35.QT蝴蝶飞舞

• fly.h

   #ifndef FLY_H
   #define FLY_H
   #include <QObject>
   #include <QPainter>
   #include <QGraphicsScene>
   #include <QGraphicsView>
   #include <QGraphicsItem>
   #include <QPixmap>
   #include <math.h>
   #include <QTime>
   #include <QEvent>
  
   //图元对象
   class fly : public QObject,public QGraphicsItem
   {
       Q_OBJECT
   public:
       explicit fly(QObject *parent = nullptr);
  
       //区域
       QRectF boundingRect() const;
       //时间定时器
       void timerEvent(QTimerEvent *event);
   signals:
  
   public slots:
  
   protected:
       //绘制
       void paint(QPainter *painter,const QStyleOptionGraphicsItem *option,QWidget *widget);
  
   public:
       bool up;
       QPixmap pix_up;
       QPixmap pix_down;
  
       qreal angle;
  
   };
  
   #endif // FLY_H

• fly.cpp

   #include "fly.h"
  
   fly::fly(QObject *parent) : QObject(parent)
   {
       //载入
       up = true;
       pix_up.load("up.png");
       pix_down.load("down.png");
  
       startTimer();
   }
  
   //图元的边界区域
   QRectF fly::boundingRect() const
   {
       qreal angletemp = ;
       return QRectF(-pix_up.width()/-angletemp,
                     -pix_up.height()/-angletemp,
                     pix_up.width()+angletemp*,
                     pix_up.height()+angletemp*);
   }
  
   //定时器函数
   void fly::timerEvent(QTimerEvent *event)
   {
       //边界控制
       qreal edgex = scene()->sceneRect().right()+boundingRect().width()/;
       qreal edgetop=scene()->sceneRect().top()+boundingRect().height()/;
       qreal edgebottom = scene()->sceneRect().bottom()+boundingRect().height()/;
  
       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());
  
   #define PI 3.14
       angle += (qrand() % )/20.0;
       qreal dx = fabs(sin(angle*PI)*);
       qreal dy = (qrand()%)-10.0;
  
       //设置位置,转换坐标
       setPos(mapToParent(dx,dy));
   }
  
   void fly::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;
       }
   }

• main.cpp

   #include "dialog.h"
   #include <QApplication>
   #include <QGraphicsScene>
   #include <QGraphicsView>
   #include "fly.h"
  
   int main(int argc, char *argv[])
   {
       QApplication a(argc, argv);
  
       //创建图像场景
       QGraphicsScene *scene = new QGraphicsScene;
       //设置区域
       scene->setSceneRect(-,-,,);
  
       fly *f = new fly;
       f->setPos(-,);
       scene->addItem(f);
  
       QGraphicsView *view = new QGraphicsView;
       view->setScene(scene);
       view->resize(,);
       view->show();
  
       return a.exec();
   }