使用Qt线程的最小示例

TL；博士：

我正在寻找一个简洁的Qt线程示例，我发现的只是一个复杂的"养眼药"，它声称可以展示QThread是如何工作的，但它们太多了，无法理解。

我接受了Zen的回答，因为他向我展示了我的尝试所遗漏的确切内容，然后添加了我自己的答案，成为我想看到的例子。单击此处跳过：https://stackoverflow.com/a/34561122/3491308

我最初的问题如下：

---

似乎我一定错过了什么，但我似乎无法使它像我认为的那样工作。我的完整应用程序需要有两到三个线程，所有这些线程（几乎）一起启动并永远运行：

• GUI
  • 在启动其他两个线程处理对象之前，先从文件中加载一堆对象
• 实时处理器
  • 具有TimeCriticalPriority和周期性的QTimer"中断"，试图将PC用作比我开始使用的功能强大得多的嵌入式系统。这个项目一开始是完全嵌入的，很快就变得过于复杂，无法在那里进行管理
• USB HID驱动程序
  • 连接到项目中仍然嵌入的部分

当然，核心功能在实时处理线程中，另外两个只是调整它的工作方式。因此，在实时处理器运行时，根据用户在GUI中的操作，会创建、修改和销毁处理对象，其中一些对象中的数据也会由USB产生和消耗。

我一直在寻找如何在Qt中使用线程的例子，但我一直得到复杂的"养眼药"类型的应用程序，这些应用程序混淆了线程部分。我尽我最大的努力解释它们，并写下我自己的，但我在Qt本身中不断出现segfault，我的小"游乐场"项目说我甚至没有第二个线程：

#ifndef MAIN_H
#define MAIN_H
#include <QtWidgets>
class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    MainWindow(QWidget* parent = 0);
    ~MainWindow() {}
private:
    QObject* mythingy;
private slots:
    void deleteObject(QObject* thingy);
};
class Worker : public QObject
{
    Q_OBJECT
public:
    Worker(QObject* thingy, QObject* parent = 0);
private:
    QObject* mythingy;
signals:
    void deleteObject(QObject* thingy);
private slots:
    void doWork();
};
#endif // MAIN_H
/***************
*** main.cpp ***
***************/
#include "main.h"
#include <QApplication>
int main(int argc, char* argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

MainWindow::MainWindow(QWidget* parent)
    : QMainWindow(parent)
{
    mythingy = new QObject(this);
    QThread* thisthread = this->thread();
    QThread* mainthread = QCoreApplication::instance()->thread();
    //breakpoint here to check thisthread and mainthread
    Worker* worker = new Worker(mythingy, this);
    connect(worker, SIGNAL(deleteObject(QObject*)), this, SLOT(deleteObject(QObject*)));
}
void MainWindow::deleteObject(QObject* thingy)
{
    QThread* thisthread = this->thread();
    QThread* mainthread = QCoreApplication::instance()->thread();
    //breakpoint here to check thisthread and mainthread
    delete thingy;
}

Worker::Worker(QObject* thingy, QObject* parent)
    : QObject(parent)
{
    mythingy = thingy;
    QThread* thread = new QThread(this);
    this->moveToThread(thread);
    //use a timer to allow the constructor to exit
    QTimer* timer = new QTimer(this);
    timer->setSingleShot(true);
    timer->start(1000);
    connect(timer, SIGNAL(timeout()), this, SLOT(doWork()));
    QThread* thisthread = this->thread();
    QThread* mainthread = QCoreApplication::instance()->thread();
    //breakpoint here to check thisthread and mainthread
    thread->start();
}
void Worker::doWork()
{
    QThread* thisthread = this->thread();
    QThread* mainthread = QCoreApplication::instance()->thread();
    //breakpoint here to check thisthread and mainthread
    deleteObject(mythingy);
}

如果有人能发布一个如何正确处理QThreads的例子，考虑到我对项目的描述，并且尽可能少地混乱（如果可能的话，最好比我的更短），我会非常感激

---

编辑：

根据Zen的回答，这似乎也有效：

MainWindow::MainWindow(QWidget* parent)
    : QMainWindow(parent)
{
    mythingy = new QObject(this);
    QThread* thisthread = this->thread();
    QThread* mainthread = QCoreApplication::instance()->thread();
    Worker* worker = new Worker(mythingy, this);
}
Worker::Worker(QObject* thingy, QObject* parent)
    : QObject(0)    //no real parent, so we can move to a different thread
{
    mythingy = thingy;
    QTimer* timer = new QTimer(this);
    timer->setSingleShot(true);
    timer->start(1000);
    connect(timer, SIGNAL(timeout()), this, SLOT(doWork()));
    QThread* thread = new QThread(parent);
    this->moveToThread(thread);
    thread->start();
}
void Worker::doWork()
{
    QThread* thisthread = this->thread();
    QThread* mainthread = QCoreApplication::instance()->thread();
    delete mythingy;
}

仍然在构造函数中移动自己，现在直接删除对象，而不是告诉所有者的线程去做

有什么不对的吗？

#ifndef MAIN_H
#define MAIN_H
#include <QtWidgets>
class Worker : public QObject
{
    Q_OBJECT
public:
    Worker(QObject* thingy, QObject* parent = 0);
private:
    QObject* mythingy;
private slots:
    void doWork();
};
class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    MainWindow(QWidget* parent = 0);
    ~MainWindow();
private:
    QObject* mythingy;
    Worker* myworker;
};
#endif // MAIN_H
/***************
*** main.cpp ***
***************/
#include "main.h"
#include <QApplication>
int main(int argc, char* argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}
MainWindow::MainWindow(QWidget* parent)
    : QMainWindow(parent)
{
    mythingy = new QObject(this);
    myworker = new Worker(mythingy, this);
}
MainWindow::~MainWindow()
{
    delete myworker;
}
Worker::Worker(QObject* thingy, QObject* parent)
    : QObject(0)    //no real parent, so we can move to a different thread
{
    mythingy = thingy;
    //move myself to a new thread and start it
    QThread* thread = new QThread(parent);
    connect(thread, SIGNAL(started()), this, SLOT(doWork()));
    this->moveToThread(thread);
    thread->start();
}
void Worker::doWork()
{
    //deleting an object from a different thread:
    //requires careful planning to make it safe, but seems to work as expected
    delete mythingy;
}

QThread* thisthread = this->thread();
QThread* mainthread = QCoreApplication::instance()->thread();

MainWindow::MainWindow(QWidget* parent)
    : QMainWindow(parent)
{
    mythingy = new QObject(this);
    QThread* thisthread = this->thread();
    QThread* mainthread = QCoreApplication::instance()->thread();
    //breakpoint here to check thisthread and mainthread
    //*****************
    Worker* worker = new Worker(mythingy);
    QThread* thread = new QThread();
    worker->moveToThread(thread);
    thread->start();
    //*****************
    connect(worker, SIGNAL(deleteObject(QObject*)), this, SLOT(deleteObject(QObject*)));
}
Worker::Worker(QObject* thingy, QObject* parent)
    : QObject(parent)
{
    mythingy = thingy;
//    QThread* thread = new QThread(this);
//    this->moveToThread(thread);
    //use a timer to allow the constructor to exit
    QTimer* timer = new QTimer(this);
    timer->setSingleShot(true);
    timer->start(1000);
    connect(timer, SIGNAL(timeout()), this, SLOT(doWork()));
//    QThread* thisthread = this->thread();
//    QThread* mainthread = QCoreApplication::instance()->thread();
    //breakpoint here to check thisthread and mainthread
//    thread->start();
}

Worker* worker = new Worker(mythingy);
QThread* thread = new QThread();
worker->moveToThread(thread);
thread->start();
//wrong: directly invoking doWork in mainthread    
worker->doWork();
//correct: through signal-slot mechanics
connect(this, SIGNAL(startWork()), worker, SLOT(doWork()));