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(30);
  }
  
  //图元的边界区域
  QRectF fly::boundingRect() const
  {
      qreal angletemp = 2;
      return QRectF(-pix_up.width()/2-angletemp,
                    -pix_up.height()/2-angletemp,
                    pix_up.width()+angletemp*2,
                    pix_up.height()+angletemp*2);
  }
  
  //定时器函数
  void fly::timerEvent(QTimerEvent *event)
  {
      //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());
  
  #define PI 3.14
      angle += (qrand() % 10)/20.0;
      qreal dx = fabs(sin(angle*PI)*10);
      qreal dy = (qrand()%20)-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(-300,-200,400,500);
  
      fly *f = new fly;
      f->setPos(-100,0);
      scene->addItem(f);
  
      QGraphicsView *view = new QGraphicsView;
      view->setScene(scene);
      view->resize(800,600);
      view->show();
  
      return a.exec();
  }