QT通过C++线程池运行Lambda自定义函数流程详解

#ifndef THREAD_POOL_H
#define THREAD_POOL_H
#include <vector>
#include <queue>
#include <memory>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <future>
#include <functional>
#include <stdexcept>
class ThreadPool {
public:
    ThreadPool(size_t);
    template<class F, class... Args>
    auto enqueue(F&& f, Args&&... args)
        -> std::future<typename std::result_of<F(Args...)>::type>;
    ~ThreadPool();
private:
    // need to keep track of threads so we can join them
    std::vector< std::thread > workers;
    // the task queue
    std::queue< std::function<void()> > tasks;
    // synchronization
    std::mutex queue_mutex;
    std::condition_variable condition;
    bool stop;
};
// the constructor just launches some amount of workers
inline ThreadPool::ThreadPool(size_t threads)
    :   stop(false)
{
    for(size_t i = 0;i<threads;++i)
        workers.emplace_back(
            [this]
            {
                for(;;)
                {
                    std::function<void()> task;
                    {
                        std::unique_lock<std::mutex> lock(this->queue_mutex);
                        this->condition.wait(lock,
                            [this]{ return this->stop || !this->tasks.empty(); });
                        if(this->stop && this->tasks.empty())
                            return;
                        task = std::move(this->tasks.front());
                        this->tasks.pop();
                    }

                    task();
                }
            }
        );
}
// add new work item to the pool
template<class F, class... Args>
auto ThreadPool::enqueue(F&& f, Args&&... args)
    -> std::future<typename std::result_of<F(Args...)>::type>
{
    using return_type = typename std::result_of<F(Args...)>::type;
    auto task = std::make_shared< std::packaged_task<return_type()> >(
            std::bind(std::forward<F>(f), std::forward<Args>(args)...)
        );
    std::future<return_type> res = task->get_future();
    {
        std::unique_lock<std::mutex> lock(queue_mutex);
        // don't allow enqueueing after stopping the pool
        if(stop)
            throw std::runtime_error("enqueue on stopped ThreadPool");
        tasks.emplace([task](){ (*task)(); });
    }
    condition.notify_one();
    return res;
}
// the destructor joins all threads
inline ThreadPool::~ThreadPool()
{
    {
        std::unique_lock<std::mutex> lock(queue_mutex);
        stop = true;
    }
    condition.notify_all();
    for(std::thread &worker: workers)
        worker.join();
}
#endif  // THREAD_POOL_H

#ifndef LOADFUNCOPERATE_H
#define LOADFUNCOPERATE_H
#include <QDialog>
#include <unistd.h>
#include "threadpool.h"
namespace Ui {
class LoadFuncOperate;
}
class LoadFuncOperate : public QDialog
{
    Q_OBJECT
public:
    explicit LoadFuncOperate(QDialog *parent = nullptr);
    ~LoadFuncOperate();
    // 设置需要运行的函数
    void setOperateFunc(std::function<void()> userThreadOperateFunc);
    // 设置显示标题
    void setTitleHint(const std::string str);
private:
    Ui::LoadFuncOperate *ui;
    std::function<void()> m_pThreadFunction;        // 存储用户设置的函数
    std::shared_ptr<ThreadPool> m_pThreadPools;     // 智能指针定义线程池
};
#endif // LOADFUNCOPERATE_H

#include "LoadFuncOperate.h"
#include "ui_LoadFuncOperate.h"
#include <QMovie>
LoadFuncOperate::LoadFuncOperate(QDialog *parent) :
    QDialog(parent),
    ui(new Ui::LoadFuncOperate)
{
    ui->setupUi(this);
    setWindowFlags(Qt::Tool | Qt::FramelessWindowHint | Qt::WindowStaysOnTopHint);
    // 设置窗体关闭时自动释放内存
    this->setAttribute(Qt::WA_DeleteOnClose);
    // 初始化智能指针线程池
    m_pThreadPools = std::make_shared<ThreadPool>(2);
    // 设置动图
    QMovie *movie = new QMovie(this);
    movie->setFileName(":/msgbox/pro.gif");     // 设置显示的gif图(先将gif添加到资源文件)
    QSize pSize(301, 20);           // Label大小
    ui->label_2->setMovie(movie);   // Label设置动图
    movie->setScaledSize(pSize);    // QMovie设在大小与Label一致
    movie->start();                 // 启动
}
LoadFuncOperate::~LoadFuncOperate()
{
    delete ui;
}
void LoadFuncOperate::setOperateFunc(std::function<void ()> userThreadOperateFunc)
{
    m_pThreadFunction = userThreadOperateFunc;
    auto Fun = [=]()
    {
        if (m_pThreadFunction)
        {
            sleep(1);
            m_pThreadFunction();    // 执行函数
            done(1);                // exec()运行窗体后返回1
            this->close();
        }
    };
    // 运行调用
    m_pThreadPools->enqueue(Fun);
}
void LoadFuncOperate::setTitleHint(const std::string str)
{
    ui->label->setText(QString::fromStdString(str));
}

public:
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
	// 封装
    int ShowLoadingDlg(std::function<void ()> pUserThreadFunction, const std::string &strTips);
    // 测试
    void testLoadFuncOperate();

void MainWindow::testLoadFuncOperate()
{
    int a = 1;
    int b = 2;
    int c;
    auto userThreadFunction = [&]()
    {
        printf("在线程中执行函数...\n");
        for (int i = 0; i < 5; i++) {
            a+=2;
            b--;
            printf("在线程中执行函数...  %d\n", i);
        }
        c = a + b;
        // 此处省略一万行代码
        sleep(3);
        /* 这里可以有一个判断，如果某个条件变量被修改了，就return退出 */
        /*
			if (true == this->indexFlag) {
				return;
			}
		*/
		// 此处还省略一万行代码，此时如果上面退出了，这一万行代码就没法执行了
		// 正常使用法，应该是auto userThreadFunction 一进来就应该是一个for循环在不断运行，当遇到true == this->indexFlag，
		// 就break掉，也就不会再继续for循环了！

        printf("线程中执行函数结束\n");
    };
    ShowLoadingDlg(userThreadFunction, "使用线程池执行函数中...");
    printf("c = %d\n", c);
}
int MainWindow::ShowLoadingDlg(std::function<void ()> pUserThreadFunction, const std::string &strTips)
{
    LoadFuncOperate *operateFunc = new LoadFuncOperate;
    operateFunc->setOperateFunc(pUserThreadFunction);
    operateFunc->setTitleHint(strTips);
    operateFunc->setModal(true);
    int nRes = operateFunc->exec();
    return nRes;
}

protected:
    void mouseMoveEvent(QMouseEvent *event) override;
    void mousePressEvent(QMouseEvent *event) override;
    void mouseReleaseEvent(QMouseEvent *event) override;
private:
	bool m_mousePress;      /* 鼠标按下 */
	QPoint m_widgetPos;
/* 方法实现 */
void LoadFuncOperate::mouseMoveEvent(QMouseEvent* event)
{
    if (m_mousePress) {
        move(event->pos() - m_widgetPos + this->pos());
    }
}
void LoadFuncOperate::mousePressEvent(QMouseEvent* event)
{
    if (event->button() == Qt::MouseButton::LeftButton) {
        m_widgetPos = event->pos();
        m_mousePress = true;
    }
}
void LoadFuncOperate::mouseReleaseEvent(QMouseEvent* event)
{
    m_mousePress = false;
}