			output.append(input.getText());
			input.selectAll();
			input.requestFocusInWindow();
		}catch(NullPointerException e3){}
	}
	
	public static void main(String[] args){
		 SwingUtilities.invokeLater(new Runnable() {
			 public void run(){
				 GUI cGUI = new GUI();
				 cGUI.setVisible(true);
			 }
		 });
	}
}

Joshua Waring16-Aug-12 1:22

16-Aug-12 1:22

the purpose of the stack was for when I implements it into my chat client I'll have something to send it by, without changing the code around too much. I personally don't see how it caused an error.

pasztorpisti16-Aug-12 1:50

16-Aug-12 1:50

It caused an error because in java every object is used by reference. You had there a null reference to a stack object, actually you haven't created your stack object and when you tried to use it that was a NullPointerException! Smile | :)

Joshua Waring16-Aug-12 2:02

16-Aug-12 2:02

Meaning i should of put Stack<string> incoming = new Stack<string>();

pasztorpisti16-Aug-12 2:12

16-Aug-12 2:12

Yep. Common mistake when starting java. In java only the primitive types are self contained, everything else is just a null or uninitialized reference without initialization.

Joshua Waring16-Aug-12 3:57

16-Aug-12 3:57

Hopefully you could help me with this one, I've found the problem (Thanks to the breakpoints) My main created a thread1 and then thread1 created thread 2, both of which contain a while(true) (Then just sit and wait for input and output) but when thread1 creates thread2 it doesn't go past the line which creates thread2 which Isn't what I thought would happen... I thought Thread1 would create thread2 then proceeds to the loop for user input.

pasztorpisti16-Aug-12 4:08

16-Aug-12 4:08

You are right that should happen.

Joshua Waring16-Aug-12 4:11

16-Aug-12 4:11

I see no error but to call a implements Runnable I use the line,

Java

(new Thread(new accept(br))).start();

if that helps

pasztorpisti16-Aug-12 4:24

16-Aug-12 4:24

Not to be rude but maybe you should learn the basics first, correct threading is more or less an advanced topic. Actually the java tutorials put together by sun is exceptionally good: http://docs.oracle.com/javase/tutorial/[^]
There is a paragraph on that page with "Trails Covering the Basics" header, you should read through that carefully, you will find topics about threading in the "Essential Java Classes" part, but read it from the beginning to the end without skipping. After this basic tutorial you won't ask questions like this.

Joshua Waring16-Aug-12 2:13

16-Aug-12 2:13

Any special features and tricks to Eclipse Debugger, I've hit an error while fusing it to the client. the server gets the connection but all input is just added to the JTextArea without being sent to the server even though it's told to send. I'd prefer to fix this one so I don't have to spam these forums.

pasztorpisti16-Aug-12 1:00

16-Aug-12 1:00

Start using a good java IDE. Eclipse is one of the best free IDEs out there, choosing that you can only win. Download it and learn its basic features (how to set up a project and how to debug in it).

Advice regarding your program: Hook the input of your textbox and perform the "send text" action when the user presses enter in the textfield.

When sending the text it might be a better idea to clear the textfield instead of selecting its contents.