Re: InvokeLater does not update in time

From:

Ian Wilson <scobloke2@infotop.co.uk>

Newsgroups:

comp.lang.java.help

Date:

Mon, 09 Oct 2006 17:52:26 +0100

Message-ID:

<oMidnb6AKObT47fYRVnyiQ@bt.com>

Ikke wrote:

Hi everybody,

I'm working on a small application that scans a lot of files for
information.

To let the user know what is going on, I update the following components:
- a JList containing log messages
- a JProgressBar indicating the progress in the current file
- a JProgressBar indicating global progress

The scan progress is a separate thread. I noticed that the JList was not
getting updated correctly, and after some Googling I found out that this
was because I was not updating it in the Event Dispatching Thread. So I
added the following piece of code:

--- code ---
    if (SwingUtilities.isEventDispatchThread())
    {
        sv.showMessage(message);
    }
    else
    {
        Runnable run = new Runnable()
        {
            public void run()
            {
                sv.showMessage(message);
            }
        };
        SwingUtilities.invokeLater(run);
    }
--- /code ---

"sv" is the JFrame containing the JList. This would ensure that a) the
JList would get updated, and b) that the results would be displayed in
the EDT.

So far so good - but as a result of the amount of files, there will be
thousands and thousands of Runnables, each waiting their turn to get
executed.

The end result is a display in which both JProgressBars are both at 100%,
and the JList still is updating a list of what's going on.

How can I let the update process for the JList keep pace with the
JProgressBars?

Even if your program can process 1000 files a second, it's not sensible
to expect a human to read 1000 filenames a second, so I'd not show the
human 1000 filenames a second.

I'd surround that block with some code to keep track of the time that
you last invoked showMessage and skip the block unless 500ms has elapsed.

An equivalent might be to put the name of the current file in a suitable
variable (every iteration) and have a scheduled repeating Timer task to
feed the current value from that to showMessage every 500ms.

Some filenames will get skipped from the user feedback but the end user
is not going to notice anyway if they are flashing past too quickly to read.