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Qt6多线程问题

qt6 qthread qt multithreading

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Mark · 技术社区 · 3 年前

我在看书 this this 博士。

基本上我有这个功能:

bool Flow::checkNfc()
{
    QByteArray id;
    QByteArray data;

    bool ret = _nfc.read(&id, &data, 8);
    if (ret)
    {
        // do something
    }

    return ret;
}

bool ret = _nfc.read(&id, &data, 8);

轮流打电话 libnfc 阻止当前线程的函数。

因为两者 checkNfc 和 _nfc.read 函数需要与主线程交换数据,我不确定是否可以使用 QFutureWatcher 方法我试过这样的方法:

QFutureWatcher<bool> watcher;
QFuture<bool> future = QtConcurrent::run(&MyProject::checkNfc);
watcher.setFuture(bool);

所以我想试试这个 QThread 解决方案问题在于,对于真实案例场景来说,示例过于简单:

class Worker : public QObject
{
    Q_OBJECT

public slots:
    void doWork(const QString &parameter) {
        QString result;
        /* ... here is the expensive or blocking operation ... */
        emit resultReady(result);
    }

signals:
    void resultReady(const QString &result);
};

不管怎样,我试过了,在我的主要课堂上,我写道:

private:
    QThread _nfcThread;
    MyNfc _nfc;

private slots:
    void nfc_readResult(bool success, QByteArray id, QByteArray data);

_nfc.moveToThread(&_nfcThread);
connect(&_nfcThread, &QThread::finished, &_nfc, &QObject::deleteLater);
connect(&_nfc, &MyNfc::resultRead, this, &MyProject::nfc_readResult);
_nfcThread.start();

并从计时器插槽:

_nfc.doWork();

在MyNfc中:

signals:
    void resultRead(bool result, QByteArray id, QByteArray data);

public slots:
    void doWork();

void MyNfc::doWork()
{
    QByteArray id;
    QByteArray data;

    bool ret = read(&id, &data, 8);
    emit resultRead(ret, id, data);
}

一切都还在继续。。。但我的主应用程序仍然会在每次调用时阻塞 doWork() .

我错过了什么?

1 回复 | 直到 3 年前

1

HiFile.app - best file manager 3 年前

你不能打电话 doWork()

因此,触发辅助线程执行工作的正确方法是以下连接:

connect(&_nfcThread, &QThread::started, &_nfc, &MyNfc::doWork);

嫁妆 .

deleteLater() deleteLater()

_nfc.moveToThread(&_nfcThread);
connect(&_nfcThread, &QThread::started, &_nfc, &MyNfc::doWork); // this starts the worker
connect(&_nfc, &MyNfc::resultRead, this, &MyProject::nfc_readResult); // this passes the result
connect(&_nfc, &MyNfc::resultRead, &_nfcThread, &QThread::quit); // this will quit the event loop in the thread
_nfcThread.start();

更新:如果要定期调用插槽,请连接计时器。当工作完成时,不要退出线程。最简单的情况是:

_nfc.moveToThread(&_nfcThread);
connect(&_nfcThread, &QThread::started, &_timer, &QTimer::start); // this starts the timer after the thread is ready
connect(&_timer, &QTimer::timeout, &_nfc, &MyNfc::doWork); // start work at timer ticks
connect(&_nfc, &MyNfc::resultRead, this, &MyProject::nfc_readResult); // this passes the result
_nfcThread.start();

但是,由于没有退出事件循环,因此需要在删除线程之前手动退出它。最好的位置是在主类的析构函数中。

MainClass::~MainClass()
{
  _nfcThread.quit(); // this schedules quitting of the event loop when the thread gets its current work done
  _nfcThread.wait(); // this waits for it, this is important! you cannot delete a thread while it is working on something.
  // ... because the thread (and the worker too) will get deleted immediately once this destructor body finishes, which is... right now!
}