Java Swing refresh JPanel - swing

Question

I have a Applet class (extends JApplet). Inside the class I am instantiating a JPanel and initializing a JButton whit setEnabled(true). After the user clicks this button in the Panel and does some processing, I call a method inside of the JPanel to update the panel. I then do setEnabled(false) the button clicked on the JPanel.
However, the JPanel is not "refreshing" correctly after I call add(ScrollPane) on main panel. After the processing and setting the JButton to not enabled (and I confirmed that the right data is there etc), the JPanel still is in its initialized form.
In other words, what do I need to do so that calling add(JScrollPane) on a JPanel within a applet actually refreshes the Panel?
Basically i'm wondering: if you update the panel inside a swing component which is nested inside of a JApplet, should the update be visible? What needs to be done to refresh if not?
THIS IS THE CODE:
public void actionPerformed(ActionEvent e) {
String command = e.getActionCommand();
if (STAMPA_COMMAND.equals(command)) {
stampa.setEnabled(false);
JPanel areaPrint = new JPanel();
JLabel lab = new JLabel("Wait Printing...");
areaPrint.setBackground(Color.magenta);
areaPrint.add(lab);
scrollArea.getViewport().add(areaPrint); // THIS IS THE PROBLEM...THE CHANGE ARE NOT REFRESHED
try {
PrintPdf printPDFFile;
ArrayList assegniDaStampare = new ArrayList();
for (int i = 0; i < assegni.size(); i++) {
DatiAssegno datiAss = (DatiAssegno) assegni.get(i);
if (datiAss != null && datiAss.getStatoAssegno().equals(STATUS_OK)) {
printPDFFile = new PrintPdf("Stampa Assegni", datiAss);
printPDFFile.print();
String servletLocation = "http://localhost/Servlet";
// connect to the servlet
URL studentDBservlet = new URL(servletLocation);
URLConnection servletConnection = studentDBservlet.openConnection();
servletConnection.setUseCaches(false);
servletConnection.setDefaultUseCaches(false);
servletConnection.setDoInput(true);
servletConnection.setDoOutput(true);
OutputStream outstream = servletConnection.getOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(outstream);
oos.writeObject(datiAss.idAssegno);
oos.flush();
oos.close();
ObjectInputStream inputFromServlet = new ObjectInputStream(servletConnection.getInputStream());
try {
String statusSave = (String) inputFromServlet.readObject();
} catch (ClassNotFoundException e4) {
e4.printStackTrace();
}
}
}
JPanel areaPrint2 = new JPanel();
JLabel lab2 = new JLabel("Print Complete");
areaPrint2.setBackground(Color.green);
areaPrint2.add(lab2);
scrollArea.getViewport().add(areaPrint2);
} catch (FileNotFoundException e1) {
//do something
} catch (IOException e2) {
//do something
} catch (PrinterException e3) {
//do something
}
}
if (EXIT_COMMAND.equals(command)) {
JSObject win = JSObject.getWindow(appletParent);
appletParent.stop();
appletParent.destroy();
win.eval("self.close()");
}
}

Answer 1

First off, you shouldn't be opening a connection within the action. Use a SwingWorker or some other executor to do this.
Secondly, try calling revalidate() on the panel after adding the scrollpane. These two fixes should solve the problem.