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  • Simple multi-threading - combining statements to two lines.

    - by Adam
    If I have: ThreadStart starter = delegate { MessageBox.Show("Test"); }; new Thread(starter).Start(); How can I combine this into one line of code? I've tried: new Thread(delegate { MessageBox.Show("Test"); }).Start(); But I get this error: The call is ambiguous between the following methods or properties: 'System.Threading.Thread.Thread(System.Threading.ThreadStart)' and 'System.Threading.Thread.Thread(System.Threading.ParameterizedThreadStart)'

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  • .NET: Best way to execute a lambda on UI thread after a delay?

    - by Scott Bussinger
    I had a situation come up that required running a lambda expression on the UI thread after a delay. I thought of several ways to do this and finally settled on this approach Task.Factory.StartNew(() => Thread.Sleep(1000)) .ContinueWith((t) => textBlock.Text="Done",TaskScheduler.FromCurrentSynchronizationContext()); But I'm wondering if there's an easier way that I missed. Any suggestions for a shorter, simpler or easier technique? Assume .NET 4 is available.

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  • How to Stop Current Playing Song When using one thread with JLayer?

    - by mcnemesis
    I recently used a solution to the one-thread-at-a-time problem whe using Jlayer to play mp3 songs in Java. But this solution by Kaleb Brasee didn't hint at how you could stop the player, i.e how could one then call player.close()? Kaleb's code was: Executor executor = Executors.newSingleThreadExecutor(); executor.execute(new Runnable() { public void run() { /* do something */ } }); and this is the code I put in run() if(player != null) player.close(); try{ player = new Player(new FileInputStream(musicD.getPath())); player.play(); }catch(Exception e){} The problem is that much as this solves the problem of keeping the gui active while the music plays (in only one other thread -- what i'd wanted), I can't start playing another song :-( What could I do?

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  • How do I create a thread-safe write-once read-many value in Java?

    - by Software Monkey
    This is a problem I encounter frequently in working with more complex systems and which I have never figured out a good way to solve. It usually involves variations on the theme of a shared object whose construction and initialization are necessarily two distinct steps. This is generally because of architectural requirements, similar to applets, so answers that suggest I consolidate construction and initialization are not useful. By way of example, let's say I have a class that is structured to fit into an application framework like so: public class MyClass { private /*ideally-final*/ SomeObject someObject; MyClass() { someObject=null; } public void startup() { someObject=new SomeObject(...arguments from environment which are not available until startup is called...); } public void shutdown() { someObject=null; // this is not necessary, I am just expressing the intended scope of someObject explicitly } } I can't make someObject final since it can't be set until startup() is invoked. But I would really like it to reflect it's write-once semantics and be able to directly access it from multiple threads, preferably avoiding synchronization. The idea being to express and enforce a degree of finalness, I conjecture that I could create a generic container, like so: public class WoRmObject<T> { private T object; WoRmObject() { object=null; } public WoRmObject set(T val) { object=val; return this; } public T get() { return object; } } and then in MyClass, above, do: private final WoRmObject<SomeObject> someObject; MyClass() { someObject=new WoRmObject<SomeObject>(); } public void startup() { someObject.set(SomeObject(...arguments from environment which are not available until startup is called...)); } Which raises some questions for me: Is there a better way, or existing Java object (would have to be available in Java 4)? Is this thread-safe provided that no other thread accesses someObject.get() until after it's set() has been called. The other threads will only invoke methods on MyClass between startup() and shutdown() - the framework guarantees this. Given the completely unsynchronized WoRmObject container, it is ever possible under either JMM to see a value of object which is neither null nor a reference to a SomeObject? In other words, does has the JMM always guaranteed that no thread can observe the memory of an object to be whatever values happened to be on the heap when the object was allocated.

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  • C# How to pause/suspend a thread then continue it?

    - by Russ K
    I am making an application in C# which uses a winform as the GUI and a separate thread which is running in the background automatically changing things. Ex: public void run() { while(true) { printMessageOnGui("Hey"); Thread.Sleep(2000); . . } } How would I make it pause anywhere in the loop, because one iteration of the loop takes around 30 seconds. So I wouldnt want to pause it after its done one loop, I want to pause it on time. Thanks!

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  • gae error:AttributeError: 'NoneType' object has no attribute 'user_is_member'

    - by zjm1126
    class Thread(db.Model): members = db.StringListProperty() def user_is_member(self, user): return str(user) in self.members and thread = Thread.get(db.Key.from_path('Thread', int(id))) is_member = thread.user_is_member(user) but the error is : Traceback (most recent call last): File "D:\Program Files\Google\google_appengine\google\appengine\ext\webapp\__init__.py", line 511, in __call__ handler.get(*groups) File "D:\Program Files\Google\google_appengine\google\appengine\ext\webapp\util.py", line 62, in check_login handler_method(self, *args) File "D:\zjm_code\forum_blog_gae\main.py", line 222, in get is_member = thread.user_is_member(user) AttributeError: 'NoneType' object has no attribute 'user_is_member' why ? thanks

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  • Why does every thread in my application use a different hibernate session?

    - by Ittai
    Hi, I have a web-application which uses hibernate and for some reason every thread (httprequest or other threads related to queueing) uses a different session. I've implemented a HibernateSessionFactory class which looks like this: public class HibernateSessionFactory { private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>(); private static Configuration configuration = new AnnotationConfiguration(); private static org.hibernate.SessionFactory sessionFactory; static { try { configuration.configure(configFile); sessionFactory = configuration.buildSessionFactory(); } catch (Exception e) {} } private HibernateSessionFactory() {} public static Session getSession() throws HibernateException { Session session = (Session) threadLocal.get(); if (session == null || !session.isOpen()) { if (sessionFactory == null) { rebuildSessionFactory();//This method basically does what the static init block does } session = (sessionFactory != null) ? sessionFactory.openSession(): null; threadLocal.set(session); } return session; } //More non relevant methods here. Now from my testing it seems that the threadLocal member is indeed initialized only once when the class is first loaded by the JVM but for some reason when different threads access the getSession() method they use different sessions. When a thread first accesses this class (Session) threadLocal.get(); will return null but as expected all other access requests will yeild the same session. I'm not sure how this can be happening as the threadLocal variable is final and the method threadLocal.set(session) is only used in the above context (which I'm 99.9% sure has to yeild a non null session as I would have encountered a NullPointerException at a different part of my app). I'm not sure this is relevant but these are the main parts of my hibernate.cfg.xml file: <hibernate-configuration> <session-factory> <property name="connection.url">someURL</property> <property name="connection.driver_class"> com.microsoft.sqlserver.jdbc.SQLServerDriver</property> <property name="dialect">org.hibernate.dialect.SQLServerDialect</property> <property name="hibernate.connection.isolation">1</property> <property name="hibernate.connection.username">User</property> <property name="hibernate.connection.password">Password</property> <property name="hibernate.connection.pool_size">10</property> <property name="show_sql">false</property> <property name="current_session_context_class">thread</property> <property name="hibernate.hbm2ddl.auto">update</property> <property name="hibernate.cache.use_second_level_cache">false</property> <property name="hibernate.cache.provider_class">org.hibernate.cache.NoCacheProvider</property> <!-- Mapping files --> I'd appreciate any help granted and of course if anyone has any questions I'd be happy to clarify. Ittai

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  • Problem with basic program using Boost Threads in c++

    - by Eternal Learner
    I have a simple program which creates and executes as thread using boost threads in c++. #include<boost/thread/thread.hpp> #include<iostream> void hello() { std::cout<<"Hello, i am a thread"<<std::endl; } int main() { boost::thread th1(&hello); th1.join(); } The compiler throws an error against the th1.join() line. It says " Multiple markers at this line - undefined reference to `boost::thread::join()' - undefined reference to `boost::thread::~thread()' "

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  • C#: Populating a UI using separate threads.

    - by Andrew
    I'm trying to make some sense out of an application Ive been handed in order to track down the source of an error. Theres a bit of code (simplified here) which creates four threads which in turn populate list views on the main form. Each method gets data from the database and retrieves graphics from a resource dll in order to directly populate an imagelist and listview. From what Ive read on here (link) updating UI elements from any thread other than the UI thread should not be done, and yet this appears to work? Thread t0 = new Thread(new ThreadStart(PopulateListView1)); t0.IsBackground = true; t0.Start(); Thread t1 = new Thread(new ThreadStart(PopulateListView2)); t1.Start(); Thread t2 = new Thread(new ThreadStart(PopulateListView3)); t2.Start(); Thread t3 = new Thread(new ThreadStart(PopulateListView4)); t3.Start(); The error itself is a System.InvalidOperationException "Image cannot be added to the ImageList." which has me wondering if the above code is linked in some way. Iis this method of populating the UI recommended and if not what are the possible complications resulting from it?

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  • Any techniques to interrupt, kill, or otherwise unwind (releasing synchronization locks) a single de

    - by gojomo
    I have a long-running process where, due to a bug, a trivial/expendable thread is deadlocked with a thread which I would like to continue, so that it can perform some final reporting that would be hard to reproduce in another way. Of course, fixing the bug for future runs is the proper ultimate resolution. Of course, any such forced interrupt/kill/stop of any thread is inherently unsafe and likely to cause other unpredictable inconsistencies. (I'm familiar with all the standard warnings and the reasons for them.) But still, since the only alternative is to kill the JVM process and go through a more lengthy procedure which would result in a less-complete final report, messy/deprecated/dangerous/risky/one-time techniques are exactly what I'd like to try. The JVM is Sun's 1.6.0_16 64-bit on Ubuntu, and the expendable thread is waiting-to-lock an object monitor. Can an OS signal directed to an exact thread create an InterruptedException in the expendable thread? Could attaching with gdb, and directly tampering with JVM data or calling JVM procedures allow a forced-release of the object monitor held by the expendable thread? Would a Thread.interrupt() from another thread generate a InterruptedException from the waiting-to-lock frame? (With some effort, I can inject an arbitrary beanshell script into the running system.) Can the deprecated Thread.stop() be sent via JMX or any other remote-injection method? Any ideas appreciated, the more 'dangerous', the better! And, if your suggestion has worked in personal experience in a similar situation, the best!

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  • Can my thread help the OS decide when to context switch it out?

    - by WilliamKF
    I am working on a threaded application on Linux in C++ which attempts to be real time, doing an action on a heartbeat, or as close to it as possible. In practice, I find the OS is swapping out my thread and causing delays of up to a tenth of a second while it is switched out, causing the heartbeat to be irregular. Is there a way my thread can hint to the OS that now is a good time to context switch it out? I could make this call right after doing a heartbeat, and thus minimize the delay due to an ill timed context switch.

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  • Thread too slow. Better way to execute code (Android AndEngine)?

    - by rphello101
    I'm developing a game where the user creates sprites with every touch. I then have a thread run to check to see if those sprites collide with any others. The problem is, if I tap too quickly, I cause a null pointer exception error. I believe it's because I'm tapping faster than my thread is running. This is the thread I have: public class grow implements Runnable{ public grow(Sprite sprite){ } @Override public void run() { float radf, rads; //fill radius/stationary radius float fx=0, fy=0, sx, sy; while(down){ if(spriteC[spriteNum].active){ spriteC[spriteNum].sprite.setScale(spriteC[spriteNum].scale += 0.001); if(spriteC[spriteNum].sprite.collidesWith(ground)||spriteC[spriteNum].sprite.collidesWith(roof)|| spriteC[spriteNum].sprite.collidesWith(left)||spriteC[spriteNum].sprite.collidesWith(right)){ down = false; spriteC[spriteNum].active=false; yourScene.unregisterTouchArea(spriteC[spriteNum].sprite); } fx = spriteC[spriteNum].sprite.getX(); fy = spriteC[spriteNum].sprite.getY(); radf=spriteC[spriteNum].sprite.getHeightScaled()/2; Log.e("F"+Float.toString(fx),Float.toString(fy)); if(spriteNum>0) for(int x=0;x<spriteNum;x++){ rads=spriteC[x].sprite.getHeightScaled()/2; sx = spriteC[x].body.getWorldCenter().x * 32; sy = spriteC[x].body.getWorldCenter().y * 32; Log.e("S"+Float.toString(sx),Float.toString(sy)); Log.e(Float.toString((float) Math.sqrt(Math.pow((fx-sx),2)+Math.pow((fy-sy),2))),Float.toString((radf+rads))); if(Math.sqrt(Math.pow((fx-sx),2)+Math.pow((fy-sy),2))<(radf+rads)){ down = false; spriteC[spriteNum].active=false; yourScene.unregisterTouchArea(spriteC[spriteNum].sprite); Log.e("Collided",Boolean.toString(down)); } } } } spriteC[spriteNum].body = PhysicsFactory.createCircleBody(mPhysicsWorld, spriteC[spriteNum].sprite, BodyType.DynamicBody, FIXTURE_DEF); mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(spriteC[spriteNum].sprite, spriteC[spriteNum].body, true, true)); } } Better solution anyone? I know there is something to do with a handler, but I don't exactly know what that is or how to use one.

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  • NSMagedObjectContext, threads and NSFechedResultsController

    - by tmpz
    Dear iphone developers, Core Data newbie speaking here. In my application I have two NSManagedObjectContext that refer to that same NSPersistentStorageController. One ManagedObjectContext (c1) is in the main thread --created when I create a NSFetchedResultsController -- and the second ManagedObjectContext (c2) created in a second thread, running in the background, detached from the main thread. In the background thread I pull some data off a website and insert the entities created for the pulled data in the thread's ManagedObjectContext (c2). In the meanwhile, the main thread sits doing nothing and displaying a UITableView whose data do be display should be provided by the NSFetchedResultsController. When the background thread has finished pulling the data and inserting entities in c2, c2 saves, and the background thread notifies the main thread that the processing has finished before it exiting. As a matter of fact, the entities that I have inserted in c2 are know by c1 because it can ask it about one particular entity with [c1 existingObjectWithID:ObjectID error:&error]; I would expect at this point, if I call on my tableview reloadData to see some rows showing up with the data I pulled from the web in the background thread thanks to the NSFetchedResults controller which should react to the modifications of its ManagedObjectContext (c1). But nothing is happening! Only if I restart the application I see what I have previously pulled from the web! Where am I doing things wrong? Thank you in advance!

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  • Wait for inline thread to complete before moving to next method...

    - by Tyler
    Hello, I have an android app where I am doing the following: private void onCreate() { final ProgressDialog dialog = ProgressDialog.show(this, "Please wait..", "Doing stuff..", true); new Thread() { public void run() { //do some serious stuff... dialog.dismiss(); } }.start(); stepTwo(); } And I would like to ensure that my thread is complete before stepTwo(); is called. How can I do this? Thanks!

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  • Implementing deadlock condition

    - by Bhaskar
    I am trying to implementing deadlock condition but somehow I am not able to get it working. Both the threads Thread1 and Thread2 are entering in the run function but only one of them enters in Sub/Sum depending on who entered run first. Example : if Thread2 entered run first the it will call sub() and Thread1 never calls sum(). I have also added sleep time so that Thread2 sleeps before calling sum() and Thread1 gets enough time to enter Sum() but Thread1 never enters. public class ExploringThreads { public static void main(String[] args) { // TODO Auto-generated method stub threadexample a1 = new threadexample(); Thread t1 = new Thread(a1, "Thread1"); Thread t2 = new Thread(a1,"Thread2"); t1.start(); t2.start(); } } class threadexample implements Runnable{ public int a = 10; public void run(){ if(Thread.currentThread().getName().equals("Thread1")) sum(); else if(Thread.currentThread().getName().equals("Thread2")) sub(); } public synchronized void sum() { try { Thread.sleep(2000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println(Thread.currentThread().getName()+"In Sum"); sub(); } public synchronized void sub() { try { Thread.sleep(2000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println(Thread.currentThread().getName()+"In Sub"); sum(); } }

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  • Is it possible to start (and stop) a thread inside a DLL?

    - by Jerry Dodge
    I'm pondering some ideas for building a DLL for some common stuff I do. One thing I'd like to check if it's possible is running a thread inside of a DLL. I'm sure I would be able to at least start it, and have it automatically free on terminate (and make it forcefully terminate its self) - that I can see wouldn't be much of a problem. But once I start it, I don't see how I can continue communicating with it (especially to stop it) mainly because each call to the DLL is unique (as far as my knowledge tells me) but I also know very little of the subject. I've seen how in some occasions, a DLL can be loaded at the beginning and released at the end when it's not needed anymore. I have 0 knowledge or experience with this method, other than just seeing something related to it, couldn't even tell you what or how, I don't remember. But is this even possible? I know about ActiveX/COM but that is not what I want - I'd like just a basic DLL that can be used across languages (specifically C#). Also, if it is possible, then how would I go about doing callbacks from the DLL to the app? For example, when I start the thread, I most probably will assign a function (which is inside the EXE) to be the handler for the events (which are triggered from the DLL). So I guess what I'm asking is - how to load a DLL for continuous work and release it when I'm done - as opposed to the simple method of calling individual functions in the DLL as needed. In the same case - I might assign variables or create objects inside the DLL. How can I assure that once I assign that variable (or create the object), how can I make sure that variable or object will still be available the next time I call the DLL? Obviously it would require a mechanism to Initialize/Finalize the DLL (I.E. create the objects inside the DLL when the DLL is loaded, and free the objects when the DLL is unloaded). EDIT: In the end, I will wrap the DLL inside of a component, so when an instance of the component is created, DLL will be loaded and a corresponding thread will be created inside the DLL, then when the component is free'd, the DLL is unloaded. Also need to make sure that if there are for example 2 of these components, that there will be 2 instances of the DLL loaded for each component. Is this in any way related to the use of an IInterface? Because I also have 0 experience with this. No need to answer it directly with sample source code - a link to a good tutorial would be great.

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  • Can I un-assign (clear) all fields of an instance?

    - by Roman
    Is there a simple way to clear all fields of an instance from a an instance? I mean, I would like to remove all values assigned to the fields of an instance. ADDED From the main thread I start a window and another thread which controls state of the window (the last thread, for example, display certain panels for a certain period of time). I have a class which contains state of the window (on which stage the user is, which buttons he already clicked). In the end, user may want to start the whole process from the beginning (it is a game). So, I decided. So, if everything is executed from the beginning, I would like to have all parameter to be clean (fresh, unassigned). ADDED The main thread, creates the new object which is executed in a new thread (and the old thread is finished). So, I cannot create a new object from the old thread. I just have a loop in the second thread.

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  • Control.Invoke() vs. Control.BeginInvoke()

    - by user590088
    First of all, I would like to apologize for my bad grammar since English is not my native tongue. This is my understanding: Control.Invoke(delegated_method) // Executes on the thread wich the control was created on witch holds its handle ,typically this would be the main thread of a winform application . Control.BeginInvoke(delegated_method // Executes asynchronously on a threadPool Thread . According to MSDN, it says Executes a delegate asynchronously on the thread that the control's underlying handle was created on. My QUESTION : Am I to understand that beginInvoke treats the main thread in this matter as it would the thread pool, and execute the delegated method on the main thread when it "gets a chance" ? Another question which is raised, is it possible to create a control not on the main thread ? if so could someone give me an example?

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  • Java Daemon Threading with JNI

    - by gwin003
    I have a Java applet that creates a new non-daemon thread like so: Thread childThread = new Thread(new MyRunnable(_this)); childThread.setDaemon(false); childThread.start(); Then my MyRunnable object calls a native method that is implemented in C++: @Override public void run() { while (true) { if (!ran) { System.out.println("isDaemon: " + Thread.currentThread().isDaemon()); _applet.invokePrintManager(_applet.fFormType, _applet.fFormName, _applet.fPrintImmediately, _applet.fDataSet); ran = true; } } } This C++ method calls into a C# DLL that shows a form. My problem is, whenever the user navigates away from the page with a Java applet on it, JVM (and my C# form) is killed. I need the form and JVM to remain open until it is closed by the user. I tried setting my thread to be a non-daemon thread, which is working because System.out.println("isDaemon: " + Thread.currentThread().isDaemon() prints isDaemon: false. Is there something related to the way that the C# form is created (is there another thread I'm not accounting for) or something I am overlooking?? My thread is not a daemon thread, but the JVM is being killed anyways.

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  • Application that provides unique keys to multiple threads

    - by poly
    Thanks all for your help before. So, this is what I came up with so far, the requirements are, application has two or more threads and each thread requires a unique session/transaction ID. is the below considered thread safe? thread 1 will register itself with get_id by sending it's pid thread 2 will do the same then thread 1 & 2 will call the function to get a unique ID function get_id(bool choice/*register thread or get id*/, pid_t pid) { static int pid[15][1]={0};//not sure if this work, anyway considor any it's been set to 0 by any other way than this static int total_threads = 0; static int i = 0; int x=0,y=0; if (choice) // thread registeration part { for(x=0;x<15;x++) { if (pid[x][0]==0); { pid[x][0] = (int) pid; pid[x][1] = (x & pidx[x][1]) << 24;//initiate counter for this PID by shifting x to the 25th bit, it could be any other bit, it's just to set a range. //so the range will be between 0x0000000 and 0x0ffffff, the second one will be 0x1000000 and 0x1ffffff, break; } total_threads++; } } //search if pid exist or not, if yes return transaction id for(x=0;x<15;x++) { if (pid[x][0]==pid); { pid[x][1]++;//put some test here to reset the number to 0 if it reaches 0x0ffffff return pid[x][1]; break; } } }

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