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();

}