Re: New Swing Window Not Drawn

"Daniel Pitts" <>
22 Jan 2007 19:06:12 -0800
Hal Vaughan wrote:

Daniel Pitts wrote:

All interaction with Swing components should be done on the Event
Dispatch Thread.

Look at the class SwingUtilities
specifically the invokeLater() method

Instead of setting aFlag, you should simple fire an event on the EDT.

Even if you wanted to wait for the flag to change, you need to use
synchronization. You also shouldn't be using a busy wait (even if you
sleep for 50), but instead do something like this:

[snip my code]

Thanks -- good examples and code and points to ponder.

It would seem to me I might be able to make it a bit simpler. This class is
supposed to be a simple "Please Wait..." window that I can customize and
flash up during longer operations. I might do it with a JOptionPane, but I
also need to understand this situation anyway. I've tried using
invokeLater before and had some problems getting it to work.

Instead of having any "aFlag" or "active" or any other variable, can't I do
something like this:

[snip code]

That would provide simple methods to both open and close the window.

The CPU cycle using activities are in another class. I was trying to make
this class a simple one that I could set up in a couple lines and call
without having to create separate threads or anything like that -- in other
words, the class itself would create any needed Runnable or Threads.

The calling code would look like this (assuming this class name is

        WaitDialog wd = new WaitDialog();
        //Follow with settings for wd here

It seems to me that would still do everything the same way as what you're
talking about in the same way, just that the extra typing of creating a
Runnable() is in the WaitDialog class so all I have to do is call it with
two calls instead of creating a Runnable each time I use it.

Is that reasoning correct? If it is, I'm still having trouble getting it to
work, but I'd like to know if I understand this correctly first.


That seems like a good approach to me, the only thing I would watch out
for is to make sure your calls to "activate" and "deactivate" *don't*
occure on the EDT, otherwise your doExtensiveThings is going to block
the EDT, and your window won't show up.

Generally the way to do this is to
new Thread(new Runnable() {

Ofcourse, it might be useful to create a class "ExpensiveOperation"
abstract class ExpensiveOperation extends Thread {
   private final WaitDialog wait;
   public ExpensiveOperation(WaitDialog dialog) {
     wait = dialog;

  public void run() {
       try {
       } finally {
  protected abstract void performExpesniveOperation();

Also, if you can use Java 1.6, look into the new SwingWorker class. It
allows you a lot more interaction between the EDT and the worker thread.

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