学习QT的第六天

飞舞的蝴蝶

代码结构：

butterfly.h

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

class Butterfly : public QObject,public QGraphicsItem
{
    Q_OBJECT
public:
    explicit Butterfly(QObject *parent = 0);
    void timerEvent(QTimerEvent *);				//定时器
    QRectF boundingRect() const;				//为图元限定范围
signals:
public slots:
protected:
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);								//重绘函数
private:
    bool up;						//
    QPixmap pix_up;      				//用于表示两幅蝴蝶的图片
    QPixmap pix_down;
    qreal angle;
};

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();
};

#endif // MAINWINDOW_H

butterfly.cpp

#include "butterfly.h"
#include <math.h>
const static double PI=3.1416;

Butterfly::Butterfly(QObject *parent) : QObject(parent)
{
    up = true;				//给标志蝴蝶翅膀位置的变量赋初值
    pix_up.load("up.jpg");			//调用QPixmap的load()函数加载所用到的图片
    pix_down.load("down.jpg");
    startTimer(100);				//启动定时器，并设置时间间隔为100毫秒
}


QRectF Butterfly::boundingRect() const
{
    qreal adjust=2;
    return QRectF(-pix_up.width()/2-adjust,-pix_up.height()/2-adjust,
                  pix_up.width()+adjust*2,pix_up.height()+adjust*2);

}


void Butterfly::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    if(up)
    {
        painter->drawPixmap(boundingRect().topLeft(),pix_up);
        up=!up;
    }
    else
    {
        painter->drawPixmap(boundingRect().topLeft(),pix_down);
        up=!up;
    }
}

void Butterfly::timerEvent(QTimerEvent *)
{
    //边界控制
    qreal edgex=scene()->sceneRect().right()+boundingRect().width()/2;
    qreal edgetop=scene()->sceneRect().top()+boundingRect().height()/2;
    qreal edgebottom=scene()->sceneRect().bottom()+boundingRect().height()/2;
    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());
    angle+=(qrand()%10)/20.0;
    qreal dx=fabs(sin(angle*PI)*10.0);
    qreal dy=(qrand()%20)-10.0;
    setPos(mapToParent(dx,dy));
}

mainwindow.cpp

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();
};

#endif // MAINWINDOW_H

mian.cpp

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

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QGraphicsScene *scene=new QGraphicsScene;
    scene->setSceneRect(QRectF(-200,-200,400,400));
    Butterfly *butterfly =new Butterfly;
    butterfly->setPos(-100,0);
    scene->addItem(butterfly);
    QGraphicsView *view=new QGraphicsView;
    view->setScene(scene);
    view->resize(400,400);
    view->show();

    return a.exec();
}