QGraphicsView,QGraphicsScene,QGraphicsItem

参考：Qt4 开发实践第八章 图形视图QGraphicsView

#ifndef DRIVEDGRAPH_H
#define DRIVEDGRAPH_H

#include <QObject>
#include <QGraphicsItem>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QPainter>

class DrivedGraph : public QObject,public QGraphicsItem
{
    Q_OBJECT
public:
    DrivedGraph();
    void timerEvent(QTimerEvent *); // 在定时器里对QGraphicsItem 进行重画
    QRectF boundingRect() const;    // 为图元限定区域范围，所有继承自QGraphicsItem的自定义图元都必须实现此函数
protected:
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget); // 重画函数,继承自QGraphicsItem
private:
    bool m_bupFlag;
    QPixmap m_pixUp;
    QPixmap m_pixDown;
    qreal m_angle;
};

#endif // DRIVEDGRAPH_H

#include "drivedgraph.h"
#include <math.h>
#include <QDebug>

const static double PI = 3.1416;

DrivedGraph::DrivedGraph()
{
    m_bupFlag = true;
    m_pixUp = QPixmap(":/Image/up.png");
    m_pixDown = QPixmap(":/Image/down.png");
    startTimer();
}

void DrivedGraph::timerEvent(QTimerEvent *)
{
    qreal edgex = scene()->sceneRect().right() + boundingRect().width()/;  // 限定右边界
    qreal edgetop = scene()->sceneRect().top() + boundingRect().height()/; // 上边界
    qreal edgebottom = scene()->sceneRect().bottom() + boundingRect().height()/;   // 下边界

    qDebug() << "edgex: " << edgex << "edgetop: " << edgetop << "edgebottom: " << edgebottom;

    if (pos().x() >= edgex) {
        setPos(scene()->sceneRect().left(),pos().y());
    }
    if (pos().y() <= edgetop) {
        setPos(pos().x(),scene()->sceneRect().bottom());
    }
    if (pos().y() >= edgebottom) {
        setPos(pos().x(),scene()->sceneRect().top());
    }

    qDebug() << "pos().x(): " << pos().x() << "pos().y(): " << pos().y() ;

    m_angle += (qrand()%) / 20.0;
    qreal dx = fabs(sin(m_angle*PI)*10.0);
    qreal dy = (qrand()%) - 10.0;
    setPos(mapToParent(dx,dy));
}

QRectF DrivedGraph::boundingRect() const
{
    qreal adjust = ;
    return QRectF(-m_pixUp.width()/ - adjust,-m_pixUp.height()/ - adjust,
                  m_pixUp.width() + adjust*,m_pixUp.height() + adjust*);
}

void DrivedGraph::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    if (m_bupFlag) {
        painter->drawPixmap(boundingRect().topLeft(),m_pixUp);
        m_bupFlag = !m_bupFlag;
    }
    else {
        painter->drawPixmap(boundingRect().topLeft(),m_pixDown);
        m_bupFlag = !m_bupFlag;
    }
}

实现蝴蝶飞舞

#include "butterfly.h"
#include <QApplication>

#include "drivedgraph.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
//    Butterfly w;
//    w.show();

    QGraphicsScene *scene = new QGraphicsScene;
    scene->setSceneRect(QRectF(-,-,,));
    DrivedGraph *dri = new DrivedGraph;
    dri->setPos(-,);
    scene->addItem(dri);

    QGraphicsView *view = new QGraphicsView;
    view->setScene(scene);
    view->resize(,);
    view->show();

    return a.exec();
}