从MainWindow调用时，QGraphicsScene未显示在QDockWidget的QGraphicsView中

Question

我在QDockWidget中有一个QGraphicsView，我在其中显示一个PNG图像。如果我在dockwidget的构造函数中创建一个QPixMapItem，并从构造函数中调用dockwidgets的成员函数(一个公共槽(来显示图像，它就可以正常工作。

但是，如果我通过信号从MainWindow(一个名为"IView"的类(调用插槽，则图像不会显示。我做错了什么？

Dockwidget构造：

IvConfDockWidget::IvConfDockWidget(IView *parent) :
QDockWidget(parent),
ui(new Ui::IvConfDockWidget)
{
ui->setupUi(this);
MyGraphicsView *zoomGraphicsView = new MyGraphicsView();
MyGraphicsScene *zoomScene = new MyGraphicsScene();
ui->zoomLayout->addWidget(zoomGraphicsView);
QPixmap zoomPixmap = QPixmap("/home/mischa/logo.png");
QGraphicsPixmapItem *zoomPixmapItem = new QGraphicsPixmapItem(zoomPixmap);
updateZoomWindowReceived(zoomPixmapItem);       // does not work if called from MainWindow
}

这是公用插槽：

void IvConfDockWidget::updateZoomWindowReceived(QGraphicsPixmapItem *zoomPixmapItem)
{
zoomGraphicsView->resetMatrix();
zoomScene->clear();
zoomScene->addItem(zoomPixmapItem);
zoomGraphicsView->setScene(zoomScene);
zoomGraphicsView->show();
}

如果我在构造函数中注释掉updateZoomWindowReceived()，并通过MainWindow中的信号调用它，那么图形就不会显示。这是我的主窗口中的代码：

IvConfDockWidget *icdw = new IvConfDockWidget;
connect(this, &IView::updateZoomWindow, icdw, &IvConfDockWidget::updateZoomWindowReceived);
QPixmap zoomPixmap = QPixmap("/home/mischa/logo.png");
icdw->zoomGraphicsView->resetMatrix();
QGraphicsPixmapItem *newItem = new QGraphicsPixmapItem(zoomPixmap);
emit updateZoomWindow(newItem);

为了完整起见，我的QGraphicsView和QGraphicsScene:的派生版本

#define MYGRAPHICSVIEW_H
#include <QGraphicsView>
#include <QDebug>
#include <QMouseEvent>
#include <QScrollBar>
class MyGraphicsView : public QGraphicsView
{
Q_OBJECT
private:
QPointF rightDragStartPos;
QPointF rightDragCurrentPos;
QPointF rightDragEndPos;
QPointF leftDragStartPos;
QPointF leftDragCurrentPos;
QPointF leftDragEndPos;        // unused
QPointF middleDragStartPos;
QPointF middleDragCurrentPos;
QPointF middleDragEndPos;
bool rightButtonPressed = false;
bool leftButtonPressed = false;
bool middleButtonPressed = false;
QPoint previousMousePoint;
bool _pan = false;
int _panStartX = 0;
int _panStartY = 0;
public:
explicit MyGraphicsView();
void mouseMoveEvent(QMouseEvent *event);
void mousePressEvent(QMouseEvent *event);
void mouseReleaseEvent(QMouseEvent *event);
QScrollBar *sxbar = nullptr;
QScrollBar *sybar = nullptr;
QString middleMouseMode = "DragMode";
int x = 0;
int y = 0;
signals:
void currentMousePos(QPointF);
void rightDragTravelled(QPointF);
void middleDragTravelled(QPointF pointStart, QPointF pointEnd);
void middleWCSTravelled(QPointF pointStart, QPointF pointEnd);
void middleWCSreleased();
void leftDragTravelled(QPointF pointStart, QPointF pointEnd);
void rightPress();
void leftPress(QPointF pointStart);
void middlePress(QPointF point);
void leftButtonReleased();
void rightButtonReleased();
void middleButtonReleased();
void middlePressResetCRPIX();
public slots:
void updateMiddleMouseMode(QString mode);
};
#endif // MYGRAPHICSVIEW_H

和

#ifndef MYGRAPHICSSCENE_H
#define MYGRAPHICSSCENE_H
#include <QObject>
#include <QGraphicsScene>
#include <QKeyEvent>
class MyGraphicsScene : public QGraphicsScene
{
Q_OBJECT
public:
MyGraphicsScene();
signals:
void itemDeleted();
protected:
void keyReleaseEvent(QKeyEvent * keyEvent);
};
#endif // MYGRAPHICSSCENE_H

Answer 1

我想明白了。我的MainWindow使用了一个混合驱动器/RAM数据模型，它可以处于不同的状态，碰巧在其中一个状态下从未发出信号。一旦我解决了这个问题，行为就如所愿。

抱歉有噪音。