Future.get and the event despatch thread blocking

neeeyaaarghhhh
been tying myself in knots thinking about this
Following one of the java tech tips I've been using Callable and Future objects when I want to return a result from a task, in my case it's usually some file processing
So I have a file chooser gui, I select a file and launch my Callable and await the result in Future.get...
Now the problem is... Future.get I understand blocks the calling thread until the computation / work in the Callable is done and the result returned. In this case the blocked thread will be the event despatch thread... which causes problems as during my file reading I have a JProgressBar running and updating. Well at least I did, now it doesn't show up at all as all the updates to the JProgressBar via invokeLater are queued (as event despatch thread is blocked) until after the work thread has finished
How do I launch a Callable, await the result and have some limited gui activity as the task progresses? The only solution I've found is to have the ProgressBar in a modal dialog, to block out the rest of the gui like this whilst I do the work in the event despatch thread (and drop the idea of threading altogether)
Is my mental modal of how worker threads should spin off from the event thread flawed or am I just missing some 1 line command?

In the situation of updating the gui, you usually want to pass some sort of callback object to the asynchronous code and have that callback method run on the gui event thread.
public class GuiClass {
public void handleResult(Object data);
public void startTask() {
threadpool.execute(new Runnable() {
    public void run() {
      // ... do asynch work ...
      final Object myResult = ...;
      SwingUtilities.invokeLater(new Runnable() {
        public void run() {
          handleResult(myResult);
}In this code, the startTask method is called on the gui thread. it starts some async work on the threadpool. when finished, the asynch task queues the result to be handled back on the gui thread. the handleResult method is called later on the gui thread with the final result. thus, no blocking of the gui thread.
The Callable interface is great for when the invoking thread needs to wait for a result, but you pretty much never want to do this with the gui thread.

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Flags and the Event Thread

I was writing code for a game and I realized that the AWT event thread could change the value of a flag while I'm in the process of updating the game state. This can cause a few problems, or it could even leave events not handled because of it. I see code like this all the time as a fix to the threading issues, am I missing something or is it really a solution? I can't post the actual code as it's too long, so I created a simple example:
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}Basically I have a game loop, where I update the game state, handle events, then draw things to the screen. Each time a key is pressed or released, I set the appropriate value to isKeyDown from the AWT event thread. The desirable output is to have the booleans equal to each other so that "false false" or "true true" is printed out on the screen constantly, but once in a while I'll get a "false true" or "true false", which is expected but obviously not wanted.
So one solution is right there commented out (synchronizing), though most people seem to avoid it. I see everybody using flags like this, so I'm wondering if I'm missing some obvious solution to the problem or if it's really even that big of a deal. I don't see any other fix, but that's why you're all here. ;)
Thanks.

Swing related questions should be posted in the Swing forum.
I converted your simple example to use a Swing Timer instead of a while(true) loop with a Thread.sleep. I experienced no problems as expected since all the code will be executed in the Event Dispatch Thread (EDT).
Of course using this approach could make the game less responsive if your game logic is extensive and hogs the EDT, but given that you try to invoke your game logic every 100 millisecond I assume it can't be that extensive.
Anyway here is the code I used as a test:
import java.awt.event.*;
import javax.swing.*;
public class EventTest extends JFrame implements KeyListener, ActionListener
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          if(cache != isKeyDown)
               System.out.println("PROBLEM!");
     public static void main(String[] args)
          new EventTest();
}

..this method should be invoked from the event-dispatching thread?

I see this (the title that is) in every single Java demo/example program on this (Sun's) site. However, I just tend to
public static void main(String[] args){
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}And I've seen this approach on other sites and other example programs.
So what exactly is better about this;
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tia.

Is it just me? For some reason it rubs me the wrong way that swing isn't thread safe. From what I've read, my understanding is that its safe to modify swing components from other threads as long as they haven't asked to be painted. If you don't do paint(), pack() or setVisible(true) until the end of your initialization, you will be safe.
The reason for not being thread safe is almost certainly performance. Swing is slow enough as it is. Since the vast majority of Swing activity takes place in response to events and thus is on the EDT, there usually isn't a problem.
This is a serious nuisance in network and database programs where multiple threads are used. I end up using invokeLater a lot in those cases, but never for initialization. Sun has only started to recomment that recently.
Note that the fireXXX methods do not put the event on the EDT, these simply create Event objects and send them to Listeners. If they are executed off the EDT the Listeners will get called off the EDT.

Executing Code outside of the Event Dispatcher Thread

Hello,
I have just come to learn that any actionPerformed() method that is called after an event occurs actually runs in the Event Dispatcher. So, for example, if you click on a button, any code that is run as a result is run in the event dispatcher.
So there are two things I am wondering about. First, If i run code in response to a user event, then it doesn't have to use invokeLater() to update GUI components because it's already being run in the event thread? Second, if I run code in response to an event but it's computationally expensive and I do not want to run it in the Event Dispatcher thread, how do i do that? Will a method call cause it to do so, or do i have to specifically create a new thread for it?
My questions are a result of this: How does one normally go about updating a GUI during a long process? I figured that if I could get the process to run in any thread other than the Event Dispatcher, I could call invokeLater() within it and it would update the GUI. Am I correct in assuming so?

So there are two things I am wondering about. First, If i run code in response to a user event, then it doesn't have to use invokeLater() to update GUI components because it's already being run in the event thread?
Correct. So if your response to an action is, for example, creating a new bit of UI using data which is already in memory, you can just do it.
Second, if I run code in response to an event but it's computationally expensive and I do not want to run it in the Event Dispatcher thread, how do i do that? Will a method call cause it to do so, or do i have to specifically create a new thread for it?
You will need to create a new thread: method calls are just control flow within the same thread.
You should use an object which implements Runnable and then use "new Thread(foo).start()"
My questions are a result of this: How does one normally go about updating a GUI during a long process?
You have to hop back onto the EDT whenever an update is required. I'd suggest writing yourself a little reusable class or two to help you with this - such as a listener mechanism with an implementation which handles the thread hopping.
I figured that if I could get the process to run in any thread other than the Event Dispatcher, I could call invokeLater() within it and it would update the GUI. Am I correct in assuming so?
Yes.
Should I use inner classes? I would prefer to keep them as separate classes within the same package.
Depends on all sorts of things - sometimes anonymous or declared inner objects are the way forward, sometimes public class objects, sometimes generic helper objects and sometimes utility classes. There are all sorts of different scenarios. As I say, though, it's worth writing some utility/helper classes to reuse. Personally I don't find SwingWorker is ideal so I have my own. Note that an abstract Action implementation is a very useful one, since this is precisely where you need to be doing most of the thread hopping.

Not Running on the Event Dispatch thread, but UI still freezes

The environment: I am currently working on an application that requires some heavy lifting in response to user input on a UI. To do this I am using a version of SwingWorker that was backported from java 1.6 to java 1.5 in conjunction with a slew of custom threads.
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I'm trying to use global keys hooking but why it's never get to the events ?

I created a new class and added this:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace Capture
class Hook_Keys
globalKeyboardHook gkh = new globalKeyboardHook();
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I used a breakpoint and it does doing the constructor the public Hook_Keys() part.
But never get to the events.
I took the code from here:
Global Key Hook
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Try to add the below in your form constructor:
public Form1()
InitializeComponent();
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Future.get and the event despatch thread blocking

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