Qt中多线程QThread、QThreadPool、QConCurrent三种方式对比分析

#include <QCoreApplication>
#include <QThread>
#include <QObject>
#include <QDebug>
// 1. 定义工作类（千万不要继承QThread）
class Worker : public QObject {
    Q_OBJECT
public:
    explicit Worker(int id) : m_id(id) {}
public slots:
    // 槽函数：执行耗时任务
    void doWork() {
        qDebug() << "Worker" << m_id << "running in thread:" << QThread::currentThreadId();
        QThread::msleep(1000); // 模拟耗时操作
        int result = m_id * 100; // 模拟计算结果
        emit resultReady(m_id, result); // 发送结果信号
    }
signals:
    void resultReady(int id, int result);
private:
    int m_id;
};
int main(int argc, char *argv[]) {
    QCoreApplication a(argc, argv);
    qDebug() << "Main thread:" << QThread::currentThreadId();
    QList<QThread*> threads;
    QList<Worker*> workers;
    // 创建 5 个工作对象和 5 个线程
    for (int i = 0; i < 5; ++i) {
        Worker *worker = new Worker(i);
        QThread *thread = new QThread();
        worker->moveToThread(thread); // 将工作对象移入新线程
        // 连接启动信号：线程启动后，调用 worker 的 doWork
        QObject::connect(thread, &QThread::started, worker, &Worker::doWork);
        // 连接结果信号：将结果打印到主线程
        QObject::connect(worker, &Worker::resultReady, [](int id, int result){
            qDebug() << "  -> Got result from Worker" << id << ":" << result;
        });
        // 连接清理信号：任务完成后，安全退出线程并清理内存
        QObject::connect(worker, &Worker::resultReady, thread, &QThread::quit);
        QObject::connect(thread, &QThread::finished, worker, &QObject::deleteLater);
        QObject::connect(thread, &QThread::finished, thread, &QObject::deleteLater);
        threads.append(thread);
        workers.append(worker);
    }
    // 启动所有线程
    for (QThread *t : threads) {
        t->start();
    }
    return a.exec();
}

#include <QCoreApplication>
#include <QThreadPool>
#include <QRunnable>
#include <QDebug>
// 1. 定义任务类
class ComputeTask : public QRunnable {
public:
    ComputeTask(int id, std::function<void(int, int)> callback) 
        : m_id(id), m_callback(callback) 
    {
        // 设置任务执行完后自动销毁，防止内存泄漏
        setAutoDelete(true); 
    }
    // 重写 run 函数
    void run() override {
        qDebug() << "Task" << m_id << "running in thread:" << QThread::currentThreadId();
        QThread::msleep(1000); // 模拟耗时操作
        int result = m_id * 100;
        // QRunnable 没有信号槽，使用回调函数将结果传回
        if (m_callback) {
            m_callback(m_id, result);
        }
    }
private:
    int m_id;
    std::function<void(int, int)> m_callback;
};
int main(int argc, char *argv[]) {
    QCoreApplication a(argc, argv);
    qDebug() << "Main thread:" << QThread::currentThreadId();
    // 设置全局线程池最大线程数为 2（为了演示线程复用）
    QThreadPool::globalInstance()->setMaxThreadCount(2);
    for (int i = 0; i < 5; ++i) {
        // 定义回调函数接收结果
        auto callback = [](int id, int result) {
            qDebug() << "  -> Got result from Task" << id << ":" << result;
        };
        ComputeTask *task = new ComputeTask(i, callback);
        // 丢给线程池执行
        QThreadPool::globalInstance()->start(task);
    }
    // 等待所有任务完成再退出（仅为了演示，实际GUI程序不推荐主线程wait）
    QThreadPool::globalInstance()->waitForDone();
    qDebug() << "All tasks finished.";
    return 0; // 不需要 a.exec()，因为没有事件循环
}

#include <QCoreApplication>
#include <QtConcurrent>
#include <QFutureWatcher>
#include <QDebug>
int main(int argc, char *argv[]) {
    QCoreApplication a(argc, argv);
    qDebug() << "Main thread:" << QThread::currentThreadId();
    // 同样限制全局线程池大小以便观察
    QThreadPool::globalInstance()->setMaxThreadCount(2);
    // 使用 QFutureWatcher 监听异步结果（因为 QtConcurrent 本身是非阻塞的）
    QFutureWatcher<int> *watcher = new QFutureWatcher<int>();
    // 当单个结果就绪时触发
    QObject::connect(watcher, &QFutureWatcher<int>::resultReadyAt, [](int index) {
        qDebug() << "  -> Result at index" << index << "is ready.";
    });
    // 当所有任务完成时触发
    QObject::connect(watcher, &QFutureWatcher<int>::finished, [watcher]() {
        qDebug() << "All concurrent tasks finished.";
        // 获取所有结果
        QFuture<int> future = watcher->future();
        for (int i = 0; i < future.resultCount(); ++i) {
            qDebug() << "    Final Result[" << i << "] =" << future.resultAt(i);
        }
        watcher->deleteLater();
        QCoreApplication::quit(); // 退出程序
    });
    // 使用 QtConcurrent::run 启动并发任务
    // 返回 QFuture 对象用于跟踪状态
    QFuture<int> future = QtConcurrent::mapped(QList<int>() << 0 << 1 << 2 << 3 << 4, [](int id) -> int {
        qDebug() << "Concurrent task" << id << "running in thread:" << QThread::currentThreadId();
        QThread::msleep(1000); // 模拟耗时
        return id * 100;       // 直接返回结果
    });
    // 将 future 交给 watcher 监控
    watcher->setFuture(future);
    return a.exec();
}