Changing the text of a Jlabel from another method

Question

I apologize if the solution to this question is obvious, I am sure the solution is simple, I just cant seem to get it right in my head.

I have created my JFrame as shown in the code below. I am looking to change the text of a label ( lblStatus ) from within my main method and I cant seem to get it working. Do I need to create a new instance of the label or something along those lines ?

Can anyone advise me on what approach to take ?

Regards, Dan.

NB- I have removed some content to highlight the relevant code.

public class server {

private JFrame frmCorbaServer;

/**
 * Launch the application.
 */
public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                server window = new server();
                window.frmCorbaServer.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });

    // SERVER CONTENT
        // If connection made
        System.out.println("Server connected"); // I want this to display in lblStatus!


}

/**
 * Create the application.
 */
public server() {
    initialize();
}

/**
 * Initialize the contents of the frame.
 */
private void initialize() {
    frmCorbaServer = new JFrame();
    frmCorbaServer.setTitle("server 0.1");
    frmCorbaServer.setResizable(false);
    frmCorbaServer.setBounds(100, 100, 257, 153);
    frmCorbaServer.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frmCorbaServer.getContentPane().setLayout(null);

    JLabel lblStatus = new JLabel("...");
    lblServant.setFont(new Font("Tahoma", Font.PLAIN, 10));
    lblServant.setBounds(10, 36, 231, 14);
    frmCorbaServer.getContentPane().add(lblServant);
}

}

Answer 1

JLabel should be an instance member. An handler will help you modify the Label's text in instance methods.

public class server
{
   private JLabel lblStatus= new JLabel("Text") ; 

   public void changeLabel(String text) 
   {
     lblStatus.setText(text) ;
   } 

}

In main: window.changeLabel("In main") ;

This has to be done because in your initialize method, there reference to lblStatus is lost

private void initialize() {
    frmCorbaServer = new JFrame();
    frmCorbaServer.setTitle("server 0.1");
    frmCorbaServer.setResizable(false);
    frmCorbaServer.setBounds(100, 100, 257, 153);
    frmCorbaServer.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frmCorbaServer.getContentPane().setLayout(null);

    JLabel lblStatus = new JLabel("..."); // Forgotten when method finishes
    lblServant.setFont(new Font("Tahoma", Font.PLAIN, 10));
    lblServant.setBounds(10, 36, 231, 14);
    frmCorbaServer.getContentPane().add(lblServant);
}

Answer 2

I'm not familiar with CORBA programming, so I can only answer with some general advice. First you need to know when the server connects. Most likely this doesn't occur in your main() method. Is there a listener or some other callback method which is called to notify you that the server is connected?

Once you figure out that part, changing the text of a JLabel is fairly easy. First you need to declare an instance variable:

private JLabel lblStatus;

When you create the JLabel in initialize(), you don't need the declaration:

lblStatus = new JLabel("...");

Finally, when you know that the server has connected, simply call the setText() method:

lblStatus.setText("Server connected");