Qt：信號插槽不工作

Question

我正在嘗試在主gui和另一個移動到另一個線程的對象之間實現Signal和Slot系統......以下是類設計的樣子......遺憾的是無法實現它...

MainWindow.h

signals:
    void StopDisplayWidget();
    void StartDisplayWidget();
    void signalFromGUI();

private slots:
    void on_pushButton_start_display_clicked();

    void on_pushButton_stop_display_clicked();

    void on_pushButton_check_clicked();

private:
    Ui::MainWindow *ui;
    displaythread *threadforDisplay;
    display *displayWidget;
    QThread *WorkerDisplay;

MainWindow.cpp

{
    threadforDisplay = new displaythread;
    threadforDisplay->setptr2display(displayWidget);

    WorkerDisplay = new QThread;
    QObject::connect(WorkerDisplay,SIGNAL(started()),threadforDisplay,SLOT(Process()));

    QObject::connect(this,SIGNAL(StartDisplayWidget()),threadforDisplay,SLOT(StartDisplay()));
    QObject::connect(this,SIGNAL(StopDisplayWidget()),threadforDisplay,SLOT(StopDisplay()));
    QObject::connect(this,SIGNAL(signalFromGUI()),threadforDisplay,SLOT(Check()));

    threadforDisplay->moveToThread(WorkerDisplay);
}

void MainWindow::on_pushButton_start_display_clicked()
{
    if(!threadforDisplay->IsDisplayActive())
        emit this->StartDisplayWidget();

    if(!WorkerDisplay->isRunning())
        WorkerDisplay->start();
}

void MainWindow::on_pushButton_stop_display_clicked()
{
    if(threadforDisplay->IsDisplayActive())
    {
        emit this->StopDisplayWidget();
    }
}

void MainWindow::on_pushButton_check_clicked()
{
    std::cout<<"CHECKING SIGNAL SLOT"<<std::endl;
    emit this->signalFromGUI();
}

threadforDisplay是一個指向displaythread類的指針

displaythread.h

#include <QObject>
#include <QWaitCondition>
#include <QMutex>
#include "display.h"

class displaythread : public QObject
{
    Q_OBJECT
public:
    explicit displaythread(QObject *parent = 0);
    bool IsDisplayActive() const;
    void setptr2display(display *);

signals:

public slots:
    void Process();
    void StartDisplay();
    void StopDisplay();
    void Check();


private:
    void SleepThread();

    volatile bool stopped,running;
    QMutex mutex;
    QWaitCondition waitcondition;
    display *displayinGUI;

displaythread.cpp

void displaythread::setptr2display(display *ptr)
{
    displayinGUI = ptr;
}

void displaythread::Process()
{
    std::cout<<"RECEIVED START PROCESS SIGNAL"<<std::endl;
    running = true;
    while(true)
    {
        if(!stopped)
        {
            displayinGUI->update();
            this->SleepThread();
        }
    }

}

void displaythread::SleepThread()
{
    mutex.lock();
    waitcondition.wait(&mutex,20);
    mutex.unlock();
}

void displaythread::StartDisplay()
{
    std::cout<<"RECEIVED START SIGNAL"<<std::endl;
    stopped = false;
    running = true;
}

void displaythread::StopDisplay()
{
    std::cout<<"RECEIVED STOP SIGNAL"<<std::endl;
    stopped = true;
    running = false;
}

bool displaythread::IsDisplayActive() const
{
    return running;
}

void displaythread::Check()
{
    std::cout<<"SIGNAL FROM GUI RECEIVED"<<std::endl;
}

display.h

class display : public QWidget
{
    Q_OBJECT
public:
    explicit display(QWidget *parent = 0);
    ~display();

signals:

public slots:

private:
    void paintEvent(QPaintEvent *);

    IplImage *image_opencvBGR,*image_opencvRGB;
    QImage image;
    CvCapture *webcam;

display.cpp

display::display(QWidget *parent) :
    QWidget(parent)
{
    image_opencvRGB = cvCreateImage(cvSize(640,480),8,3);
    webcam = cvCaptureFromCAM(-1);
}

display::~display()
{
    cvReleaseCapture(&webcam);
}

void display::paintEvent(QPaintEvent *)
{
    //std::cout<<"IN PAINT LOOP"<<std::endl;
    image_opencvBGR = cvQueryFrame(webcam);

    cvCvtColor(image_opencvBGR,image_opencvRGB,CV_BGR2RGB);
    image = QImage((const unsigned char*)image_opencvRGB->imageData,image_opencvRGB->width,image_opencvRGB->height,QImage::Format_RGB888);
    QRectF target(0.0,0.0,image.width(),image.height());
    QRectF source(0.0,0.0,image.width(),image.height());
    QPainter painter(this);
    painter.drawImage(target,image,source);
}

輸出：

收到的啟動過程信號

但是，除了Process槽之外沒有其他插槽工作時，從主gui發出信號，即MainWindow ..它是由於movetoThread命令嗎？ 唐諾，我錯了..

Answer 1

答案很簡單：Qwidgets不在主線程之外工作。 因此，您無法使用displaythread執行GUI代碼。

此外，你的while循環可能會導致問題（我知道變量是易變的，但我沒有時間正確分析它是否正確）

有關更多信息，請參閱文檔 。

ps：看來你的事情太過分了。 重做整個設計。 GUI操作在主線程中。 僅使用線程進行計算。 如果線程和對其變量的訪問之間的通信僅使用信號和插槽，則不需要鎖定機制。