Qt：飞舞的蝴蝶

我不是女神ヾ 2023-01-12 11:45 199阅读 0赞

1、新建Qt GUI应用，基类QMainWindows，取消创建界面

2、项目名称上选择“添加新文件”--->"C++类"-->基类“QObject”,类名"Butterfly"

3、butterfly.h

#ifndef BUTTERFLY_H
    #define 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 = nullptr);
        void timerEvent(QTimerEvent *);
        QRectF boundingRect() const;
    
    signals:
    
    public slots:
    
    protected:
        void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
    
    private:
        bool up;
        QPixmap pix_up;            //用于表示两幅蝴蝶的图片
        QPixmap pix_down;
    
        qreal angle;
    };
    
    #endif // BUTTERFLY_H

butterfly.cpp

#include "butterfly.h"
    #include <math.h>
    
    const static double PI=3.1416;
    
    Butterfly::Butterfly(QObject *parent) :
        QObject(parent)
    {
        up = true;
        pix_up.load("F:\\MyCode\\Butterfly\\up.png");
        pix_down.load("F:\\MyCode\\Butterfly\\down.png");
    
        startTimer(100);
    }
    
    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));
    }

main.cpp

#include "mainwindow.h"
    #include <QApplication>
    #include <QGraphicsScene>
    #include <QGraphicsItem>
    #include "butterfly.h"
    
    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;
    
        scene->addItem(butterfly);
    
        QGraphicsView *view = new QGraphicsView(scene);
        view->resize(400, 400);
        view->show();
    
        return a.exec();
    }

4、分析：重新实现bounding&painter，在timerEvent中设置边界

![8c842745cde96908c949e2f328fcf69c.png][]

[8c842745cde96908c949e2f328fcf69c.png]: /images/20221119/7991524d7e4f46f28a9ee9a88aa81e7d.png