C ++ Qt GUI更新

Question

我是Qt的新手，所以我被GUI更新卡住了。 我有2個類：主線程中的ControlWidget和單獨線程中的CameraController 。

int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    CameraController *cameraController = new CameraController;;
    ControlWidget *main_window = new ControlWidget;
    Thread getImageThread; 
    cameraController->moveToThread(&getImageThread);
    getImageThread.start();
    QTimer get_images_timer;
    QObject::connect(&get_images_timer, SIGNAL(timeout()), cameraController, SLOT(onTimerOut()), Qt::QueuedConnection);
    QObject::connect(cameraController, SIGNAL(sendLabel(QImage)), main_window, SLOT(getImage(QImage)), Qt::QueuedConnection);
    QObject::connect(&get_images_timer, SIGNAL(timeout()), main_window, SLOT(update()), Qt::QueuedConnection);
    get_images_timer.start(2000);
    app.exec();
    return 0;
}

因此，我想每2秒從攝像機線程獲取圖像並將其發送到主線程（這確實發生了，所以我在main_window對象上有了QImage ）。 然后，我想將此QImage放入cam1和cam2 QLabel 。 我被困在這里：

首先：當我使用setPixmap()方法時， QLabel.width()和QLabel.height()是不同的，然后image.width() image.height()和image.height()或pixmap.width()和pixmap.height() 。

第二：我無法可視化QLabel 。 如果我執行此操作- this->ImageLayout->addWidget(cam1)什么都沒有發生。 this->update也無濟於事。

我需要額外的GUI更新工作人員嗎？ 我究竟做錯了什么？

源代碼以獲取更多信息：

CameraController.h

class CameraController : public QObject
{
    Q_OBJECT 
private: 
    CoreApi::InstanceHandle g_hApi;
    CoreApi::DeviceCollectionHandle hDeviceCollection;
    CoreApi::DeviceHandle hDevice;
    CoreApi::CameraPortHandle first_cam;
    Common::FrameHandle frame;
    QPixmap pixmap;
    QImage image;
public: 
    CameraController();
    ~CameraController();
    QLabel outLabel;
public slots:
    void onTimerOut();
signals:
    QImage sendLabel(QImage image);
};

CameraController.cpp

CameraController::CameraController()
{
    try
    {
        this->g_hApi = CoreApi::Instance::initialize();
        this->hDeviceCollection = this->g_hApi->deviceCollection();
        this->hDevice = hDeviceCollection->device(0);
        this->first_cam = hDevice->cameraPort(0);
        first_cam->autoConfigure();
        first_cam->liveStart();
    }
    catch (GeneralException& e)
    {
    std::cout << e.what() << std::endl;
    }
}

CameraController::~CameraController()
{
}

void CameraController::onTimerOut()
{
    if (this->first_cam->liveFrameReady())
    {
        this->frame = first_cam->liveFrame();
        this->image =  QImage((uchar*)this->frame->buffer()->data(), this->frame->dataType()->width(), this->frame->dataType()->height(), QImage::Format::Format_RGB888);
        this->image = this->image.scaled(QSize(this->image.width()/10, this->image.height()/10));
        std::cout << "width = "<<this->image.width() << "height = " << this->image.height() << std::endl;
        emit sendLabel(this->image.copy());
    }
}

ControlWidget.h

class ControlWidget :public QDialog
{
    Q_OBJECT
private:
    QGLCanvas *osCanvas;
    QGridLayout *mainLayout;
    QGridLayout *buttonLayout;
    QVBoxLayout *imageLayout, *settingsLayout;
    QHBoxLayout *controlLayout;
    QListWidget *cameraListWidget, *devicesListWidget;
    QLabel *cameraListLabel, *devicesListLabel, *cameraSettingsLabel, *fpsLabel, *shutterLabel;
    QHBoxLayout *fpsLayout, *shutterLayout;
    QLineEdit *fpsEdit, *shutterEdit;
    QPushButton *saveButton, *saveSettingButton, *applySettingsButton, *chooseFolderButton;
    QTimer* m_timer;
public:
    ControlWidget(QWidget *parent = 0);
    ~ControlWidget();
    QLabel *cam1, *cam2;
    QImage *camera_1, *camera_2;
    void createWidgets();
public slots:
    void getImage(QImage new_frame);
    void displayImages();
signals: 
    void images_loaded();
private slots:
    void onTimeout()
    {
        qDebug() << "Worker::onTimeout get called from controlWidget timer and  ?: " << QThread::currentThreadId();
    };
};

ControlWidget.cpp

ControlWidget::ControlWidget(QWidget *parent)
{
    this->createWidgets();
    this->m_timer = new QTimer;
    connect(this->m_timer, SIGNAL(timeout()),this, SLOT(update()));
    m_timer->start(1000);
}

ControlWidget::~ControlWidget()
{
    delete this->mainLayout;
}


void ControlWidget::createWidgets() 
{
    this->imageLayout = new QVBoxLayout;
    this->cam1 = new QLabel;
    this->cam2 = new QLabel;
    this->imageLayout->addWidget(cam1);
    this->imageLayout->addWidget(cam2);
    this->setLayout(this->imageLayout);
    this->show();
}

void ControlWidget::displayImages()
{
    QLabel tmp_label ;

    std::cout << "********************************************************************************" << std::endl;
    std::cout <<"  camera height  = " <<this->camera_1->height() << "   camera width = " << this->camera_1->width() << std::endl;
    std::cout << "********************************************************************************" << std::endl;
    QPixmap tmp_pixmap = QPixmap::fromImage(this->camera_1->copy());
    std::cout << "PIXMAP WIDTH = " << tmp_pixmap.width() << "Pixmap Height = " << tmp_pixmap.height() <<std::endl;
    std::cout << "LABELWIDTH = "<< tmp_label.width() << "LabelHeight =  "<< tmp_label.height() << std::endl;
    tmp_label.setGeometry(200, 200, tmp_pixmap.width(), tmp_pixmap.height());
    tmp_label.show();
    this->cam1 = &tmp_label;
    this->cam2 = &tmp_label;
    std::cout << "CAM1 Width = " <<this->cam1->width() << std::endl;
    this->imageLayout->addWidget(this->cam1);
    this->imageLayout->addWidget(this->cam2);
}



void ControlWidget::getImage(QImage img)
{
    std::cout << "********************************************************************************" << std::endl;
    std::cout << "  img height  = " << img.height() << "   img width = " << img.width() << std::endl;
    std::cout << "********************************************************************************" << std::endl;
    this->camera_1 = &QImage(img);
    this->camera_2 = &QImage(img);
    this->displayImages();
}

Answer 1

好的，所以這里有一些設計問題：

1. tmp_label在堆棧上創建，並且無論如何都會在displayImages方法的末尾銷毀

2. 每次收到新的相機框架時，您都嘗試使用this->imageLayout->addWidget(this->cam1);將QLabels添加回您的UI this->imageLayout->addWidget(this->cam1); 。 而是在構造窗口小部件時添加一次，然后僅使用cam1->setPixmap(...) 。

3. 也許我錯過了，但是我看不到您在QLabel中設置圖像的位置。 這通常是通過QLabel::setPixmap

接着：

• 當像您一樣依賴標准小部件時，不需要調用update() ，QLabel在設置其像素圖時會自動更新
• 您實際上不需要在C ++中使用this->
• 我不知道您的Thread類下有什么內容，但是當使用QThreads時，您不需要為連接傳遞Qt::QueuedConnection參數，這是自動完成的
• 要排除與如何實例化UI或使用布局有關的問題，請首先嘗試使用基於Qt Designer .ui的靜態界面
• 實際上，您可以使用QPixmap::save("image.jpg")或QImage::save("image.jpg")輕松測試所讀取的QPixmap和QImage的有效性。

Answer 2

除了@basslo注釋之外，請勿執行此操作- this->cam1 = &tmp_label; 。 當tmp_label被銷毀（它是一個局部變量）時，它也將從其所屬的布局中刪除，因此它永遠不會被實際顯示。

使用this->cam1->setPixmap(...)代替分配新圖像，並定義大小策略，以從構造擴展到擴展（ 此答案提供了有關它的更多信息）。