Java: setText on a JLabel in Swing issues

I have an issue setting a JLabel's text using a method in the class creating the GUI from a different class calling that method. The method to set the JLabel is called outside the GUI but when called from inside the GUI class it works. I have tested the getText() method on the label after it is called from outside the GUI class and it shows that the label has been updated. I get that it is probably a paint issue or update issue with Swing but I'm at a loss of what to do. I have tried repaint() and revalidate() on the label and then panel that it is within. Here is my current code:

public void setStatusLabel(String statusEntered) {
    //Shows the variable statusEntered has been received 
    System.out.println(statusEntered);

    //Not working
    status_label.setText(statusEntered);

    //Used this to check if the label receives the data. It does.
    String status = status_label.getText();
    System.out.println(status);
}

And the context in which I am calling it. Setups a database connection

//GUI Class reference
MainWindow mainwindow = new MainWindow();

public void connect(){
    Connection conn = null;
    try {
        String userName = "root";
        String password = "";
        String url = "jdbc:mysql://localhost:3306";
        Class.forName("com.mysql.jdbc.Driver").newInstance();
  开发者_JS百科      conn = DriverManager.getConnection(url, userName, password);

        //This works
        System.out.println("Connection Established");
        //The issue is with this guy
        mainwindow.setStatusLabel("Connection");
    }
    catch(Exception e) {
        System.err.println("Failed to connect to database");
        mainwindow.setStatusLabel("No connection");
    }
}

Any help with this would be awesome or if you have some links to suggestions, that would be awesome too! Thanks for the help.

Here is my main:

public static void main(String[] args) {
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new MainWindow().setVisible(true);
        }
    });
}

---

Your problem is possibly one of reference -- your mainwindow variable in your GUI class may not be referring to the MainWindow object that is being displayed. Do you call new MainWindow(); anywhere else in your code? If so, then you'd best pass a reference to the visualized MainWindow into this class above so that you can call methods on it that will result in something that can be seen.

For e.g.,

public class DatabaseConnection {
   // MainWindow mainwindow = new MainWindow();  *** don't do this ***
   MainWindow mainwindow;

   public DatabaseConnection(MainWindow mainwindow) {
      this.mainwindow = mainwindow; // pass in the reference in the constructor
   }

   public void connect() {
      Connection conn = null;

      // ... etc

      // now we can call methods on the actual visualized object
      mainwindow.setStatusLabel("Connection");
   }

---

what i have tried to do is that, you return the status of connection and print it on the mainWindow status_jlable, here you don't need to pass the reference of main window in the database class your just returning the status of connection and thats all you need.

public class MainWindows extends JFrame {

    private JLabel status_label;
    public MainWindows(){
        status_label  = new JLabel("Status");
    }

    public void setStatusLabel(String staus){
        status_label.setText(staus);    
    }
    /*.
     * 
     * your code for visualizing 
    .
    .
    .
    .
    .
    .*/

    public static void main(String args[]){
        MainWindows mw = new MainWindows();

        //this will return true if the connection will estblished and will false if not
        mw.setStatusLabel("Connection established "+ new DatabaseConnection().connect());

    }

}

/////////////database class

   public class DatabaseConnection{


        public boolean connect(){
            Connection conn = null;


            // adding this new variable to get connection status;
            boolean returnStatus = false;  //default return false if connection established it will true .
            try {
                String userName = "root";
                String password = "";
                String url = "jdbc:mysql://localhost:3306";
                Class.forName("com.mysql.jdbc.Driver").newInstance();
                conn = DriverManager.getConnection(url, userName, password);

                //This works
                System.out.println("Connection Established");
                //The issue is with this guy
                returnStatus = true;  // making status true if connection is established

                return returnStatus;
            }
            catch(Exception e) {
                System.err.println("Failed to connect to database");
                return returnStatus;
            }
        }

    }