QThread完成（）信号从不发出 [英] QThread finished() signal is never emited

问题描述

所以我有一个工作类有2个插槽：StartWork（）和StopWork（），StartWork（）运行一个无限循环（它只读取和读取摄像机输入不停止）和StopWork（）方法设置bool变量为false（所以StartWork（）内的循环停止）。

根据QThread文档，现在使用它们的最好方法不是分类，但通过移动工人进入线程，所以这就是我做的。问题是，来自线程的starts（）信号被调用，但是finished（）信号从未被调用。

工作类插槽：

void StartWork（）{running = true; while（running）{do work; }}

void StopWork（）{running = false; }

QThread初始化和信号/槽连接：

  thread = new QThread（）; 
 worker = new Worker（）; 
 worker.moveToThread（thread）; 
 
 QObject :: connect（thread，SIGNAL（started（）），worker，SLOT（StartWork（）））; 
 QObject :: connect（thread，SIGNAL（finished（）），worker，SLOT（StopWork（）））; 
  

并且在我的QPushButton我这样做：

  if（pushStartStop-> text（）。toLower（）==start）
 {
 pushStartStop-> setText（Stop）; 
 thread-> start（）; 
} 
 else 
 {
 pushStartStop-> setText（Start）; 
 thread-> quit（）; 
} 
  

线程 - > start（）工作正常，StartWork调用和一切都很漂亮（GUI运行没有块等）。

但线程 - > quit（）不做任何事情，改变文本），但是它。如果我只是调用worker-> StopWork（）它的工作，但是我不能再次启动它。

我试过了thread-> exit（）但结果是一样的。我也知道子类化工作，但它看起来更丑陋，根据最近的Qt文档，子类不再是最佳。

提前感谢。 >

解决方案

您有一个永远的循环：

  void StartWork（）
 {
 running = true; 
 while（running）
 {
 do work; 
} 
} 
  

此函数将循环，因此事件循环线程在发出 started（）后被阻塞。因此， finished（）无法发出。

解决方案1： >

添加函数

  void DoWork（）
 {
 if（running）
 {
 do work 
} 
} 
  

b $ b

To Worker，并更改

  void StartWork（）
 {
 running =真正; 
} 
  

然后，只需连接 DoWork



更改函数

  void StartWork（）
 {
 running = true; 
 while（running）
 {
 do work; 
 QCoreApplication :: processEvents（）; 
} 
} 
  

使用此解决方案，您必须重新启动线程当工作程序停止其工作（ StopWork（）将强制此函数完成，因此事件循环将没有事件要处理，线程将完成）。




so i have a worker class that has 2 slots: StartWork() and StopWork(), the StartWork() one runs an infinite loop (it just reads and reads camera input non-stop) and the StopWork() method just sets a bool variable to false (so the loop inside StartWork() stops).

according to the QThread documentation, the best way to use them now is not by sub-classing but by moving workers into the thread, so that's what i do. problem is, the started() signal from the thread gets called but the finished() signal never gets called.

worker class slots:

void StartWork(){ running = true; while(running){ do work; }}

void StopWork(){ running = false; }

QThread initialization and signal/slot connection:

thread = new QThread();
worker = new Worker();
worker.moveToThread(thread);

QObject::connect(thread, SIGNAL(started()), worker, SLOT(StartWork()));
QObject::connect(thread, SIGNAL(finished()), worker, SLOT(StopWork()));

and on my QPushButton i do this:

if(pushStartStop->text().toLower() == "start")
{
    pushStartStop->setText("Stop");
    thread->start();
}
else
{
    pushStartStop->setText("Start");
    thread->quit();
}

the thread->start() works fine, and the StartWork() gets called and everything is beautiful (GUI runs with no blocks, etc).

but thread->quit() doesn't do anything, it gets called (because the button changes text) but thats it. if i just call worker->StopWork() it works, but then i can't start it again.

I've tried with thread->exit(); but the results are the same. Also i know sub-classing works, but it looks uglier and according to the recent Qt documentation, sub-classing is no longer optimal.

thanks in advance.

解决方案

You have a forever loop:

void StartWork()
{
    running = true;
    while(running)
    {
        do work;
    }
}

This function will loop, so the event loop of the thread is blocked just after having emitted started(). Thus, finished() cannot be emitted.

Solution 1:

Add the function

void DoWork()
{
    if(running)
    {
        do work
    }
}

To Worker, and change

void StartWork()
{
    running = true;
}

Then, just connect DoWork to a timer in the thread.

Solution 2:

Change the function

void StartWork()
{
    running = true;
    while(running)
    {
        do work;
        QCoreApplication::processEvents();
    }
}

With this solution, you will have to restart the thread when the worker stops its job (StopWork() will force this function to finish, so the event loop will have no events to handle and the thread will be finished).

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