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• Difference between Delegate.BeginInvoke and Thread.Start

  - by Griever

  Existing related questions here talk about differences between: Delegate.BeginInvoke and Control.BeginInvoke Control.BeginInvoke and Thread.Start But what are the differences between Delegate.BeginInvoke and Thread.Start?

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• Stopping function on event in vb.net

  - by afilatun

  I have a vb.net application which does some processing. This processing can take a while. The application doesn't respond until the processing has ended and then it handle all events (such as click on buttons) that the user has done during the processing. I'd like to add a "Stop" button so that the user can stop the processing at some point. How can I do that? Could threading the processing (which is done in a function of the application) be a possible solution? I tried to add a button which change a boolean value and putting the code of the processing function inside a while statement based on that boolean value. However it doesn't work because the click event on the button is processed only after the end of the processing.

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• C# Step by Step Execution

  - by Sheldon

  Hi. I'm building an app that uses and scanner API and a image to other format converter. I have a method (actually a click event) that do this: private void ButtonScan&Parse_Click(object sender, EventArgs e) { short scan_result = scanner_api.Scan(); if (scan_result == 1) parse_api.Parse(); // This will check for a saved image the scanner_api stores on disk, and then convert it. } The problem is that the if condition (scan_result == 1) is evaluated inmediatly, so it just don't work. How can I force the CLR to wait until the API return the convenient result. NOTE Just by doing something like: private void ButtonScan&Parse_Click(object sender, EventArgs e) { short scan_result = scanner_api.Scan(); MessageBox.Show("Result = " + scan_result); if (scan_result == 1) parse_api.Parse(); // This will check for a saved image the scanner_api stores on disk, and then convert it. } It works and display the results. Is there a way to do this, how? Thank you very much!

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• In .NET, what thread will Events be handled in?

  - by Ben

  I have attempted to implement a producer/consumer pattern in c#. I have a consumer thread that monitors a shared queue, and a producer thread that places items onto the shared queue. The producer thread is subscribed to receive data...that is, it has an event handler, and just sits around and waits for an OnData event to fire (the data is being sent from a 3rd party api). When it gets the data, it sticks it on the queue so the consumer can handle it. When the OnData event does fire in the producer, I had expected it to be handled by my producer thread. But that doesn't seem to be what is happening. The OnData event seems as if it's being handled on a new thread instead! Is this how .net always works...events are handled on their own thread? Can I control what thread will handle events when they're raised? What if hundreds of events are raised near-simultaneously...would each have its own thread?

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• Stopping looping thread in Java

  - by halfwarp

  I'm using a thread that is continuously reading from a queue. Something like: public void run() { Object obj; while(true) { synchronized(objectsQueue) { if(objectesQueue.isEmpty()) { try { objectesQueue.wait(); } catch (InterruptedException e) { e.printStackTrace(); } obj = objectesQueue.poll(); } } // Do something with the Object obj } } What is the best way to stop this thread? I see two options: 1 - Since Thread.stop() is deprecated, I can implement a stopThisThread() method that uses a n atomic check-condition variable. 2 - Send a Death Event object or something like that to the queue. When the thread fetches a death event it exists. I prefer the 1st way, however, I don't know when to call the stopThisThread() method, as something might be on it's way to the queue and the stop signal can arrive first (not desirable). Any suggestions?

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• Unmanaged Process in Mono

  - by Residuum

  I want to start a quite expensive process (jackd) from a Mono application, and do not need full access to the process from the application itself. As the process is so expensive in terms of CPU usage, a Glib.IdleHandler for polling the process will not work, as it is never executed, and the GUI becomes unresponsive. Is there any way to have the cake and eating it at the same time in Mono? EDIT: I only need to be able to start and stop the process from Mono, I do not need information about the state of the process or if it has exited, as my application will register itself as a client to jackd, basically I need a "replacement" for bash's jackd &>/dev/null 2>&1 & for the System.Diagnostics.Process ;). Here is what I have so far for starting and stopping the process: public void StartJackd() { _jackd = new Process (); _jackd.StartInfo = _jackdStartup; if (_jackd.Start ()) { _jackd.EnableRaisingEvents = true; _jackd.Exited += JackdExited; } } public void StopJackd() { if (_jackd != null && !_jackd.HasExited) { _jackd.CloseMainWindow (); } } And somewhere else I have this code for registering the IdleHandler: GLib.Idle.Add(new GLib.IdleHandler(UpdateJackdConnections)); This handler will fire all the time, while the process is not running, but never, when jackd is running.

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• Multi-threaded downloader in C# question

  - by blez

  Currently I have multi-threaded downloader class that uses HttpWebRequest/Response. All works fine, it's super fast, BUT.. the problem is that the data needs to be streamed while it's downloading to another app. That means that it must be streamed in the right order, the first chunk first, and then the next in the queue. Currently my downloader class is sync and Download() returns byte[]. In my async multi-threaded class I make for example, list with 4 empty elements (for slots) and I pass each index of the slot to each thread using the Download() function. That simulates synchronization, but that's not what I need. How should I do the queue thing, to make sure the data is streamed as soon as the first chunk start downloading.

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• Execute another program in multi-threaded program

  - by Gary

  Hi, Just wondering how if it's possible to execute another program in a thread and send information to/get information from it. Essentially the same concept as with a child process and using pipes to communicate - however I don't want to use fork. I can't seem to find whether it's possible to do this, any help would be appreciated. Thanks

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• How refresh a DrawingArea in PyGTK ?

  - by Lialon

  I have an interface created with Glade. It contains a DrawingArea and buttons. I tried to create a Thread to refresh every X time my Canva. After a few seconds, I get error messages like: "X Window Server 0.0", "Fatal Error IO 11" Here is my code : import pygtk pygtk.require("2.0") import gtk import Canvas import threading as T import time import Map gtk.gdk.threads_init() class Interface(object): class ThreadCanvas(T.Thread): """Thread to display the map""" def __init__(self, interface): T.Thread.__init__(self) self.interface = interface self.started = True self.start() def run(self): while self.started: time.sleep(2) self.interface.on_canvas_expose_event() def stop(self): self.started = False def __init__(self): self.interface = gtk.Builder() self.interface.add_from_file("interface.glade") #Map self.map = Map.Map(2,2) #Canva self.canvas = Canvas.MyCanvas(self.interface.get_object("canvas"),self.game) self.interface.connect_signals(self) #Thread Canvas self.render = self.ThreadCanvas(self) def on_btnChange_clicked(self, widget): #Change map self.map.change() def on_interface_destroy(self, widget): self.render.stop() self.render.join() self.render._Thread__stop() gtk.main_quit() def on_canvas_expose_event(self): st = time.time() self.canvas.update(self.map) et = time.time() print "Canvas refresh in : %f times" %(et-st) def main(self): gtk.main() How can i fix these errors ?

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• Running processes at different times stops events from working - C

  - by Jamie Keeling

  Hello, This is a question which follows on from my previously answered question here At first I assumed I had a problem with the way I was creating my events due to the handles for OpenEvent returning NULL, I have managed to find the real cause however I am not sure how to go about it. Basically I use Visual Studio to launch both Process A and B at the same time, in the past my OpenEvent handle wouldn't work due to Process A looking for the address of the event a fraction of a second before Process B had time to make it. My solution was to simply allow Process B to run before Process A, fixing the error. The problem I have now is that Process B now reads events from Process A and as you expect it too returns a null handle when trying to open the events from Process A. I am creating the events in WM_CREATE message of both processes, furthermore I also create a thread at the same time to open/read/act upon the events. It seems if I run them at the same time they don't get chance to see each other, alternatively if I run one before the other one of them misses out and can't open a Handle. Can anyone suggest a solution? Thanks.

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• Is there any cross-platform threading library in C/C++?

  - by NumberFour

  Hello, I'm looking for some easy to use cross-platform threading library written in C/C++. What's your opinion on boost::thread or Pthreads? Does Pthreads run only on POSIX compliant systems? What about the threading support in the Qt library? Thanks for any hints.

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• Catch unhandled exception of invisible thread

  - by user346804

  In my C++ application i use an activeX component that runs its own thread (or several I don't know). Sometimes this components throws exceptions. I would like to catch these exceptions and do recovery instead of my entire application crashing. But since I don't have access to its source code or thread I am unsure how it would be done. The only solution I can think of is to run it in its own process. Using something like CreateProcess and then CreateRemoteThread, unsure how it could be implemented. Any suggestion on how to go about solving this?

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• Servlet doesnt appear to execute in a threaded manner

  - by RenegadeAndy

  I have developed a simple server using Tomcat which runs a servlet. The servlet calls a command line program - which takes about 20 seconds to execute then returns the result to the user via JSON. The problem is - if i make above 2 simultaneous requests, the servlet blocks until one of the previous requests is completed. An example of this can be seen below - "Im in" is the top of the servlet, and the list of results is after the servlet is executed. All requests were made at the same time - but you can clearly see they are not dealt with simultaneously. What setting do I need to change in tomcat in order to have all requests handeled at the same time? Thanks Andy Im in Im in FVFNT01 STOP_IDLE FVFNT03 STOP_IDLE FVFNT16 STOP_IDLE FVFNT17 STOP_IDLE FVFNT01 STOP_IDLE FVFNT03 STOP_IDLE FVFNT16 STOP_IDLE FVFNT17 STOP_IDLE Im in FVFNT01 STOP_IDLE FVFNT03 STOP_IDLE FVFNT16 STOP_IDLE FVFNT17 STOP_IDLE Im in FVFNT01 STOP_IDLE FVFNT03 STOP_IDLE FVFNT16 STOP_IDLE FVFNT17 STOP_IDLE Im in FVFNT01 STOP_IDLE FVFNT03 STOP_IDLE FVFNT16 STOP_IDLE FVFNT17 STOP_IDLE Im in FVFNT01 STOP_IDLE FVFNT03 STOP_IDLE FVFNT16 STOP_IDLE FVFNT17 STOP_IDLE Im in FVFNT01 STOP_IDLE FVFNT03 STOP_IDLE FVFNT16 STOP_IDLE FVFNT17 STOP_IDLE Im in FVFNT01 STOP_IDLE FVFNT03 STOP_IDLE FVFNT16 STOP_IDLE FVFNT17 STOP_IDLE

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• Unit Testing an Event Firing From a Thread

  - by Dougc

  I'm having a problem unit testing a class which fires events when a thread starts and finishes. A cut down version of the offending source is as follows: public class ThreadRunner { private bool keepRunning; public event EventHandler Started; public event EventHandler Finished; public void StartThreadTest() { this.keepRunning = true; var thread = new Thread(new ThreadStart(this.LongRunningMethod)); thread.Start(); } public void FinishThreadTest() { this.keepRunning = false; } protected void OnStarted() { if (this.Started != null) this.Started(this, new EventArgs()); } protected void OnFinished() { if (this.Finished != null) this.Finished(this, new EventArgs()); } private void LongRunningMethod() { this.OnStarted(); while (this.keepRunning) Thread.Sleep(100); this.OnFinished(); } } I then have a test to check that the Finished event fires after the LongRunningMethod has finished as follows: [TestClass] public class ThreadRunnerTests { [TestMethod] public void CheckFinishedEventFiresTest() { var threadTest = new ThreadRunner(); bool finished = false; object locker = new object(); threadTest.Finished += delegate(object sender, EventArgs e) { lock (locker) { finished = true; Monitor.Pulse(locker); } }; threadTest.StartThreadTest(); threadTest.FinishThreadTest(); lock (locker) { Monitor.Wait(locker, 1000); Assert.IsTrue(finished); } } } So the idea here being that the test will block for a maximum of one second - or until the Finish event is fired - before checking whether the finished flag is set. Clearly I've done something wrong as sometimes the test will pass, sometimes it won't. Debugging seems very difficult as well as the breakpoints I'd expect to be hit (the OnFinished method, for example) don't always seem to be. I'm assuming this is just my misunderstanding of the way threading works, so hopefully someone can enlighten me.

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• Question on a tutorial

  - by hansa

  Hello, i´m trying to get following tutorial to run and understand: http://www.ibm.com/developerworks/web/library/wa-cometjava/index.html In the example code which can be downloaded at the bottom of the page is everything in one class with two inner classes. How can i make the the thread of "MessageSender" (Listing 3) visible to "The Weatherman" (Listing 4) so i can use it in the run method without using inner classes? Thank you hansa Reformulation of Question: How to make the send-method of inner class MessageSender make accessible in ClassThatDoSomething. Example-Code: public class Example extends HttpServlet implements CometProcessor { private MessageSender messageSender = null; @Override public void init() throws ServletException { // starts thread MessageSender } public event(CometEvent) { // Object of ClassThatDoSomething gets created started } private class ClassThatDoSomething { public void start() { Runnable runnable = new Runnable() { public void run(){ messageSender.send(message); } Thread thread = new Thread(runnable); thread.start(); } } private class MessageSender implements Runnable { public void send(String message) { //... } public void run() { //...} } }

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• Do I need a semaphore for my thread in Android/Java?

  - by Henrik

  Hello all, When running a thread in Android/Java: public void run() { while (running) { if (moreTasksToExec()) { task = getNextTask() task.exec(); } } } Is it OK to let it run and not using a semaphore to block while no work needs to be executed? I am only using one thread, so I need no inter-thread synchronization.

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• discrepancy in using AsyncTask, code is executed in weird order

  - by Pentium10

  Hello, In onCreate method I hav the following order of code objItem = new DbClass(this);//the onCreate event creates the database new PrepareAdapter1().execute();//this task uses the tables, but SQLException occures, tables doesn't exists As you see in my short code, I get a new instance of the SQLiteOpenHelper class, which does create the tables in onCreate. And after that I start an AsyncTask instance where I use the created table. But I get SQLiteException as table doesn't not exists. I am using this code in wrong way? I expect the table to be created when I launch the thread.

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• Thread Question

  - by Polaris

  I have method which create background thread to make some action. In this background thread I create object. But this object while creating in runtime give me an exception : The calling thread must be STA, because many UI components require this. I know that I must use Dispatcher to make reflect something to UI. But in this case I just create an object and dont iteract with UI. This is my code: public void SomeMethod() { BackgroundWorker worker = new BackgroundWorker(); worker.DoWork += new DoWorkEventHandler(Background_Method); worker.RunWorkerAsync(); } void Background_Method(object sender, DoWorkEventArgs e) { TreeView tv = new TreeView(); } How can I create objects in background thread? I use WPF application

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• Implement a threading to prevent UI block on a bug in an async function

  - by Marcx

  I think I ran up againt a bug in an async function... Precisely the getDirectoryListingAsync() of the File class... This method is supposted to return an object containing the lists of files in a specified folder. I found that calling this method on a direcory with a lot of files (in my tests more than 20k files), after few seconds there is a block on the UI until the process is completed... I think that this method is separated in two main block: 1) get the list of files 2) create the array with the details of the files The point 1 seems to be async (for a few second the ui is responsive), then when the process pass from point 1 to point 2 the block of the UI occurs until the complete event is dispathed... Here's some (simple) code: private function checkFiles(dir:File):void { if (dir.exists) { dir.addEventListener( FileListEvent.DIRECTORY_LISTING, listaImmaginiLocale); dir.getDirectoryListingAsync(); // after this point, for the firsts seconds the UI respond well (point 1), // few seconds later (point 2) the UI is frozen } } private function listaImmaginiLocale( event:FileListEvent ):void { // from this point on the UI is responsive again... } Actually in my projects there are some function that perform an heavy cpu usage and to prevent the UI block I implemented a simple function that after some iteration will wait giving time to UI to be refreshed. private var maxIteration:int = 150000; private function sampleFunct(offset:int = 0) :void { if (offset < maxIteration) { // do something // call the recursive function using a timeout.. // if the offset in multiple by 1000 the function will wait 15 millisec, // otherwise it will be called immediately // 1000 is a random number for the pourpose of this example, but I usually change the // value based on how much heavy is the function itself... setTimeout(function():void{aaa(++offset);}, (offset%1000?15:0)); } } Using this method I got a good responsive UI without afflicting performance... I'd like to implement it into the getDirectoryListingAsync method but I don't know if it's possibile how can I do it where is the file to edit or extend.. Any suggestion???

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• logging one thread in Java using log4j

  - by Javier

  I have an web application written in Java, and I have a thread-pool. The application is huge, and I cannot make major changes, for example, I cannot change log4j. I am executing a batch process in the thread pool, and I want to log everything that goes is executed to execute that process. There will always be just one thread active in the thread pool. Any ideas of how can I do that?

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• Best ways to write a method that updates two objects in a multithreaded java environment?

  - by DanielHonig

  Suppose we have a class called AccountService that manages the state of accounts. AccountService is defined as interface AccountService{ public void debit(account); public void credit(account); public void transfer(Account account, Account account1); } Given this definition, what is the best way to implement transfer() so that you can guarantee that transfer is an atomic operation. I'm interested in answers that reference Java 1.4 code as well as answers that might use resources from java.util.concurrent in Java 5

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• Multithreaded Win32 GUI message loop

  - by Dave18

  When do you need to use this type of modified message loop in multithreaded application? DWORD nWaitCount; HANDLE hWaitArray[4]; BOOL quit; int exitCode; while (!quit) { MSG msg; int rc; rc = MsgWaitForMultipleObjects(nWaitCount, hWaitArray, FALSE, INFINITE,QS_ALLINPUT); if (rc == WAIT_OBJECT_O + nWaitCount) { while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) { if (msg.message == WM_QUIT) { quit = TRUE; exitCode = msg.wParam; break; } TranslateMessage(&msg); DispatchMessage(&msg); } } else if (rc >= WAIT_OBJECT_0 && rc < WAIT_OBJECT_0 + nwaitCount) { int nlndex = rc - WAIT_OBJECT_0; } else if (rc >= WAIT_ABANDONED_0 && rc < WAIT_ABANDONED_0+ nWaitCount) { int nlndex = rc - WAIT_ABANDONED_O; } }

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• Sync between local service with a thread and an activity

  - by Henrik

  Hello all, I'm trying to think of a way on how to sync in between a local service and the main activity. The local service has, A thread with a socket connection that could receive data at any time. A list/array with data. At any time the socket could receive data and add it to the list. The activity needs to display this data. So when the activity starts up it needs to attach or start the local service and fetch the list. It also needs to be notified if the list is updated. I think I would need to sync my list somehow so the local service does not add a new entry to it while the activity fetches the list when connecting to the service. Any ideas? Thanks.

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• [java] Threading socket handler for two sided communication in tcp port

  - by raven

  I want to make a chat which will be programed in java. one computer will host the server and the other one will initiate the socket [tcp port]. now from what I read there should be a loop that will constantly read the socket which means it will make the code stuck. I have a button that is 'actionperformed' on mouse release, I want to know if it will work along with the loops that constantly reads the socket so that it will also send the infromation I wrote. If I must thread it, I want to know if the run() method must be void because if I thread it it will mean creating a new class, and the whole GUI is one big class which includes a text area, and it's private. also how can I extract the information from the socket directly to the text area? lets say the textarea variable is called "chatOutput". thx :)

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• Thread processing in EMS connection

  - by aladine

  I am setting up a client and exchange project and both are connecting to a remote server. Exchange will connect to the server by EMS connection. While client will connect by FIX. For the aim of building of black box testing, both client and exchange engine will be given some predefined testcases to send and receive to the server. I design the client engine with multithread processing to manipulate many testcases. Actually it is able to run succesfully. For exchange engine, I wonder that multi thread is applicable in the context that the exchange engine just need to publish a message when it received msg from subscribed topic on server. Flow of messages transmission: Client--SERVER--Exchange FIX EMS Exchange--SERVER--Client EMS FIX Thanks if you can help me on this issue.

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