这次基本上没出大的错误。。根据按键向下的功能实现了一下向上的功能，还有旋转rotate()功能

myitem.h

#ifndef MYITEM_H
#define MYITEM_H

#include <QGraphicsItem>

class myItem : public QGraphicsItem
{
public:
    myItem();
    QRectF boundingRect() const;
    void paint(QPainter *painter,const QStyleOptionGraphicsItem *option,
               QWidget *widget);
    void setColor(const QColor &color){brushColor = color;}
    void keyPressEvent(QKeyEvent *event);
    void mousePressEvent(QGraphicsSceneMouseEvent *event); //鼠标按键响应
    void hoverEnterEvent(QGraphicsSceneHoverEvent *event);  //停留显示
    void contextMenuEvent(QGraphicsSceneContextMenuEvent *event); 
private:
    QColor brushColor;
};

#endif // MYITEM_H

#ifndef MYVIEW_H
#define MYVIEW_H

#include <QGraphicsView>

class MyView : public QGraphicsView
{
    Q_OBJECT
public:
    explicit MyView(QWidget *parent = 0);
protected:
    void keyPressEvent(QKeyEvent *event);
signals:

public slots:

};

#endif // MYVIEW_H

#include <QApplication>
#include "myitem.h"
#include "myview.h"
#include "myitem.cpp"
#include "myview.cpp"
#include <QTime>

int main(int argc,char *argv[])
{
    QApplication app(argc,argv);
    qsrand(QTime(0,0,0).secsTo(QTime::currentTime()));
    QGraphicsScene scene;
    scene.setSceneRect(-200,-150,400,300);
    for(int i = 0;i <= 5;++i)
    {
        myItem *item = new myItem;
        item->setColor(QColor(qrand() % 256,qrand() % 256,qrand() % 256)); //随机生成颜色
        item->setPos(i * 50 - 90, -50);
        scene.addItem(item);
    }
    MyView view;
    view.setScene(&scene);
    view.setBackgroundBrush(QPixmap("../myView/11.jpg"));
    view.show();
    return app.exec();
}

#include "myitem.h"
#include <QPainter>
#include <QCursor>
#include <QKeyEvent>
#include <QGraphicsSceneHoverEvent>
#include <QGraphicsSceneContextMenuEvent>
#include <QMenu>

myItem::myItem()
{
    brushColor = Qt::red;
    setFlag(QGraphicsItem::ItemIsFocusable);
    setFlag(QGraphicsPathItem::ItemIsMovable);
    setAcceptHoverEvents(true);
}
QRectF myItem::boundingRect() const
{
    qreal adjust = 0.5;
    return QRectF(-10 - adjust,-10 - adjust,
                  20 + adjust,20 + adjust);
}
void myItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    if(hasFocus())
    {
        painter->setPen(QPen(QColor(255,255,255,200)));
    } else {
        painter->setPen(QPen(QColor(100,100,100,100)));
    }
    painter->setBrush(brushColor);
    painter->drawRect(-10,-10,20,20);

}
void myItem::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
    setFocus();
    setCursor(Qt::ClosedHandCursor);
}
void myItem::keyPressEvent(QKeyEvent *event)
{
    if(event->key() == Qt::Key_Down) //x,y对应移动
    {
        moveBy(0,10);
    }
    else if(event->key() == Qt::Key_Up)
    {
        moveBy(0,-10);
    }
}
void myItem::hoverEnterEvent(QGraphicsSceneHoverEvent *event)
{
    setCursor(Qt::OpenHandCursor);
    setToolTip("I am item");
}
void myItem::contextMenuEvent(QGraphicsSceneContextMenuEvent *event)
{
    QMenu menu;
    QAction *moveAction = menu.addAction("move back"); //右键显示菜单
    QAction *selectedAction = menu.exec(event->screenPos());
    if(selectedAction == moveAction) //回到（0,0）点
    {
        setPos(0,0);
    }
}

#include "myview.h"
#include <QKeyEvent>

MyView::MyView(QWidget *parent) :
    QGraphicsView(parent)
{
}
void MyView::keyPressEvent(QKeyEvent *event)
{
    switch (event->key()) {
    case Qt::Key_Plus: //+号
        scale(1.2,1.2);
        break;
    case Qt::Key_Minus: //-号
        scale(1/1.2,1/1.2);
        break;
    case Qt::Key_Right:
        rotate(30);
        break;
    case Qt::Key_Left:
        rotate(-30);
        break;
    }
    QGraphicsView::keyPressEvent(event);
}