Accessing interface components from a seperate class

Question

Hi there,
I've just been given a Java project to build, that involves writing an applet to allow text based communication between pairs of people. I've always thought the best way to go about it was to divide code into functional units, i.e. put the user interface code in one class and the code that responds to user interface interactions in other classes (of the same package).
The problem is getting the other classes to access the interface components created in the interface class.
So for brevity, here is my interface Applet class;
package name;
import statements here;
public class Communicate extends Applet {
declare all variables, strings, labels, combo boxes etc
//Construct the applet
public Communicate() {
try {
jbInit();
} catch (Exception ex) {
ex.printStackTrace();
//Initialize the applet
public void init() {
try {
jbInit();
} catch (Exception e) {
e.printStackTrace();
private void jbInit() throws Exception {
add components here
//Now the problem. In the interface there are combo boxes. When the user clicks a button it constructs a jframe that asks the user for a string. The idea is that the string be added to a combobox using add item. If I leave this code in the applet class it works fine, e.g.
public void jButton5_actionPerformed(ActionEvent actionEvent) {
JFrame f = new JFrame();
f.setSize(200, 200);
f.setLocation(200, 200);
f.setVisible(false);
//Add those boxes to the JFrame
JTextField titleField = new JTextField();
String title = "Please enter the title";
int result = JOptionPane.showOptionDialog(f,
new Object[] { message },
"New title", JOptionPane.OK_CANCEL_OPTION,
JOptionPane.QUESTION_MESSAGE,
null, null, null);
String title = titleField.getText();
jComboBox2.addItem(title);
//as jComboBox2 is decalred in the applet above, it adds the string no problem.
But what I'd like is the following, a title class on its own to make it easier to update and modify,
e.g.
public void jButton5_actionPerformed(ActionEvent actionEvent) {
try {
Title title = new Title();
catch (Exception ex) {
ex.printStackTrace();
with the Title class written as such:
package name;
import statements;
class Title {
Title() {
//Set the new title
JFrame f = new JFrame();
f.setSize(200, 200);
f.setLocation(200, 200);
f.setVisible(false);
//Add those boxes to the JFrame
JTextField titleField = new JTextField();
String title = "Please enter the title";
int result = JOptionPane.showOptionDialog(f,
new Object[] { message },
"New title", JOptionPane.OK_CANCEL_OPTION,
JOptionPane.QUESTION_MESSAGE,
null, null, null);
String title = titleField.getText();
*** Here is the problem: How do I reference jComboBox2 which is declared in the original applet class?
jComboBox2.addItem(title); (this wont work!)
public static void main(String[] args) {
Title title = new Title();
I'd thought perhaps I needed to create an instance of the applet and pass it to the second class to use it, so it can reference the components, but I'm not sure how to do this with an applet.
Thanks
Maria

Answer 1

I'm not going to look at your unformatted code, but I'll give you some general hints:
Have one set of classes being the GUI
Have one set of classes being the data (the chat history, basically)
Have one set of classes being the logic
Have one interface for the logic to manipulate the data (e.g. addNewMessage(String)
Have one interface for the GUI to get the data that's to be displayed (e.g. getLastTenMessages())
Have one interface for the logic to notify the GUI of changed data (refresh())
Have one interface for the GUI to notify the logic of user input (e.g. sendMessage(String))
The logic will receive data either from the user and send it, as well as storing it in your chat log, or it will receive it from the network and add it to the data model, both times notifying the GUI of changes afterwards.