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Error while initializing the Object in Qt

  • Re: Calling an object from another class

    I want an object of qMRMLSliceControllerWidget in qMRMLSliceWidget.

    1. In the header file I declared the object (qMRMLSliceControllerWidget* scw_temp1;) and in the .cxx file I initialized the object
      (scw_temp1 = new qMRMLSliceControllerWidget(q)).
      error: Screenshot (293).png
    2. I even tried creating a static Get() method in qMRMLSliceControllerWidget which return object of this class, even then I am getting errors.
      Screenshot (288).png

  • Lifetime Qt Champion


    Are you sure you are using the right types?
    The first error seems to say cannot make an A into B.
    SlideWidget versus SlideControllerWidget

    But for test :
    if you make a

    in qMRMLSliceWidget.cpp

    void test () {
    qMRMLSliceControllerWidget test;

    will it accept it ?

    Ofc with the right include etc.

    if still no. Then you might have a circular include where
    qMRMLSliceWidget includes qMRMLSliceControllerWidget and reverse.

  • I tried using test() method:
    Screenshot (302).png
    I have a doubt even in test() method we are just declaring the object right, we are not initializing. My doubt is how to initialize the object.
    For accessing the widgets in qMRMLSliceControllerWidget I will have to create its object right? or is there any other method.

  • @Meera-Hadid said in Error while initializing the Object in Qt:

    I tried using test() method

    The error message indicates that, whatever code you have written, you are attempting to access a variable named test when you say you declared a method named test().

  • Screenshot (304).png
    using test object i tried calling the spinBox in qMRMLSliceControllerWidget

    qMRMLSliceControllerWidgetPrivate* qMRMLSliceWidget::test() {
        qMRMLSliceControllerWidgetPrivate* test;
        return test;
    test_obj = qMRMLSliceWidget::test();
      this->ControllerLayout = new QVBoxLayout(q);
      QMargins cmargins = this->ControllerLayout->contentsMargins();

  • Lifetime Qt Champion



    we should not name both object and function test. sorry my bad, too little coffe :)

    I meant

    void test () {
    qMRMLSliceControllerWidget mySC;

    it was just to see if it does know the type without errors.

    Well its just a local variable so it is initialized as such. ( even there is no new )

    It seems it does know the type and does not complain about it ? , correct ?

    So this seems to be fine so you should be able to create
    a qMRMLSliceWidget in qMRMLSliceWidget.

    I think what ever the q is you are giving it
    new qMRMLSliceControllerWidget(q)) <<<< i think its not what it wants

    hence the error in the picture

  • Lifetime Qt Champion

    the code you just posted will crash :)
    Its dangling pointer.

    qMRMLSliceControllerWidgetPrivate* qMRMLSliceWidget::test() {
    qMRMLSliceControllerWidgetPrivate* test; <<<<< dangling pointer !
    return test;

    so that will not work 100%

    it must be
    qMRMLSliceControllerWidgetPrivate* qMRMLSliceWidget::test() {
    qMRMLSliceControllerWidgetPrivate* test = new qMRMLSliceControllerWidgetPrivate( what ever it wants)
    return test;

    ps. why you go from qMRMLSliceControllerWidget to
    qMRMLSliceControllerWidgetPrivate `?
    the private type seems its called that as one should not use it outside class ?

  • Basically the spinBox is defined in qMRMLSliceControllerWidgetPrivate but it is a public variable. For better understanding


    #ifndef __qMRMLSliceControllerWidget_p_h
    #define __qMRMLSliceControllerWidget_p_h
    // CTK includes
    #include <ctkPimpl.h>
    #include <ctkVTKObject.h>
    // qMRML includes
    #include "qMRMLSliceControllerWidget.h"
    #include "qMRMLViewControllerBar_p.h"
    #include "ui_qMRMLSliceControllerWidget.h"
    // MRMLLogic includes
    #include <vtkMRMLSliceLogic.h>
    // VTK includes
    #include <vtkAlgorithmOutput.h>
    #include <vtkCollection.h>
    #include <vtkImageData.h>
    #include <vtkSmartPointer.h>
    #include <vtkWeakPointer.h>
    class ctkSignalMapper;
    class ctkDoubleSpinBox;
    class ctkVTKSliceView;
    class QSpinBox;
    class qMRMLSliderWidget;
    class vtkMRMLSliceNode;
    class vtkObject;
    class vtkMRMLSegmentationDisplayNode;
    struct QMRML_WIDGETS_EXPORT qMRMLOrientation
      QString Prefix;
      QString ToolTip;
    class QMRML_WIDGETS_EXPORT qMRMLSliceControllerWidgetPrivate
      : public qMRMLViewControllerBarPrivate
      , public Ui_qMRMLSliceControllerWidget
      typedef qMRMLSliceControllerWidgetPrivate Self;
      typedef qMRMLViewControllerBarPrivate Superclass;
      qMRMLSliceControllerWidgetPrivate(qMRMLSliceControllerWidget& object);
      ~qMRMLSliceControllerWidgetPrivate() override;
      void init() override;
      void setColor(QColor color) override;
      void setupLinkedOptionsMenu();
      void setupReformatOptionsMenu();
      void setupLightboxMenu();
      void setupCompositingMenu();
      void setupSliceSpacingMenu();
      void setupSliceModelMenu();
      void setupSegmentationMenu();
      void setupLabelMapMenu();
      void setupMoreOptionsMenu();
      void setupOrientationMarkerMenu();
      void setupRulerMenu();
      qMRMLOrientation mrmlOrientation(const QString& name);
      vtkSmartPointer<vtkCollection> saveNodesForUndo(const QString& nodeTypes);
      void enableLayerWidgets();
      vtkMRMLSliceLogic* compositeNodeLogic(vtkMRMLSliceCompositeNode* node);
      vtkMRMLSliceLogic* sliceNodeLogic(vtkMRMLSliceNode* node);
      void setForegroundInterpolation(vtkMRMLSliceLogic* logic, bool interpolate);
      void setBackgroundInterpolation(vtkMRMLSliceLogic* logic, bool interpolate);
      /// Create a list of orientation containing the regular presets and also
      /// the "Reformat" string if sliceToRAS is different one of the preset.
      static void updateSliceOrientationSelector(
          vtkMRMLSliceNode* sliceNode, QComboBox *sliceOrientationSelector);
      //static qMRMLSliceControllerWidgetPrivate* Get();
    public slots:
      /// Update widget state when the scene is modified
      void updateFromMRMLScene();
      /// Update widget state using the associated MRML slice node
      void updateWidgetFromMRMLSliceNode();
      /// Update widget state using the associated MRML slice composite node
      void updateWidgetFromMRMLSliceCompositeNode();
      /// Called after a foreground layer volume node is selected
      /// using the associated qMRMLNodeComboBox
      void onForegroundLayerNodeSelected(vtkMRMLNode* node);
      /// Called after a background layer volume node is selected
      /// using the associated qMRMLNodeComboBox
      void onBackgroundLayerNodeSelected(vtkMRMLNode* node);
      /// Called after a label layer volume node is selected
      /// using the associated qMRMLNodeComboBox
      void onLabelMapNodeSelected(vtkMRMLNode* node);
      /// Called after a segmentation node is selected in the combobox
      void onSegmentationNodeSelected(vtkMRMLNode* node);
      /// Called after the currently selected segmentation node's display
      /// option is modified
      void onSegmentationNodeDisplayModifiedEvent(vtkObject* nodeObject);
      /// Called when segment visibility is changed from the segment combobox
      void onSegmentVisibilitySelectionChanged(QStringList selectedSegmentIDs);
      /// Update segmentation outline/fill button
      void updateSegmentationOutlineFillButton();
      /// Utility function to get the display node of the current segmentation
      vtkMRMLSegmentationDisplayNode* currentSegmentationDisplayNode();
      void updateFromForegroundDisplayNode(vtkObject* displayNode);
      void updateFromBackgroundDisplayNode(vtkObject* displayNode);
      void updateFromForegroundVolumeNode(vtkObject* volumeNode);
      void updateFromBackgroundVolumeNode(vtkObject* volumeNode);
      /// Called after the SliceLogic is modified
      void onSliceLogicModifiedEvent();
      void applyCustomLightbox();
      void setupPopupUi() override;
      virtual void setMRMLSliceNodeInternal(vtkMRMLSliceNode* sliceNode);
      void setMRMLSliceCompositeNodeInternal(vtkMRMLSliceCompositeNode* sliceComposite);
      vtkMRMLSliceNode*                   MRMLSliceNode;
      vtkMRMLSliceCompositeNode*          MRMLSliceCompositeNode;
      vtkSmartPointer<vtkMRMLSliceLogic>  SliceLogic;
      vtkCollection*                      SliceLogics;
      vtkWeakPointer<vtkAlgorithmOutput>  ImageDataConnection;
      QHash<QString, qMRMLOrientation>    SliceOrientationToDescription;
      QString                             SliceViewName;
      QButtonGroup*                       ControllerButtonGroup;
      QToolButton*                        FitToWindowToolButton;
      qMRMLSliderWidget*                  SliceOffsetSlider;
     ctkDoubleSpinBox*                   spinBox;
      double                              LastLabelMapOpacity;
      double                              LastForegroundOpacity;
      double                              LastBackgroundOpacity;
      QMenu*                              LightboxMenu;
      QMenu*                              CompositingMenu;
      QMenu*                              SliceSpacingMenu;
      QMenu*                              SliceModelMenu;
      QMenu*                              SegmentationMenu;
      QMenu*                              LabelMapMenu;
      QMenu*                              OrientationMarkerMenu;
      QMenu*                              RulerMenu;
      ctkDoubleSpinBox*                   SliceSpacingSpinBox;
      ctkDoubleSpinBox*                   SliceFOVSpinBox;
      QSpinBox*                           LightBoxRowsSpinBox;
      QSpinBox*                           LightBoxColumnsSpinBox;
      ctkDoubleSpinBox*                   SliceModelFOVXSpinBox;
      ctkDoubleSpinBox*                   SliceModelFOVYSpinBox;
      ctkDoubleSpinBox*                   SliceModelOriginXSpinBox;
      ctkDoubleSpinBox*                   SliceModelOriginYSpinBox;
      QSpinBox*                           SliceModelDimensionXSpinBox;
      QSpinBox*                           SliceModelDimensionYSpinBox;
      QSize                               ViewSize;
      ctkSignalMapper*                    OrientationMarkerTypesMapper;
      ctkSignalMapper*                    OrientationMarkerSizesMapper;
      ctkSignalMapper*                    RulerTypesMapper;
      ctkSignalMapper*                    RulerColorMapper;

  • qMRMLSliceControllerWidget.cxx:

    void qMRMLSliceControllerWidgetPrivate::init()
      this->FitToWindowToolButton = new QToolButton(q);
      //this->FitToWindowToolButton->setToolTip(tr("Adjust the Slice Viewer's field of view to match the extent of lowest non-None volume layer (bg, then fg, then label)."));
      //QIcon fitToWindowIcon(":/Icons/SlicesFitToWindow.png");
      this->FitToWindowToolButton->setFixedSize(15, 15);
      this->BarLayout->insertWidget(2, this->FitToWindowToolButton);
      //Hide FitToWindowToolButton from the Barlayout
      this->SliceOffsetSlider = new qMRMLSliderWidget(q);
      this->SliceOffsetSlider->setToolTip(qMRMLSliceControllerWidget::tr("Slice distance from RAS origin"));
        ctkDoubleSpinBox::DecimalsByShortcuts |
        ctkDoubleSpinBox::DecimalsByKey |
        ctkDoubleSpinBox::DecimalsAsMin );
      spinBox = this->SliceOffsetSlider->spinBox();
      spinBox->setSizePolicy(QSizePolicy::Minimum, QSizePolicy::Minimum);
      int targetHeight = spinBox->parentWidget()->layout()->sizeHint().height();//setSizeConstraint(QLayout::SetMinimumSize);
      int fontHeight = spinBox->fontMetrics().height();
      qreal heightRatio = static_cast<qreal>(targetHeight - 2) / fontHeight;
      if (heightRatio  < 1.)
        QFont stretchedFont(spinBox->font());
        stretchedFont.setPointSizeF(stretchedFont.pointSizeF() * heightRatio);
      // Connect Slice offset slider
      this->connect(this->SliceOffsetSlider, SIGNAL(valueChanged(double)),
                    q, SLOT(setSliceOffsetValue(double)), Qt::QueuedConnection);
      this->connect(this->SliceOffsetSlider, SIGNAL(valueIsChanging(double)),
                    q, SLOT(trackSliceOffsetValue(double)), Qt::QueuedConnection);
      this->connect(q, SIGNAL(mrmlSceneChanged(vtkMRMLScene*)),
                    this->SliceOffsetSlider, SLOT(setMRMLScene(vtkMRMLScene*)));
      // Move the spinbox in the popup instead of having it in the slider bar
      //  this->SliceOffsetSlider->spinBox(), 0, 0, 1, 2);
      // Hide all buttons by default
      vtkNew<vtkMRMLSliceLogic> defaultLogic;

    i want to use this spinBox in qMRMLSliceWidget

  • and the qMRMLSliceControllerWidget constructor is

    qMRMLSliceControllerWidgetPrivate::qMRMLSliceControllerWidgetPrivate(qMRMLSliceControllerWidget& object)
      : Superclass(object)
      this->SliceLogic = nullptr;
      this->MRMLSliceNode = nullptr;
      this->MRMLSliceCompositeNode = nullptr;
      this->SliceLogics = nullptr;
      this->ControllerButtonGroup = nullptr;
      qMRMLOrientation axialOrientation = {qMRMLSliceControllerWidget::tr("Axial:"), qMRMLSliceControllerWidget::tr("I <-----> S")};
      qMRMLOrientation sagittalOrientation = {qMRMLSliceControllerWidget::tr("Sagittal:"), qMRMLSliceControllerWidget::tr("L <-----> R")};
      qMRMLOrientation coronalOrientation = {qMRMLSliceControllerWidget::tr("Coronal:"), qMRMLSliceControllerWidget::tr("P <-----> A")};
      qMRMLOrientation obliqueOrientation = {"", qMRMLSliceControllerWidget::tr("Oblique")};
      this->SliceOrientationToDescription["Axial"] = axialOrientation;
      this->SliceOrientationToDescription["Sagittal"] = sagittalOrientation;
      this->SliceOrientationToDescription["Coronal"] = coronalOrientation;
      this->SliceOrientationToDescription["Reformat"] = obliqueOrientation;
      this->LastLabelMapOpacity = 1.;
      this->LastForegroundOpacity = 1.;
      this->LastBackgroundOpacity = 1.;
      this->FitToWindowToolButton = nullptr;
      this->SliceOffsetSlider = nullptr;
      this->spinBox = nullptr;
      this->LightboxMenu = nullptr;
      this->CompositingMenu = nullptr;
      this->SliceSpacingMenu = nullptr;
      this->SliceModelMenu = nullptr;
      this->SegmentationMenu = nullptr;
      this->LabelMapMenu = nullptr;
      this->OrientationMarkerMenu = nullptr;
      this->RulerMenu = nullptr;
      this->SliceSpacingSpinBox = nullptr;
      this->SliceFOVSpinBox = nullptr;
      this->LightBoxRowsSpinBox = nullptr;
      this->LightBoxColumnsSpinBox = nullptr;
      this->SliceModelFOVXSpinBox = nullptr;
      this->SliceModelFOVYSpinBox = nullptr;
      this->SliceModelOriginXSpinBox = nullptr;
      this->SliceModelOriginYSpinBox = nullptr;
      this->SliceModelDimensionXSpinBox = nullptr;
      this->SliceModelDimensionYSpinBox = nullptr;

    i want to place this spinBox in qMRMLSliceWidget, is there any method for doing this?

  • Lifetime Qt Champion

    Do you mean its
    ctkDoubleSpinBox* spinBox; ?

    well its public so i guess you can.

    it sems to be allocated / assigned in
    spinBox = this->SliceOffsetSlider->spinBox();

    but im still not sure what that "q" is that it seems to use for constructor.

  • I Have a QToolButton in the first UI I don't want to display it over there but the functionalities/actions of the button are initialized in the first.cxx file. So when I create an object of the first class in the second class and try adding the button in a widget of the second class does the button get transferred?

    QToolButton code in qMRMLSLiceControllerWidget.cxx:

    this->FitToWindowToolButton = new QToolButton(q);
    this->FitToWindowToolButton->setFixedSize(15, 15);
    QObject::connect(this->actionFit_to_window, SIGNAL(triggered()),
                   q, SLOT(fitSliceToBackground()));

    Object of qMRMLSLiceControllerWidget in qMRMLSliceWidget: initialization in qMRMLSliceWidget_p.h:

    qMRMLSliceControllerWidget* scw;

    declaration in qMRMLSliceWidget.cxx:

    scw = new qMRMLSliceControllerWidget(q);

    when I create an object like this in my App I don't know for what reason 0.00 is getting displayed
    Screenshot (312).png

  • Thank you and everyone, I also had the same problem.

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