Qt学习笔记-图像碰撞（变色，消失，跟随）

运行截图如下：
红色：圆矩形我们控制的
蓝色：圆矩形（碰撞变色）
绿色：圆形（碰撞后消失）

黑色：矩形（碰撞后跟随）

代码如下：

graphicsitem.h

#ifndef GRAPHICSITEM_H
#define GRAPHICSITEM_H

#include <QGraphicsItem>

class GraphicsItem:public QGraphicsItem
{
public:
    GraphicsItem();
    QRectF boundingRect()const;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
    void setColor(const QColor &color);

protected:
    void mousePressEvent(QGraphicsSceneMouseEvent *event);
    void keyPressEvent(QKeyEvent *event);

private:
    QColor m_color;
};

#endif // GRAPHICSITEM_H

graphicsitem2.h

#ifndef GRAPHICSITEM2_H
#define GRAPHICSITEM2_H

#include <QGraphicsItem>


class GraphicsItem2:public QGraphicsItem
{
public:
    GraphicsItem2();
    QRectF boundingRect()const;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
    void setColor(const QColor &color);
    void setMyFlag(int flag);
    int getMyFlag();

    void reflush();

    void ChangeRang();

protected:
    void mousePressEvent(QGraphicsSceneMouseEvent *event);

private:
    QColor m_color;
    int m_flag;


};

#endif // GRAPHICSITEM2_H

graphicsitem.cpp

#include "graphicsitem.h"
#include "graphicsitem2.h"
#include "graphicsflag.h"

#include <QPainter>
#include <QCursor>
#include <QKeyEvent>
#include <QGraphicsView>
#include <QDebug>
#include <typeinfo>

GraphicsItem::GraphicsItem()
{
    m_color=Qt::black;
    setFlag(QGraphicsItem::ItemIsFocusable);
    setFlag(QGraphicsItem::ItemIsMovable);
}

QRectF GraphicsItem::boundingRect()const{
    qreal penWidth=1;
    return QRectF(0-penWidth/2,0-penWidth/2,100+penWidth,100+penWidth);
}

void GraphicsItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget){
    Q_UNUSED(option)
    Q_UNUSED(widget)
    painter->setBrush(m_color);
    painter->drawRoundedRect(0,0,100,100,5,5);
}

void GraphicsItem::setColor(const QColor &color){
    m_color=color;
}


void GraphicsItem::mousePressEvent(QGraphicsSceneMouseEvent *event){
    Q_UNUSED(event)
    setFocus();
    setCursor(Qt::ClosedHandCursor);
}

void GraphicsItem::keyPressEvent(QKeyEvent *event){
    if(event->key()==Qt::Key_Down)
        moveBy(0,10);
    else if(event->key()==Qt::Key_Up)
        moveBy(0,-10);
    else if(event->key()==Qt::Key_Left)
        moveBy(-10,0);
    else if(event->key()==Qt::Key_Right)
        moveBy(10,0);

    QList<QGraphicsItem*>list=collidingItems();
    if(!list.isEmpty()){
        if(QString(typeid(*(list.at(0))).name())=="13GraphicsItem2"){
            if(((GraphicsItem2 *)(list.at(0)))->getMyFlag()==1){
                ((GraphicsItem2 *)(list.at(0)))->setColor(Qt::yellow);
                ((GraphicsItem2 *)(list.at(0)))->reflush();
                ((GraphicsItem2 *)(list.at(0)))->setMyFlag(2);
            }
            else if(((GraphicsItem2 *)(list.at(0)))->getMyFlag()==2){
                ((GraphicsItem2 *)(list.at(0)))->setColor(Qt::blue);
                ((GraphicsItem2 *)(list.at(0)))->reflush();
                ((GraphicsItem2 *)(list.at(0)))->setMyFlag(1);
            }
            else if(((GraphicsItem2 *)(list.at(0)))->getMyFlag()==3){
                ((GraphicsItem2 *)(list.at(0)))->hide();
            }
            else{
                if(event->key()==Qt::Key_Down)
                    ((GraphicsItem2 *)(list.at(0)))->moveBy(0,10);
                else if(event->key()==Qt::Key_Up)
                    ((GraphicsItem2 *)(list.at(0)))->moveBy(0,-10);
                else if(event->key()==Qt::Key_Left)
                    ((GraphicsItem2 *)(list.at(0)))->moveBy(-10,0);
                else if(event->key()==Qt::Key_Right)
                    ((GraphicsItem2 *)(list.at(0)))->moveBy(10,0);
            }
        }
    }
    list.clear();

}

graphicsitem2.cpp

#include "graphicsitem2.h"

#include <QPainter>
#include <QCursor>
#include <QKeyEvent>
#include <QGraphicsView>
#include <QDebug>

GraphicsItem2::GraphicsItem2()
{
    m_color=Qt::black;
    setFlag(QGraphicsItem::ItemIsFocusable);
    setFlag(QGraphicsItem::ItemIsMovable);
}

QRectF GraphicsItem2::boundingRect()const{
    qreal penWidth=1;
    return QRectF(0,0-penWidth/2,100+penWidth,100+penWidth);
}

void GraphicsItem2::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget){
    Q_UNUSED(option)
    Q_UNUSED(widget)
    if(m_flag==1||m_flag==2){
        painter->setBrush(m_color);
        painter->drawRoundedRect(0,0,100,100,5,5);
    }
    else if(m_flag==3){
        painter->setBrush(m_color);
        painter->drawEllipse(0,0,100,100);
    }
    else{
        painter->setBrush(m_color);
        painter->drawRect(0,0,100,100);
    }
}

void GraphicsItem2::setColor(const QColor &color){
    m_color=color;
}

void GraphicsItem2::setMyFlag(int flag)
{
    m_flag=flag;
}

int GraphicsItem2::getMyFlag()
{
    return m_flag;
}

void GraphicsItem2::reflush()
{
    this->update();
}

void GraphicsItem2::ChangeRang()
{

    prepareGeometryChange();
}


void GraphicsItem2::mousePressEvent(QGraphicsSceneMouseEvent *event){
    Q_UNUSED(event)
    setFocus();
    setCursor(Qt::ClosedHandCursor);
}

main.cpp

#include <QApplication>
#include <QDebug>
#include "graphicsitem.h"
#include "graphicsitem2.h"

#include <QGraphicsScene>
#include <QGraphicsRectItem>
#include <QGraphicsView>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QGraphicsScene scene;
    GraphicsItem *item=new GraphicsItem;
    GraphicsItem2 *item2=new GraphicsItem2;
    scene.addItem(item);
    scene.addItem(item2);
    item->setPos(150,150);
    item2->setMyFlag(1);
    item->setColor(Qt::red);
    item2->setPos(0,0);
    item2->setColor(Qt::blue);

    GraphicsItem2 *item3=new GraphicsItem2;
    scene.addItem(item3);
    item3->setPos(-100,-100);
    item3->setMyFlag(3);
    item3->setColor(Qt::green);

    GraphicsItem2 *item4=new GraphicsItem2;
    scene.addItem(item4);
    item4->setPos(150,400);
    item4->setMyFlag(4);
    item4->setColor(Qt::black);

    scene.setSceneRect(0,0,700,500);
    QGraphicsView view(&scene);
    view.setWindowTitle("CSDN IT1995");

    view.resize(700,500);
    view.show();

    return a.exec();
}