[英]QThread: Destroyed while thread is still running?
I would like to start my QThread
when I push on button Run . 当我按下按钮Run时,我想启动我的
QThread
。 But the compiler outputs following error: 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.
I don't know what is wrong with my code. 我不知道我的代码有什么问题。
Any help would be appreciated. 任何帮助,将不胜感激。
Here is my code: 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;
}
As the error message states: QThread: Destroyed while thread is still running
. 正如错误消息所述:
QThread: Destroyed while thread is still running
。 You are creating your SamplingThread
object inside the MainWindow::start
method but it goes out of scope (ie is destroyed) when that method terminates. 您正在
MainWindow::start
方法中创建SamplingThread
对象,但是当该方法终止时,它会超出范围(即被销毁)。 There are two easy ways that I see: 我看到了两种简单的方法:
SamplingThread
a member of your MainWindow
so its lifetime is the same as for the MainWindow
instance SamplingThread
成为MainWindow
的成员,因此其生命周期与MainWindow
实例的生命周期相同 You use a pointer, ie you create the SamplingThread
using 您使用指针,即使用创建
SamplingThread
SamplingThread *samplingThread = new SamplingThread;
Does this help? 这有帮助吗?
Edit: to illustrate the two cases, a very crude example to show the two cases 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();
}
This is basics of C++! 这是C ++的基础知识! You are creating local object of
QThread
on stack not on heap, so it gets destroys immediately when you leave method MainWindow::start
. 您正在堆栈上创建
QThread
本地对象而不是在堆上,因此当您离开方法MainWindow::start
时它会立即销毁。
It should be done like that: 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);
}
There are two different "threads" involved: One is the actual thread, the other is the C++ object representing it (and to be correct, there is another thread from which this code is started in the first place). 涉及两个不同的“线程”:一个是实际线程,另一个是表示它的C ++对象(并且是正确的,还有另一个线程,首先从该线程启动此代码)。
The error just says that the thread is still running at the point where the C++ object representing it is destroyed. 该错误只表示该线程仍然在代表它的C ++对象被销毁的位置运行。 In your code, the reason is that the QThread instance is local to
start()
. 在您的代码中,原因是QThread实例是
start()
本地实例。 Maybe you want to store the QThread in a member. 也许你想将QThread存储在一个成员中。
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