Question

我有一个普通的C ++对象，它在一个单独的线程中运行一个数据采集例程，并使用一个名为acquisitionStageChangedEvent的Boost信号通知进程，该信号具有以下签名：boost::signal2::signal<void(const std::string &)>。如何在新线程中开始获取并使用此信息更新UI而不会出现跨线程异常？

Answer 1

在信号处理程序中将std::atomic<bool>设置为true，并从QTimer检查该标记。

Answer 2

以下是有关如何在进度更新期间和任务结束时启动后台线程并更新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);
        }
    }
}

如何从另一个线程中引发的Boost信号更新Qt GUI？

2 个答案: