移动QGraphicsScene？

Question

如何在视图中移动QGraphicsscene？

我有一个场景填充整个视图。场景包含一个（稍后会有）项目（现在为QImage），每隔几秒更新一次。

我的目标是使用mouseMoveEvent移动项目的内容。当项目更新（持续几秒钟）时，我想移动整个场景并在项目完全更新后重置移动。

现在我尝试重写QGraphicsScene的mouseMoveEvent并向PPI-Class发出一个包含QGraphicsScene Objet的信号。然后onMouseMoveEvent-slot尝试设置sceneRect。但这不起作用，我得到一个StackOverflow-Exception。

我怎样才能让它发挥作用？谢谢！

的main.cpp

#include "ppi.h"
#include <QtGui/QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    PPI w;
    w.show();
    return a.exec();
}

ppi.ui（刚刚添加了一个大小为1024x1024的图形视图，并将gVPPI命名为主窗口）

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>PPIClass</class>
 <widget class="QMainWindow" name="PPIClass">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>1079</width>
    <height>1113</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>PPI</string>
  </property>
  <widget class="QWidget" name="centralWidget">
   <widget class="QGraphicsView" name="gVPPI">
    <property name="geometry">
     <rect>
      <x>10</x>
      <y>10</y>
      <width>1024</width>
      <height>1024</height>
     </rect>
    </property>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menuBar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>1079</width>
     <height>21</height>
    </rect>
   </property>
  </widget>
  <widget class="QToolBar" name="mainToolBar">
   <attribute name="toolBarArea">
    <enum>TopToolBarArea</enum>
   </attribute>
   <attribute name="toolBarBreak">
    <bool>false</bool>
   </attribute>
  </widget>
  <widget class="QStatusBar" name="statusBar"/>
 </widget>
 <layoutdefault spacing="6" margin="11"/>
 <resources>
  <include location="ppi.qrc"/>
 </resources>
 <connections/>
</ui>

ppi.h

#ifndef PPI_H
#define PPI_H

#include <QtGui/QMainWindow>
#include "ui_ppi.h"
#include "ppiscene.h"

#include <QGraphicsView>
#include <QGraphicsPixmapItem>
#include <QDebug>

class PPI : public QMainWindow
{
    Q_OBJECT

public:
    PPI(QWidget *parent = 0, Qt::WFlags flags = 0);
    ~PPI();

private:
    Ui::PPIClass ui;
    PPIScene* ppiScene;
    QGraphicsPixmapItem *videoPixmap;

    QImage newImage();

    bool moveReset;

    QPointF moveCoordinates;
    QPointF startMoveCoordinates;

protected slots:
    void onMouseMoved(QPointF coordinates, QGraphicsSceneMouseEvent *event);
};

#endif // PPI_H

ppi.cpp

#include "ppi.h"


PPI::PPI(QWidget *parent, Qt::WFlags flags)
    : QMainWindow(parent, flags)
{
    ui.setupUi(this);

    ppiScene = new PPIScene(this);
    ppiScene->setSceneRect(0,0,1024,1024);
    ui.gVPPI->setScene(ppiScene);
    ui.gVPPI->setMouseTracking(true);

    videoPixmap = ppiScene->addPixmap(QPixmap::fromImage(newImage()));

        startMoveCoordinates = QPointF(0,0);

    connect(ppiScene, SIGNAL(mouseMoved(QPointF, QGraphicsSceneMouseEvent*)), this, SLOT(onMouseMoved(QPointF, QGraphicsSceneMouseEvent*)));
}

PPI::~PPI()
{

}

void PPI::onMouseMoved(QPointF coordinates, QGraphicsSceneMouseEvent *event)
{
    //move view
    if(event->modifiers() & Qt::ControlModifier)
    {
        moveCoordinates = coordinates;
        //ui.gVPPI->translate(moveCoordinates.x() - startMoveCoordinates.x(), moveCoordinates.y() - startMoveCoordinates.y());
        ppiScene->setSceneRect(moveCoordinates.x() - startMoveCoordinates.x(), moveCoordinates.y() - startMoveCoordinates.y(), 1024, 1024);
        qDebug() << coordinates;
        qDebug() << "dx" << moveCoordinates.x() - startMoveCoordinates.x();
        qDebug() << "dy" << moveCoordinates.y() - startMoveCoordinates.y();
        qDebug() << "";
    }
}

QImage PPI::newImage() {

    QImage image = QImage(1024, 1024, QImage::Format_Indexed8);
  image.setColorCount(256);

  for (int i = 0; i < 256; ++i)
    image.setColor(i, qRgb(i, 0, 0));
  image.fill(200);
  return image;
}

ppiscene.h

#ifndef PPISCENE_H
#define PPISCENE_H

#include <QGraphicsScene>
#include <QGraphicsSceneMouseEvent>

class PPIScene : public QGraphicsScene
{
    Q_OBJECT

public:
    PPIScene(QObject *parent);
    ~PPIScene();
    QPointF mouseCoordinates;

private:

protected:
    void mouseMoveEvent(QGraphicsSceneMouseEvent *event);

signals:
    void mouseMoved(QPointF coordinates, QGraphicsSceneMouseEvent *event);

};

#endif // PPISCENE_H

ppiscene.cpp

#include "ppiscene.h"

PPIScene::PPIScene(QObject *parent)
    : QGraphicsScene(parent)
{

}

PPIScene::~PPIScene()
{

}

void PPIScene::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
    mouseCoordinates = event->scenePos();
    emit mouseMoved(mouseCoordinates, event);
    QGraphicsScene::mouseMoveEvent(event);
}