QThread:在线程仍在运行时被销毁？

Question

QThread当我按下按钮Run时,我想启动我.但编译器输出以下错误:

QThread: Destroyed while thread is still running
ASSERT failure in QThread::setTerminationEnabled(): "Current thread was not started with QThread.", file thread\qthread_win.cp.

我不知道我的代码有什么问题.

任何帮助,将不胜感激.

这是我的代码:

SamplingThread::SamplingThread( QObject *parent):
   QwtSamplingThread( parent ),
   d_frequency( 5.0 )
{
   init();
}

MainWindow::MainWindow( QWidget *parent ):
QMainWindow( parent )
{.......
  .....
   run= new QPushButton ("Run",this);
   stop= new QPushButton("Stop",this);
   connect(run, SIGNAL(clicked()),this, SLOT (start()));
}

MainWindow::start
{
   SamplingThread samplingThread;
   samplingThread.setFrequency( frequency() );
   samplingThread.start();
}

int main( int argc, char **argv )
{
   QApplication app( argc, argv );
   MainWindow window;
   window.resize( 700, 400 );
   window.show();
   bool ok = app.exec();
   return ok;
}

Answer 1

正如错误消息所述:QThread: Destroyed while thread is still running.您正在方法SamplingThread内创建对象,MainWindow::start但是当该方法终止时,它会超出范围(即被销毁).我看到了两种简单的方法:

1. 您使自己成为自己SamplingThread的成员,MainWindow因此其生命周期与MainWindow实例相同

2. 您使用指针,即您创建SamplingThread使用

   SamplingThread *samplingThread = new SamplingThread;

这有帮助吗？

编辑:为了说明这两种情况,一个非常粗略的例子来说明这两种情况

#include <iostream>
#include <QApplication>
#include <QThread>

class Dummy
{
public:
  Dummy();
  void start();
private:
  QThread a;
};

Dummy::Dummy() :
  a()
{
}


void Dummy::start()
{
  a.start();
  QThread *b = new QThread;
  b->start();

  if( a.isRunning() ) {
    std::cout << "Thread a is running" << std::endl;
  }
  if( b->isRunning() ) {
    std::cout << "Thread b is running" << std::endl;
  }
}

int main(int argc, char** argv)
{
  QApplication app(argc,argv);
  Dummy d;
  d.start();
  return app.exec();
}

Answer 2

这是C ++的基础！您正在QThread堆栈上而不是堆上创建本地对象，因此当您离开method时，它会立即销毁MainWindow::start。

应该这样做：

MainWindow::MainWindow( QWidget *parent ):
QMainWindow( parent )
{
   ...

   samplingThread = SamplingThread(this);
   samplingThread->setFrequency( frequency() );

   run= new QPushButton ("Run",this);
   stop= new QPushButton("Stop",this);
   connect(run, SIGNAL(clicked()), samplingThread, SLOT(start()));
}

MainWindow::~MainWindow() {
   samplingThread->waitFor(5000);
}