c++ - QGraphicsScene::removeItem: item场景和这个场景不一样

Question

QGraphicsScene::removeItem 有一些奇怪的地方，当我从场景中删除两个项目时，我收到以下消息:

QGraphicsScene::removeItem: item 0x5edb28's scene (0x0) is different from this scene (0x5e7790)
QGraphicsScene::removeItem: item 0x5edc18's scene (0x0) is different from this scene (0x5e7790)

即使这两个项目在场景中。

我已经根据场景检查了项目场景，但它返回 true:

if(Player->scene() == m_scene){
    m_scene->addText("Same"); // this text is added
}else{
    m_scene->addText("Different");
}

m_scene 来自这个类:

class Game : public QGraphicsView
{
    Q_OBJECT

    public:
        Game();

    public slots:
        void FixedUpdate();

    signals:


    private:
        QRectF *sceneSize;
        QGraphicsScene *m_scene;
        QGraphicsRectItem *m_rect;
        QTimer *m_timer;
        Character *Player;
        Character *enemy;

};

Character类是继承自QGraphicsPolygonItem的类:

class Character : public QObject, public QGraphicsPolygonItem
{
    Q_OBJECT

    public:
        Character(qreal x, qreal y, qreal w, qreal h, QString tag, QGraphicsScene *scene = 0, QGraphicsItem *parent = 0);
        Character(QRectF rectF, QString tag, QGraphicsScene *scene = 0, QGraphicsItem *parent = 0);
        Character(QString tag, QGraphicsScene *scene = 0, QGraphicsItem *parent = 0);
        void setValue(qreal x, qreal y, qreal w, qreal h);
        void setVelocity(qreal vx, qreal vy);
        void setVelocityX(qreal vx);
        void setVelocityY(qreal vy);
        void setTag(QString tag);
        qreal vx() const;
        qreal vy() const;
        qreal w() const;
        qreal h() const;
        QString tag() const;
        QGraphicsScene *currentScene() const;
        void fixedUpdate();
        void removeCharacter();

    signals:


    public slots:


    private:
        qreal m_x;
        qreal m_y;
        qreal m_w;
        qreal m_h;
        qreal m_vx;
        qreal m_vy;
        QString m_tag;
        QGraphicsScene *m_scene;
};

这就是我调用 removeItem

的地方

void Game::FixedUpdate(){
    if(Player->collidesWithItem(enemy)){
        Player->setVelocityX(0);
        enemy->setVelocityX(0);

        //removeCharacter just call scene()->removeItem(this);
        Player->removeCharacter();
        enemy->removeCharacter();
    }else{
        Player->fixedUpdate();
        enemy->fixedUpdate();

    }
}

有人可以解释一下为什么我会收到这些消息吗？

编辑:

Game::Game(){
    sceneSize = new QRectF(0, 0, 640, 480);
    m_scene = new QGraphicsScene(*sceneSize, this);
    setScene(m_scene);
    Player = new Character(QRectF(0, 0, 50, 50), "player", m_scene);
    Player->setVelocityX(1.5);
    //m_scene->addItem(Player);

    enemy = new Character(QRectF(500, 0, 20, 20), "enemy", m_scene);
    enemy->setVelocityX(-0.5);
    //m_scene->addItem(enemy);

    //m_scene->addText(QString::number(Player->x() + Player->vx()));

    if(Player->scene() == m_scene){
        m_scene->addText("Same");
    }else{
        m_scene->addText("Different");
    }

    m_timer = new QTimer(this);
    connect(m_timer, SIGNAL(timeout()), this, SLOT(FixedUpdate()));
    m_timer->start(1000 / 60);
}

Answer 1

终于找到了。

它在 Game::FixedUpdate() 函数中，它是 Player->collidesWithItem(enemy) 是 true 即使在指针被删除之后从现场移除。所以我在检查碰撞之前进行了检查，如下所示:

void Game::FixedUpdate(){
    if(Player->scene() != NULL && enemy->scene() != NULL){
        if(Player->collidesWithItem(enemy)){
            Player->setVelocityX(0);
            enemy->setVelocityX(0);

            //removeCharacter just call scene()->removeItem(this);
            Player->removeCharacter();
            enemy->removeCharacter();
        }else{
            Player->fixedUpdate();
            enemy->fixedUpdate();

        }
    }
}

删除后不显示消息。