Qt学习笔记-使用shape() 使得碰撞更加精确

官方解析如下：

这英语就我就不翻译了，就他说的，很好理解，

我就直接来个例子好了。

运行截图如下：

代码如下：

myitem.h

#ifndef MYITEM_H
#define MYITEM_H

#include <QGraphicsItem>

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

    void setMyFlag(bool flag);
    bool getMyFlag();
    void changeMyFlag();

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

private:
    QColor m_color;
    bool m_flag;
};

#endif // MYITEM_H

myitem.cpp

#include "myitem.h"
#include <QPainter>
#include <QCursor>
#include <QKeyEvent>
#include <QGraphicsView>
#include <QDebug>
#include <QPainterPath>

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

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

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

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

QPainterPath MyItem::shape() const
{
    QPainterPath path;
    path.addEllipse(boundingRect());
    return path;
}

void MyItem::setMyFlag(bool flag){
    m_flag=flag;
}

bool MyItem::getMyFlag()
{
    return m_flag;
}

void MyItem::changeMyFlag(){
    m_flag=!m_flag;
}

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

void MyItem::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{
        moveBy(10,0);
    }

    QList<QGraphicsItem*>list=collidingItems();
    if(!list.isEmpty()){
        if(((MyItem*)(list.at(0)))->getMyFlag()==true){
            ((MyItem*)(list.at(0)))->setColor(Qt::blue);
            ((MyItem*)(list.at(0)))->changeMyFlag();
            ((MyItem*)(list.at(0)))->update();
        }
        else{
            ((MyItem*)(list.at(0)))->setColor(Qt::red);
            ((MyItem*)(list.at(0)))->changeMyFlag();
            ((MyItem*)(list.at(0)))->update();
        }
    }
}

main.cpp

#include <QApplication>
#include <QGraphicsScene>
#include <QGraphicsRectItem>
#include <QGraphicsView>
#include "myitem.h"

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

    QGraphicsScene scene;
    MyItem *item=new MyItem;
    MyItem *item2=new MyItem;
    scene.addItem(item);
    scene.addItem(item2);
    item->setPos(100,100);
    item2->setPos(300,300);
    item->setColor(Qt::red);
    item2->setColor(Qt::blue);
    scene.setSceneRect(0,0,700,500);

    QGraphicsView view(&scene);
    view.resize(700,500);
    view.show();
    view.centerOn(item);

    return a.exec();
}