Qt sleep main thread. just like std::thread() run.

Qt sleep main thread exec_() line. Ensure that the duration is expressed in milliseconds and is accurate for your desired delay. However, here the main reproducible reason is that the slot Multithread::check_progress is never called by ThreadWorker::finished signals, since the instance of Multithread belongs to your current thread, but the event loop is blocked. What is the proper way to close the thread gracefully on app exit? Apr 30, 2019 · The thought is that, I create the worker thread in main thread, start the worker by sending it a signal (MainWin::startWorker()), worker thread starts the work and then sends a signal with pointer to data (Worker::ImDone(Worker*)) back to main thread. Jan 13, 2025 · Consider proper thread management (e. There’s no place for sleep in the main thread of a UI application, as it blocks everything, i. It is not a task, it is not a thread pool or anything like that. even if i connect them in main thread. Dec 20, 2012 · However, before the new thread can really quit, the main thread has already finished the eventqueue, because no more events are posted to the main thread. So if you create a QObject in the app's main thread and want to use it in another thread, you need to use moveToThread() to change the affinity. Dec 8, 2016 · @squirtgun I'm not sure why the link is not what you are looking for. Dec 29, 2020 · One solution would be to initiate updates from the UI via a Timer in PerformanceMonitor instead of making the threads sleep using msleep(), but that would imply creating and starting a thread each time the timer triggers, something like: Jul 22, 2011 · As you can see I'm calling # processA() which takes no arguments thread. The GUI responds as do the slots of the worker thread class. Your post says that Qt::DirectConnection works. startpump(); sleep(1000); mypump. connect(app. OK, here is a simple example. QtCore. May 7, 2013 · Is there a wrapper function for Sleep / usleep in Qt that can be used in the main thread, or do I have to write my own wrapper? It's not a lot of code, but would be a shame to write my own if there already is one. Remember that waiting/sleeping will freeze your thread, which might reduce your program's performance. This is usually the thread that creates the QObject. Even i cant implement thread concept here as it involves many code changes. May 17, 2016 · "to use method sleep() in Qt style” - Qt-style sleep() is not to sleep() :). run function) can be different from the main Qt thread (thread that instantiates the first Qt object like a QApplication), although both "main" threads are often the same one. Simultaneous Access to Data Qt documentation states that signals and slots can be direct, queued and auto. exec(), i create an object which itself creates an object and puts it in a separate thread for running. In general, prefer to interact with objects in other threads by invoking their slots via queued connections, unless there's a pressing reason to act immediately. If you try to start a thread that is already May 14, 2022 · Here I created a simple example to show how a long-running task can block controls in our Qt Gui. To test this is true, do not modify any of your code, just add after . Jul 25, 2011 · Of course you should never call sleep() in the GUI main thread (if you don't moveToThread() your QThread then it's still in the main thread and then I would see why calling sleep should be avoided) and if you call processEvents(), do it from the GUI main thread preferably. To communicate between the main thread and the worker threads, you use signals and slots. They say something like that it is recommended to delay a call to some thread-fiddling concepts. Sep 2, 2019 · Qt Online Installer direct download: Connect that signal to a slot in the main thread, and handle the finished state there. From QThread's man page: int QThread::exec [protected] Use wait() to block the calling thread, until the other thread has finished execution (or until a specified time has passed). If the workerobject doesn't do very much, but coordinate the Feb 3, 2013 · First, I am new to Python. loop. The fact that these objects are QThreads doesn't change that. Still the thread halts at the self. just to test it works. May 4, 2016 · You cannot sleep in event based application (GUI applications are event-based). Whenever you see a sleep (especially a microsleep like you suggested) it's a good sign that your app logic could use tweaking. The handler class is running in main /UI thread and is responsible to communicate with worker class running in other thread via signal slot. From the main/UI thread I have put this worker class into new thread. Jul 21, 2020 · I am working on a project that uses a QProgressDialog during a time-consuming computation process. I tried to print the threads id's out but with no luck (after they are started ofc). processEvents , however, is usually a crutch for a poor design. I am attaching the main thread so you can observe and suggest any changes. worker-object를 QThread객체로 이동(move To Thread)하여 사용하는 방법 Jan 11, 2019 · Due to this, we think that something in the main thread hangs. Since perhaps the problem I'm facing is to do with that or at least with how it installed. Jan 27, 2013 · Important thing about Qt is that you must work with Qt GUI only from GUI thread, that is main thread. None. h 's usleep), to fully embrace Qt, but not add additional complexity to the code. Apr 20, 2018 · Be able to communicate from the main thread down to the secondary thread. just like std::thread() run. – Jul 14, 2015 · The delays that are required can be implemented without sleeping the application in a way that interrupts other functions, and without concurrent programming and without spinning the processor - the Qt application will sleep when there are no events to process. Mar 25, 2014 · Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand Feb 2, 2010 · What Georg has said is correct. Dec 25, 2019 · QThread를 이용한 스레드 생성에는 몇가지 방법이 있다. You are not stalling your GUI thread and qt events. looper. 8. A proper implementation would launch the "main code" inside a separate thread instead of the GUI. Sep 30, 2022 · Qt does not support GUI operations of any kind outside the main thread. The main object is moved to the the new thread, but holds a member pointer to an object whose thread affinity is different; the object pointed to by QThread*. start() # another way to do it, which is a bit fancier, allows you to talk back and # forth with the object in a thread safe way by communicating through signals # and slots (now that the thread is This mutex is unlocked before the thread is put to sleep and locked when the thread wakes up. The code you have is unsafe, because pause() and cancelWork() are called from outside the worker's thread, and they use no locking when modifying the worker's members. Oct 27, 2015 · It could be because of optimization, since multithread. I want it to stick around so it can process the incoming slots. But I can't do it that way cos the sleep funcs are static protected. Thank you. Because of this, you must start and stop the timer in its thread; it is not possible to start a timer from another thread. What I want is, the 2 threads get created immediatly in the main thread, and then main thread waits for them to finish. into my workflow. a public static func, would be perfect. If we add the infinite counting while loop to the main thread, the GUI freezes immediately (not responding). The application exits without waiting for quit() to take effect. Instead of stopping the thread, I can stop the thread's processing (the longRunning() method) Nov 15, 2010 · @TobySpeight yes, if it will be an expression where you sum up two number msleep(1 + 2), then the macro substitution will be usleep(1 + 2 * 1000) will be 2001 instead of 3000 Making usleep ((X) * 1000) , guarantees that (1+2) will be evaluated first. sleep(5) Terminate looper. The main thread would be processing the Qt loop, and the other threads would basically update variables and such (Positions, QPixmaps, etc. QThread also provides static, platform independent sleep functions: sleep(), msleep(), and usleep() allow full second, millisecond, and microsecond resolution respectively. I thought that this should also affect start but with multiple instances of my widget (each controlling its own thread with a worker and timer living in it) and all of that running the start works as intended - the push button Apr 16, 2016 · Hello, I develop an application with a gui and network-connection. . This is useful when you need to update a UI element from a thread. Incorrect Usage in Event Loops: Oct 10, 2015 · I know we can not put main thread in sleep, But I have tried for sleep method i did not find it & I found it in QThread only. 0. Maybe you can try to store pointer to the main thread QThread object and call QObject::moveToThread() to move your GUI objects to the main thread instead of moving QApplication into another thread. UI painting etc. You do understand that if you block the main thread, your signals to the main thread will not be processed! Sep 2, 2017 · Well initially I went for timer and shifted to thread to learn more about QT threads. I built a qt app on Linux that uses all of these and it's been running Jan 12, 2024 · I want to exec my member function in another thread. the current value of a spinbox) that can also change during the runtime of the thread. emit finishWork(); currentThread()->sleep(1000); Jun 16, 2022 · Here is the code with the example I was mentioning in the comments: class MainWindow(QMainWindow, ui_MainWindow): def __init__(self): QtWidgets. Also, since you are using more than one thread, look in the stacktraces of all threads that have your own code running. Jan 13, 2025 · Blocking the Main Thread: Solution. (Like Gdk. user input. Oct 12, 2015 · I'm using a thread to continuously perform a repeated task without blocking the main window. There is a (Unix-specific probably) work-around, doing the same as for Unix signals with Qt: use a pipe from your std::thread to the main thread. terminated signal, but that is irrelevant for the purpose of this example. terminate() After calling terminate(), we should call looper. this means emitting a signal of MyThread in the secondary thread is a race condition and slots of MyThread will be executed in the main thread, not the one it spawns. stoppump(); for instance. You always have at least one thread when you execute an application. Keep in mind lifetime of anything the callback references. LOL. The run_long_task() is simply a time. My function will emit some signals to change ui. I can understand that as we should not put main thread in sleep that may be the reason we don't have sleep for main thread. The thread needs some information from the main window (e. sleep() that will halt for 2 seconds util returning control back to the main event loop. What if I want to call sleep on the main thread? Are you going to argue that the main thread is "fundamentally asynchronous code"? – Aug 24, 2015 · All ui related code in Qt runs in the main thread. In this case As mentioned, each program has one thread when it is started. After evoking the run_long_task() method, we can no longer interact with the line edit from our UI, until the task has In multithreaded applications, you can use QTimer in any thread that has an event loop. In a thread (QThread) at some point, in the "process()" function/method, I must wait for the "encrypted()" SIGNAL belo Apr 12, 2011 · Since the QTimer is allocated in run() its should have the thread affinity of the new thread, and from what the OP shows, it looks like its affinity is to the main GUI thread, which is surprising. Jan 8, 2018 · i wanna write a basic thread example. cpp and pass them to the B class as arguments. There are some exceptions: GUI functions that only manipulate data but don't touch the window manager can be called on secondary threads, things like QImage Feb 7, 2022 · Initially, I cringed a little: One of the most important things of Qt is that the GUI needs to run in the main thread. Issue Using QThread::usleep() in the main thread can freeze the entire application. The change may be extended to the main thread, causing this function to be deprecated. This causes the current thread to sleep for secs seconds. Because of this, you must start and stop the timer in its thread; it is not possible to start a Jan 7, 2020 · Qt's GUI operations are not thread safe, so non-main threads cannot safely perform any GUI operation. Within that long-running process, you can emit whatever signals you need so the gui has sufficient information to do updates, etc. It is just a wrapper around a thread, this brings us to. I have an application which is built up by creating instances derived from QObject that I move to different threads. If you want signals to be processed by a different thread, you first need to move the worker object to that thread by using it's moveToThread method. this function can only "push" an object from the current thread to another thread, it cannot "pull" an object from any arbitrary thread to the current thread. Class B is defined by Jul 23, 2014 · I have a Thread starting from my QMainWindow that has a busy loop (execute until MainWindow ask him to close) So far I am running this loop this way : @ /// Main Loop while (antThreadRunning) {QThread::msleep(150);}@ I was wondering if a QEventLoop would be more efficient For example: @ /// Main Loop, done in . I just want to exec one function. Use wait() to block the calling thread, until the other thread has finished execution (or until a specified time has passed). running is not changed inside the loop. It is possible that your thread is blocked for something else before starting the event loops ? I have sample prepared which exactly your scenario. Jun 17, 2018 · So your worker needs to communicate with the main thread. But the sleep makes my main GUI thread non-responsive. signals/slots defined in the CameraThread class will not necessarily run in the thread's context, remember only the run() method and methods called from it are running in a separate thread. So far everything is ok. " I also searched a bit about "WARNING: QApplication was not created in the main() thread. See full list on doc. No need to sleep until the whole Jul 11, 2015 · Probably the title question is not very explicit. The Qt GUI must run in this thread. That means no widgets, QtQuick, QPixmap, or anything that touches the window manager. Avoid using it in the main thread. It also stated that if object that owns slot 'lives' in a thread different from object that owns signal, emitting such signal will be like posting message - signal emit will return instantly and slot method will be called in target thread's event loop. ui' ) Dec 3, 2024 · Usually, it is your own code and not Qt's (I've been using Qt for 20 years and this is still true for me). I want a worker thread created by the standard threading module to interact with the main UI thread, by scheduling a function on the worker thread, where that function manipulates widgets and will be run on the main UI thread. However, problems can arise due to the confusion of thread affinity. void QThread::start () This begins the execution of the thread by calling run(), which should be reimplemented in a QThread subclass to contain your code. Event based applications have main loop, that has to be running to process events, and update its state. Use move to thread will move my class to thread, which is not i want. At the end of the work of the main threads, I need to make sure that the auxiliary thread also terminated. Still basic / direct / low level threading (I’ll just call this basic) is often seen as difficult with Qt. Anyway, Qt itself doesn't provide such means, thus you could simulate it like Use wait() to block the calling thread, until the other thread has finished execution (or until a specified time has passed). It really isn’t though. 注: Qt はイベント駆動型フレームワークであるため、 wait および sleep 関数は一般に不要です。 wait () の代わりに、 finished () 信号をリッスンすることを検討してください。 Nov 28, 2018 · @Josz said in Right way to close a QThread?. For example, if your application commonly runs heavy tasks that The Qt GUI must run in this thread. Wrong, the object creation happens in the main thread. Jan 13, 2025 · The QThread::msleep () function is used to pause the execution of the current thread for a specified number of milliseconds. I built a qt app on Linux that uses all of these and it's been running Oct 1, 2013 · The main thread just handles signal that are emitted from the secondary thread to do things like update progress bars and other UI related objects - pretty academic stuff I suppose. If the worker thread is stuck, the GUI thread does not become unresponsive. Use QTimer instead for tasks that need to be executed periodically within an event loop. Nov 19, 2013 · @AliB, It's quite difficult to advise, without seeing your current code, but it sounds like the worker thread should be your main thread, assuming you've created it as an object on a different thread. 7. Does this May 18, 2014 · Your Worker objects 'live' in the main thread, that means all their signals will be handled by the main thread's event loop. Thread stack memory will be free'd, but any memory this stack pointed to won't. That's why the proper way to do this is to notify main thread from worker, and the code in main thread will actually update text box, progress bar or something else. DispatchToMainThread([] { // main thread // do UI work here }); Same code could be adapted to run code on any thread that runs Qt event loop, thus implementing a simple dispatch mechanism. [/quote]That sounds fine. All events will be executed later by QEventLoop (inside QApplication instance). This is not what I want. connect(obj. QApplication([]) app. Instead, create a separate worker thread to handle long-running tasks. When readyRead signal emits in serial port class it just added to queue of events (in global event loop). Sep 7, 2015 · You'll be much better off moving the long-running process out of the main thread so you don't need to call processEvents(). Incorrect Timing: Solution Jan 8, 2013 · When the Worker object is created, it is owned by the main threaded right ? Then so is his child Gui Object. Also, it's not thread-safe. This thread is called the "main thread" (also known as the "GUI thread" in Qt applications). Finally one quick question. Here is my slot functoin in OddCounter class. That is, before the thread has been started with start() or, in case of the main thread, before QCoreApplication has been instantiated. 2 version and uninstall the Qt 6. it takes interval as an ms. My issue now is that I have some retry logic that is happening way to quickly. May 26, 2017 · Are these merely convenience forms allowing you to specify arbitrary sleep durations in these units, or is the input argument assumed to be within a range? For example, if is use: quint sleep_msec = 6,000; QThread::msleep(sleep_msec ); Will this work without an overflow since the sleep_msec value is greater than one second? May 2, 2015 · Effective Threading Using Qt Introduction Over the years using Qt I’ve seen a lot of difficulty using threads with Qt. I just want a sleep() func - something to suspend the main thread. Jan 13, 2025 · Always create a separate thread for time-consuming tasks and use signals and slots to communicate with the main thread. On the other hand, the existence of worker threads depends on the application’s processing needs. And sleep is sometimes useful. Feb 4, 2014 · I need to run QThread::usleep() on the main thread (for various reasons). The signal in the main thread is the clicked signal that comes with a QPushButton. Consumer Class. I think only the main thread has access to the UI in Qt. The main thread automatically has an event loop when you call QApplication::exec(). g. My real question would then be : Will worker->moveToThread(thread) move also the child Gui QWidget in the new thread or will it stay in the main thread ? Jul 25, 2011 · Of course you should never call sleep() in the GUI main thread (if you don't moveToThread() your QThread then it's still in the main thread and then I would see why calling sleep should be avoided) and if you call processEvents(), do it from the GUI main thread preferably. That also eases debugging, as you have a single place the main thread will go sleeping willingly instead of being suspendend on the fly by other threads. quit() where t is an object of type MyThread, just as i have invoked t. The function f should not directly access UI elements or interact with the main thread in an unsafe manner. This is only possible as long as there is no event dispatcher installed for the thread yet. If there are new data network-connection emits a signal and gui catches it. Furthermore, the transition from the locked state to the wait state is atomic, to prevent race conditions from occurring. loadUiType( 'mainwindow. I actually have some communication routines that get stuck and the loop method is not valid :- From the thread context of a slot in my QT GUI application (upon button push), I am trying to launch a worker thread to update other another part of the GUI with the results of a CPU intensive calculation - these results will update a table or a google like map widget - so this needs to occur in the main QT application thread where it is safe May 12, 2013 · Put your UI modifications in a slot in your main window, and connect a thread signal to that slot, chances are it will work. here's the idea: i have the main event loop. I haven't been able to solve (2), but I figured out how to solve (1), which gave me a workaround to my original problem. So, pl Jan 12, 2021 · @SPlatten said in Timers cannot be ##### from another thread: @eyllanesc, mpsckClient is created in the clsMsgSender constructor which is not in a thread. Remember to include the <QThread> header to use this function. Jun 5, 2015 · I am creating an example to understand threads in Qt and want my worker thread to sleep for 1 second between each increment so I can see the debug output. Yes getData should be changed to a setter related name, will correct that. Sep 3, 2023 · I've tried to avoid needing multithreading as long as possible but now I need something that is running while not blocking the main window. – Frank Osterfeld Jan 13, 2025 · Blocking the Main Thread: Solution Always create a separate thread for time-consuming tasks and use signals and slots to communicate with the main thread. Jul 27, 2011 · Call sleep in the main thread might have som unexpected result to some users as the UI freezes and mostly it is said: don't call sleep in main thread. Aug 7, 2024 · Yeah, I'll downgrade down to the stable version (like install the Qt 6. Use Qt's thread-safe mechanisms for such communication. But, as commented by Joachim Pileborg, you should make your own QThread. – samad montazeri. processA) thread. I tryed QtConcurrent::run(). Example of valid code structure: function below will run in the process' non-main thread 'thread Dec 15, 2015 · I still suspect the event loop issue at main thread. Let's turn to the Consumer class: Jul 25, 2011 · Of course you should never call sleep() in the GUI main thread (if you don't moveToThread() your QThread then it's still in the main thread and then I would see why calling sleep should be avoided) and if you call processEvents(), do it from the GUI main thread preferably. A popular @KubaOber: A thread is not "fundamentally asynchronous". Qt uses the timer's thread affinity to determine which thread will emit the timeout() signal. : The cleanest way to do that is to design your long lasting operation so that they can be interrupted. It seems that you don't have any problems with that in general (you do see widgets in general and can interact with them?). You should instead not use threads but: remove the waitForFinished() call Apr 26, 2013 · @from PyQt4 import uic from PyQt4 import QtCore, QtGui import random from time import sleep import time from PyQt4. See threads and QObject. Please help. Aug 13, 2016 · Actually, the main thread of a process (process that executes the Process. Go down the stacktrace until you find your own code. My guess is that it has to do with calling start() in the thread constructor. Apr 1, 2016 · And now about my problem: I have noticed that the UI freezes ONLY whenever the stop() slot is triggered and the execution of the code goes through the QThread. started. This was making the GUI hung. Feel free to use any pre-existing signal that exists in the main thread, or define a new one inside a QObject that lives in the main thread. quit(), is it ever gonna execute and terminate the event loop, so it can be restarted later? Jan 15, 2015 · Sleep main thread for 5 seconds. You have several options to replace the sleeps: you can use a timer (QTimer), but it may require you to do a lot of bookkeeping between a timer event and the other. Use events or signals/slots to communicate between the main thread and the worker thread. Feb 6, 2013 · In this simple use case maybe even via a single mutex would be enough. Dec 7, 2015 · I have a simple program that consists of two threads: Main GUI thread operated by Qt QApplication::exec; TCP network thread operated by boost::asio::io_service; TCP events, such as connecting or receiving data cause changes in GUI. However, usleep is static protected. When the application starts it crashes immediately with the following error: Oct 13, 2015 · Hello Qt community, I was wondering which type of thread I should use for my project. 0-beta 2 version. finished. So there's no way to safely create a QApplication (as opposed to a QCoreApplication) and/or a UI in another thread, You should create the QAppplication first, then use a single-shot timer to queue up the other application, before calling exec(). A main thread is responsible for the GUI and creates an QThread in order to do some work with an object. e. In order to not block the main UI thread, the class that does the computation is moved to a new QThread and it is synchronized with the main thread using a start and finish signal connected using Qt::AutoConnection, the default option for QObject::connect. Dec 13, 2020 · If you going to use the sleep function you will sleep the whole program. Calling sleep_for stops that main loop, so your app doesn't process events so it doesn't react to input and doesn't repaint itself. Question: Suppose the main thread is (perhaps incorrectly) "blocked" (or busy doing some computation). If a thread was owning some resource (such as file or mutex), it won't ever release it. class Worker { void start() { Apr 4, 2022 · is the main thread supposed to call t. , waiting for completion, deletion) after thread creation. How would the "::run()" method of that worker thread look? obviously I need some kind of loop or the thread will terminate immediately. Commented Aug 2, 2016 at 17:41. Aug 24, 2015 · All ui related code in Qt runs in the main thread. Unless you're doing some very heavy synchronization (which you shouldn't anyway) worker threads have no impact on ui responsiveness. Using QThread::usleep() in the main thread can freeze the entire application. Jun 22, 2012 · I may have written something wrong above: there is no guarantee that QThread::finished() will be emitted from the main thread; it may well be emitted from the thread controlled by the QThread instance (and, looking at Qt's source, it indeed seems to be the case, at least on some platforms). IMHO, subclassing QThread in the majority of cases is not the way While you can't work with GUI objects outside of the main thread you still can interact with them through queued signal/slot connections. waitForFinished(2000)) { std::cerr << "Process running " << std::endl; } This blocks and makes using a thread useless. Would it be a solution to hold a pointer to your thread in your app, let thread signal the end of your thread, connect (to your Qt MainThread) and delete in slot. Programming Is Like Sex: One mistake and you have to support it for the rest of your life. Is this possible? Oct 11, 2012 · You can use QThread::sleep() or QThread::msleep(). sleep(5). That's something one usually doesn't want. Sleep causes main thread to sleep. 2. In such a case, Qt will post an interruption request to that thread (via requestInterruption()); will ask the thread's event loop (if any) to quit (via quit()); and will block until the thread has Apr 3, 2013 · I am using Qt in order to write a GUI application. I'm coming from a Win32/MFC/C# backgrounds, so trying all possible things in QT. In such a case, Qt will post an interruption request to that thread (via requestInterruption()); will ask the thread's event loop (if any) to quit (via quit()); and will block until the thread has Apr 6, 2018 · I need the thread for auxiliary purposes in order to remove long-term operations from the main threads. May 7, 2020 · QThread is not the thread, it's a container of the actual thread that lives on the tread that spawns it. Also remember you can call signal slot from across threads. Thus if you want GUI functionality, it must be there, and can be only signaled from other threads. Polling should be also en Aug 5, 2016 · If the thread is running some Qt event loop, you probably could. In class A, I have a private slot Refresh which is called using QTimer every two seconds and helps in updating values in QTableView. QMainWindow. QThread. SO you can keep track of no of threads that have completed their tasks/have exited. ) Sep 15, 2014 · Thanks for your answer! :) An explanation: I need this because I need to check a value of a variable using while and only goes away when the desired value is got, also I need my thread free to handle some signals during the loop execution(the condition expected by the while is got when some signal is triggered and processed) and when the desired value is got, finally the loop ends. Main thread then processes the data and update its component (say a QTreeWidget). threads_add_idle() in GTK or runOnUiThread() in Android) Apr 16, 2016 · Hello, I develop an application with a gui and network-connection. This is where the application and its GUI run. ParentThread == WorkerThread (ParentThread) Do I miss understand how the QThread works? Jul 26, 2011 · Say I wanted to have a worker thread that has slots for signals emmited from the main application thread. Looks like you sleep your main thread so QEventLoop cant execute anything while sleeping. How would that loop look like? void QThread::sleep ( unsigned long secs ) [static protected] System independent sleep. PyQt applications can have two different kinds of threads: Main thread; Worker threads; The application’s main thread always exists. I'd like to use QThread's usleep function without a wrapper (I'm currently using unistd. exec_() @ How do you properly terminate QThreads in python? Oct 14, 2021 · Actually num() func i described here internally imports multiple scripts, so in each different script based on the response an appropriate sleep time was necessary to add. Threads can be difficult and Qt provides a lot of ways to make threads easy to work with. I've tried (from the main thread): Mar 15, 2012 · self. before calling app. These functions were made public in Qt 5. If QThread::sleep() is called in the main thread, it will block the entire application's UI and responsiveness. But not Queued Connection. This method takes ownership of the object. isRunning returns True, as such the thread didn't seem to die under odd circumstances. But anyhow you managed to signal from this implementation. msecs: An integer specifying the number of milliseconds to pause the thread. – Apr 3, 2014 · I don't think that a portable solution exists (though there might be some facilities in some operation systems, like POSIX signals). exec of QEventLoop QEventLoop loop; Jun 18, 2014 · This function will not be called for objects that live outside the main thread in Qt 6. Network-connection runs in its own thread and polls continuously. at this type of delay, you can use the QTimer::singleShot function it calls only one time after your interval and not sleep the whole system. @jsulm Thank you very much, that will work in the example that I showed; But that loop was only to simplify the code. In this situation, what is the proper way to share such data between the main window and the thread? Jan 13, 2025 · QThread::sleep() は、Qt のスレッドプログラミングにおいて、指定されたミリ秒間スレッドの実行を一時停止させるための関数です。この関数を使うことで、スレッドの処理を遅延させたり、一定の間隔で処理を繰り返したりすることができます。 May 24, 2019 · Read about Qt::QueuedConnection in QObject::connect(). A secondary thread is commonly referred to as a "worker Jun 14, 2017 · Hey Guys, I am felling a little bit stupid, but I am not able to get it running on my own . Before creating main threads, I need to make sure that exist a thread that getting their's tasks. And OS will simply abruptly stop your thread at arbitrary position in the code. Applications that need that functionality should find other solutions for their event inspection needs in the meantime. The reason why I'm doing this I because the person writing "Advanced Qt Programming - Mark S" did a similar thing with QThreads that he placed in a list and checked if they where finished. Jan 13, 2025 · Always use QThread::sleep() in a separate worker thread to avoid blocking the main thread. In such a case, Qt will post an interruption request to that thread (via requestInterruption()); will ask the thread's event loop (if any) to quit (via quit()); and will block until the thread has Jul 24, 2012 · In the above code, pthread_join indeed makes main thread wait for the child threads, but the problem is, the second thread won't be created untill the first one finishes. qt. i need some way to tell the background thread that main thread has finished (to join()), so i have a bool to indicate that. The more I read about multithreading, the more I got scared of it ("a million ways to do it wrong if you don't absolutely know everything about all of it" seems a common comment). Notice the following concerning moveToThread. Feb 28, 2019 · current thread was very helpful. I built a qt app on Linux that uses all of these and it's been running Apr 6, 2018 · I need the thread for auxiliary purposes in order to remove long-term operations from the main threads. See how you call Qt and most likely there is some wrong value there. It is the simplest, and probably the May 18, 2020 · Or you might start a separate thread, which executes your function and in this function use (gasp) QThread::msleep() As I said before sleep functions are a specialized tool - here you know what you are doing. Apr 5, 2018 · I did a "release"-version but i still get "WARNING: QApplication was not created in the main() thread. A QThread::sleep() i. About the only thing I can think of to add is to further state that QObjects have an affinity with a single thread. So you can have your threads emit a signal to you upon completion. i wrongfully thought that Thread. But the slot won't exec in main thread. I am using Qt5 on Windows7. A secondary thread is commonly referred to as a "worker thread" because it is used to offload processing work from the main thread. :) The main misuse of QThreads is this: Some people subclass QThread and add slots to the subclass. Or alternativly, a QThread::currentThread()->sleep() would also do nicely. The secondary threads are often referred to as worker threads. Oct 23, 2019 · QThread::currentThread always returns the host / main thread (implausible, makes the function somewhat pointless) The QThread *thread lives inside of the Main UI Thread and thus (getting the parent thread) always returns the parent thread i. This could be useful if you don't want your Main thread to go in a blocking call wait. All widgets and several related classes, for example QPixmap, don't work in secondary threads. Aug 21, 2023 · If I'm not mistaken, even if you don't move the timer into the thread (but do move the instance of MyClass) it will work correctly. Nov 27, 2019 · The simulate function continuously generates the number without blocking any thread i. To start an event loop from a non-GUI thread, use QThread::exec(). start()? Or does t have to call quit itself, inside its event loop? this being a blocking thread with an infinite loop, if the main thread calls t. I am a long-time MatLab user (engineer, not computer scientist) and I am beginning the process of attempting to work Python, NumPy, SciPy, etc. 간단한 예제를 통해서 하나씩 알아본다. May 6, 2021 · @SGaist said in Stopping Main Gui and worker thread before completion for PyQt5:. Feb 2, 2006 · Sure, but I don't want another thread. wait() or listen for the QThread. in the main thread, your UI will block completely. Send the proper signal to stop the thread. while(!Prozess. exit) thread. 3, it is allowed to delete a QThread instance created by a call to QThread::create() even if the corresponding thread is still running. Nokia Certified Qt Specialist. Dec 23, 2009 · Long story short: don't use sleep unless you have to sleep for very short times (few hundreds milliseconds at most), otherwise the GUI will become unresponsive. In my MainWindow class I am starting a Simulator in another Thread, with the SIGNAL of the started thread I am starting a timer, who brings me data. So implies that main thread is missing the event loop. There are three main ways I’ve seen people Nov 14, 2013 · Be aware when using all kinds of sleep() etc. Problem Using QThread::msleep() in the main thread can freeze the entire application. Nov 9, 2011 · You could construct the threads in main. app = QtGui. Aug 30, 2016 · Hi, since your worker-thread comes from another API you have to use this API's methods. Since Qt 6. " on Android" and found something on the Qt Bug Dashboard. Mar 8, 2017 · It simply asks OS to kill your thread. Apr 17, 2013 · I wonder how to get back an object running in a QThread to the main thread? The following code runs in the main thread: @QThread *thread = new QThread(); MyObject *object = new MyObject(); object->moveToThread(thread); thread->start();@ I would like to get back the object instance to the main thread. This means that the thread will be temporarily inactive, allowing other threads or processes to run. But then you call start() on it. To take the advantage of threading, you need to create a secondary thread to offload the long-running operations from the main thread. That's already not thread-safe. __init__ Apr 7, 2018 · I have two classes: class A and class B. This works perfect. Hi and welcome to devnet, Thank you for the welcoming. Mar 26, 2012 · Here you moved the QProcess to another thread. io Nov 1, 2012 · Here is how I did for Sleep: If your class is derived from QThread, you can add a static public method like this: @ static void Sleep(unsigned long ms) { QThread::msleep(ms); } @ Then you can call MyThread::Sleep(1000) to sleep one second. Mar 1, 2012 · When this is printed out, I only get the main thread Id, not the threads. The timeout would then fire inside the main thread, but signal/slot connection will work across thread boundaries. The steps for using the QThread class are as follows: Therefore, when the ThreadedWorker object is moved to the new thread, this will work. Set the mutex from another thread, check it in the main threads event loop and possibly call sleep() directly. Thus I want the class to be compiled by QT but at the same time I want to mypump. Yet another reason NOT to wait! If you have to call "processEvents" then you should connect to QFutureWatcher::finished and react when it is done. via Qtconcurrent. This function was introduced in Qt 5. QThread itself is not a thread. As such the thread is stuck executing the event loop even though the event loop tells me it is not running anymore. That's why all drawing if Apr 16, 2012 · Been doing quite a bit of research but can't find the answer to this. QtCore import * ( Ui_MainWindow, QMainWindow ) = uic. Sep 20, 2010 · I have created a GUI in QT but in the mean time I am just testing the functions I have created from a main() function within the console. In these "threads" I have a QNetworkAccessManager where I do rest request to azure. That way you can raise a flag at any point in time and get them to stop more or less qu Since Qt 6. So i was trying for sleep alternative in Pyqt. Apr 8, 2024 · Hi! I wrote a small app and tried to deploy it to my Android phone running Android 12(S). lytj thfwy byg vker wlflur gdyx taib mhyj qpfc dnjd