在QThread中的QCoreApplication上调用quit()时出错

为了在一个单独的线程中创建一个Qt事件循环，从一个由Java编写的主应用程序调用的DLL中，我做了以下工作，基于我在这里读到的一个建议，它工作得相当好:

// Define a global namespace. We need to do this because the parameters 
// passed to QCoreApplication must have a lifetime exceeding that of the 
// QCoreApplication object
namespace ToolThreadGlobal
{
    static int argc = 1;
    static char * argv[] = { "MyVirtualMainApplication.exe", NULL };
    static QCoreApplication *coreApp = nullptr;
    static ToolThread *toolThread = nullptr;
};
//! The ToolThread class differs from a standard QThread only 
//! in its run() method
class ToolThread : public QThread
{
    //! Override QThread's run() method so that it calls 
    //! the QCoreApplication's exec() method rather than 
    //! the QThread's own
    void run() { ToolThreadGlobal::coreApp -> exec(); }
};
class ThreadStarter : public QObject
{
    Q_OBJECT
public:
    //! Constructor
    ThreadStarter()
    {
        // Set up the tool thread:
        if (!ToolThreadGlobal::toolThread)
        {
            ToolThreadGlobal::toolThread = new ToolThread();
            connect(ToolThreadGlobal::toolThread, &ToolThread::started,
                    this, &ThreadStarter::createApplication, Qt::DirectConnection);
                    // The thread's 'started' event is emitted after the thread
                    // is started but before its run() method is invoked. By 
                    // arranging for the createApplication subroutine to be 
                    // called before run(), we ensure that the required 
                    // QCoreApplication object is instantiated *within the 
                    // thread* before ToolThread's customised run() method 
                    // calls the application's exec() command.
            ToolThreadGlobal::toolThread->start();
        }
    }
    //! Destructor
    ~ThreadStarter()
    {
        // Ensure that the thread and the QCoreApplication are cleanly 
        // shut down:
        ToolThreadGlobal::coreApp -> quit();
        delete ToolThreadGlobal::coreApp;
        ToolThreadGlobal::coreApp = nullptr;
        delete ToolThreadGlobal::toolThread;
        ToolThreadGlobal::toolThread = nullptr;
    }
    //! Function to return a pointer to the actual tool thread:
    ToolThread* getThread() const { return ToolThreadGlobal::toolThread;  }
private:
    //! Create the QCoreApplication that will provide the tool 
    //! thread's event loop
    /*! This subroutine is intended to be called from the tool 
        thread itself as soon as the thread starts up.
    */
    void createApplication()
    {
        // Start the QCoreApplication event loop, so long as no 
        // other Qt event loop is already running
        if (QCoreApplication::instance() == NULL)
        {
            ToolThreadGlobal::coreApp = new QCoreApplication(ToolThreadGlobal::argc, 
                                                             ToolThreadGlobal::argv);
        }
    }
};

要使用它，从主Java应用程序线程调用的子例程只需要创建一个ThreadStarter对象它将自动创建一个ToolThread，并在其中运行QCoreApplication:

itsThreadStarter = new ThreadStarter();
itsToolThread = itsThreadStarter -> getThread();

然后我们可以用通常的方式实例化一个QObject类，将它移动到线程中，并使用QMetaObject::invokeMethod:

异步调用它的方法

itsWorker = new Worker();
itsWorker -> moveToThread(itsToolThread);
QMetaObject::invokeMethod(itsWorker, “doSomethingInteresting”);

完成后，我们只需删除ThreadStarter对象，然后一切都很好地清理了。除了烦人的消息

WARNING: QApplication was not created in the main() thread

在启动时，它似乎满足了我所有的要求。

除了……(最后，这是我的问题)。

偶尔-没有任何模式，我已经能够辨别到目前为止-我在关机过程中得到一个错误。通常出现在 行

        delete ToolThreadGlobal::coreApp;

但有时在

行

    ToolThreadGlobal::coreApp -> exec();

(当然是在线程的run()方法中执行，直到ToolThreadGlobal::coreApp -> quit()之后才返回;已完全执行)。

通常错误消息是一个简单的访问冲突;有时它是相当复杂的:

ASSERT failure in QObjectPrivate::deleteChildren(): "isDeletingChildren already set, did this function recurse?", file ..qtbasesrccorelibkernelqobject.cpp, line 1927

我认为这是因为，一旦我发出quit()命令给QCoreApplication，我应该等待一段时间，让它在删除它之前正确地关闭事件循环-就像人们通常在删除它之前调用quit()，然后在普通的QThread上等待()一样。然而，QCoreApplication似乎没有相当于wait()的命令，而且我不能实现QTimer来强制延迟，因为一旦我用quit()关闭了事件循环，它就不起作用了。因此，我不知道该怎么办。我有一个暗示，作为QCoreApplication是一个QObject，我可以调用它的deleteLater()方法，但我看不到我应该从哪里调用它。

是否有专家了解QCoreApplication和QThread的来龙去脉，并提出解决方案?还是我设计的方式有根本的缺陷?

namespace ToolThreadGlobal
{
    static int argc = 1;
    static char * argv[] = { "MyVirtualMainApplication.exe", NULL };
    static QCoreApplication *coreApp = nullptr;
    static ToolThread *toolThread = nullptr;
    static void cleanup() { coreApp->deleteLater();  coreApp = nullptr; }
};

    void createApplication()
    {
        // Start the QCoreApplication event loop, so long as no other Qt event loop
        // is already running
        if (QCoreApplication::instance() == NULL)
        {
            ToolThreadGlobal::coreApp = new QCoreApplication(ToolThreadGlobal::argc, 
                                                             ToolThreadGlobal::argv);
            connect(ToolThreadGlobal::coreApp, &QCoreApplication::aboutToQuit,
                    ToolThreadGlobal::cleanup);
        }
    }

    ~ThreadStarter()
    {
        // Ensure that the thread and the QCoreApplication are cleanly shut down:
        ToolThreadGlobal::coreApp -> quit();
        ToolThreadGlobal::toolThread -> quit();
        ToolThreadGlobal::toolThread -> wait();
        delete ToolThreadGlobal::toolThread;
        ToolThreadGlobal::toolThread = nullptr;
    }