c++ - 如何从另一个线程中引发的 Boost 信号更新 Qt GUI？

Question

acquisitionStageChangedEvent我有一个普通的 C++ 对象，它在单独的线程中运行数据采集例程，并使用带有以下签名的 Boost 信号通知进程： boost::signal2::signal<void(const std::string &)>. 如何在新线程中开始采集并使用此信息更新 UI 而不会出现跨线程异常？

Answer 1

在信号处理程序中将an 设置std::atomic<bool>为 true 并从QTimer.

Answer 2

这是一个关于如何在进度更新期间和任务结束时启动后台线程和更新 UI 的工作示例：

namespace Ui
{
    class DtacqAcquisitionWidget;
}

class DtacqAcquisitionWidget : public QWidget
{
    Q_OBJECT

public:
    explicit AcquisitionWidget(QWidget *parent = 0);

   ~DtacqAcquisitionWidget();

private slots:

    void on_pushButtonStart_clicked();

    void onDtacqChangeState(const QString &stage);

    /*... Other slots here */
private:
    Ui::AcquisitionWidget *ui;

    QFutureWatcher<void>  *m_future_watcher; // This is to be able to run UI code at the end of the background thread

    anlytcs::Dt100Acq m_dtacq; // The plain C++ object that raises the boost signal 'acquisitionStageChangedEvent'
};

在 .cpp 文件中：

DtacqAcquisitionWidget::DtacqAcquisitionWidget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::DtacqAcquisitionWidget)
{
    ui->setupUi(this);

    // Run the 'onAcquisitionFinished' slot at the end of the thread
    m_future_watcher = new QFutureWatcher<void>(this);
    connect(m_future_watcher, SIGNAL(finished()), this, SLOT(onAcquisitionFinished()));

    // Acquisition stages update
    m_dtacq.acquisitionStageChangedEvent.connect([this](const std::string &stage)
    {
        this->onDtacqChangeState(QString::fromStdString(stage));
    });
}

void DtacqAcquisitionWidget::on_pushButtonStart_clicked()  // Starting the acquisition
{
    ui->pushButtonStop->setEnabled(true);
    ui->pushButtonStart->setEnabled(false);
    ui->progressBar->setValue(0);

    // Start the acquisition in a new thread
    QFuture<void> f = QtConcurrent::run(this, &DtacqAcquisitionWidget::acquireChannelData);    
    m_future_watcher->setFuture(f);
}

void DtacqAcquisitionWidget::onDtacqChangeState(const QString &stage)
{
    if (thread() != QThread::currentThread())
    {      
        QMetaObject::invokeMethod(this, "onDtacqChangeState", 
            Qt::BlockingQueuedConnection, Q_ARG(QString, stage));
    }
    else
    {
        ui->labelDtacqState->setText(stage);
        ui->progressBar->setValue(ui->progressBar->value() + 40);
    }    
}

void DtacqAcquisitionWidget::onAcquisitionFinished()
{
    // Set what to update here in the GUI here when the acquisition thread finishes     
    ui->labelDtacqState->setText("DONE!");
}

void DtacqAcquisitionWidget::acquireChannelData()
{
    // This is running on a background thread (Non UI thread)
    double time_sec = ui->spinBoxAcqTimeSec->value();
    uint32_t channel_mask = getChannelMask();

    std::string data_path = "C:/Users/pardinad/Desktop/DtacqData/";
    m_dtacq.startAcquisition(time_sec, channel_mask, 250);
    ui->labelDtacqState->setText("Acquisition Started!");

    if(m_dtacq.completeAcquisition())   
    {
        for (auto & dch : m_dtacq.dataChannels())
        {
            std::stringstream ss;
            ss << data_path << std::setw(2) << std::setfill('0') << dch.channelNumber() << ".DAT";
            std::string ch_file = ss.str();
            dch.saveToFile(ch_file);
        }
    }
}