当前位置：首页 > news >正文

Qt线程等待条件QWaitCondition

news 2025/7/19 4:32:00

Qt 线程等待条件

概念

Qt提供了QWaitCondition类实现“等待条件”式的线程控制方法，它让线程阻塞在等待条件的地方，直到条件满足后才继续执行下去。也就是说，QWaitCondition可以使一个线程在满足一定条件时通知其他多个线程，使它们及时作出响应。
QWaitCondition类成员函数

函数名称	函数描述
QWaitCondition()	构造并初始化对象
wai()	解锁互斥量，并阻塞等待唤醒条件
wakeAll()	唤醒所有处于等待状态的线程，线程唤醒的顺序不确定，由操作系统的调度策略决定
wakeOne()	唤醒一个处于等待状态的线程，唤醒哪个线程不确定，由操作系统的调度策略决定
notify_all()	相当于wakeAll().此函数兼容STL
notify_one()	相当于wakeOne().此函数兼容STL

程序示例

读取线程启动进入等待唤醒状态，当写入数据线程写入数据完成后唤醒所有读取线程，读取线程再继续执行；

// 公共数据和锁&等待唤醒对象
class TestData
{
public:
    static int sm_nSharedNumber;
    static QReadWriteLock sm_ReadWriteLock;
    static QWaitCondition sm_WaitCondition;
};

int TestData::sm_nSharedNumber = 10;
QReadWriteLock TestData::sm_ReadWriteLock;
QWaitCondition TestData::sm_WaitCondition;

// 写入数据线程
class WorkThread2 : public QThread
{
    Q_OBJECT
public:
    explicit WorkThread2(QObject *parent = nullptr);
    ~WorkThread2() = default;

protected:
    void run() override;
};

WorkThread2::WorkThread2(QObject *parent) : QThread(parent)
{

}

void WorkThread2::run()
{
    TestData::sm_ReadWriteLock.lockForWrite();
    TestData::sm_nSharedNumber += 5;
    TestData::sm_nSharedNumber *= 10;

    qDebug() << QString::fromLocal8Bit("write1 ----- 线程2 ID:") << QThread::currentThreadId() << "Result = " << TestData::sm_nSharedNumber;
    qDebug() << QString::fromLocal8Bit("write2 ----- 线程2 ID:") << QThread::currentThreadId() << "Result = " << TestData::sm_nSharedNumber;
    qDebug() << QString::fromLocal8Bit("write3 ----- 线程2 ID:") << QThread::currentThreadId() << "Result = " << TestData::sm_nSharedNumber;

    TestData::sm_WaitCondition.wakeAll();
    TestData::sm_ReadWriteLock.unlock();
}

// 读取数据线程
class WorkThread1 : public QThread
{
    Q_OBJECT
public:
    explicit WorkThread1(QObject *parent = nullptr);
    ~WorkThread1() = default;

protected:
    void run() override;

};

WorkThread1::WorkThread1(QObject *parent) : QThread(parent)
{

}

void WorkThread1::run()
{
    TestData::sm_ReadWriteLock.lockForRead();

    // 先解锁 QReadWriteLock ，其他线程可以使用 QReadWriteLock
    TestData::sm_WaitCondition.wait(&TestData::sm_ReadWriteLock);

    qDebug() << QString::fromLocal8Bit("read1 ----- 线程1 ID:") << QThread::currentThreadId() << "Result = " << TestData::sm_nSharedNumber;
    msleep(10);
    qDebug() << QString::fromLocal8Bit("read2 ----- 线程1 ID:") << QThread::currentThreadId() << "Result = " << TestData::sm_nSharedNumber;
    msleep(20);
    qDebug() << QString::fromLocal8Bit("read3 ----- 线程1 ID:") << QThread::currentThreadId() << "Result = " << TestData::sm_nSharedNumber;

    TestData::sm_ReadWriteLock.unlock();
}

// 测试函数
void Test()
{
    unique_ptr<WorkThread1> upThread11 = std::make_unique<WorkThread1>();
    unique_ptr<WorkThread1> upThread12 = std::make_unique<WorkThread1>();
    unique_ptr<WorkThread1> upThread13 = std::make_unique<WorkThread1>();

    unique_ptr<WorkThread2> upThread2 = std::make_unique<WorkThread2>();

	// 先启动读取函数，让函数处在等待阻塞状态
    upThread11->start();
    upThread12->start();
    upThread13->start();

    QThread::msleep(10);

    upThread2->start();

    upThread11->wait();
    upThread12->wait();
    upThread13->wait();
    upThread2->wait();

    qDebug() << "Over!";
}