QGraphicsView Scale＆QGraphicsRectItem paint未能调用

我的工作环境：Qt 5.8 MSVC2015 64位，QT GraphicsView，QGraphicsRectItem，Windows 7 64位。QGraphicsView Scale＆QGraphicsRectItem paint未能调用

发布时间：当我放大&缩小GraphicsView时，我调用GraphicsView的缩放方法。但是当我将QGraphicsRectItem添加到场景时，它未能调用其绘制方法。

我的类层次：

class GraphicsView : public QGraphicsView 
    class mySquare : public QObject, public QGraphicsRectItem 
    class Scene : public QGraphicsScene

代码：

////// *****在QGraphicsRectItem绘制矩形***** /////// /////

void mySquare::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) 
{ 
     QRectF rect(0,0,_width,_height); 
     painter->drawRect(rect); 
} 

    void GraphicsView::wheelEvent(QWheelEvent * event) 
{ 
    int angle = event->angleDelta().y(); // angle will tell you zoom in or out. 
    double scaleFactor = 1.15; //How fast we zoom 
    setTransformationAnchor(QGraphicsView::AnchorUnderMouse); 
    if (angle > 0) 
    { 
     qDebug()<<"Zoom in"; 
     scale(scaleFactor, scaleFactor); 
    } 
    else 
    { 
     qDebug()<<"Zoom out"; 
     scale(1.0/scaleFactor, 1.0/scaleFactor); 
    } 
     mySquare _square = new mySquare(0,blankImage); 
     _square->setPos(QPointF(0, 0)); 
     //add square to scene. 
//Bug!!! Why after scale function call, _square failed to draw rect in paint method. 
     _scene->addItem(_square); 
     _square->update(); 
}

这里是混帐code

我花天&小时，但仍然无法找到为什么QGraphicsRectItem无法打印，当调用缩放方法。任何建议是高度赞赏？

来源

2017-06-20 Sandy

线 “mySquare _square =新mySquare（0，blankImage）;”不会编译。请编辑您的问题以显示真实的代码。 –

更新的git代码url： https://github.com/SandyWare/ImageRender – Sandy

注意从'QObject'和'QGraphicsRectItem'扩展有一个用于这个特殊目的的类[QGraphicsObject]（http：//doc.qt .io/qt-5.9/qgraphicsobject.html） – Elia

感谢您的帮助。我通过重写QGraphicsView缩放方法来找到解决方案。变化：类mySquare：公共QGraphicsObject

void GraphicsView::scale(qreal scaleFactor) 
{ 
    QRectF r(0, 0, 1, 1); // A reference 
    qreal factor = transform().scale(scaleFactor, scaleFactor).mapRect(r).width(); // absolute zoom factor 
    ((rFactor > 0 ) 
    { 
      qDebug()<<"Zoom in"; 
    } 
    else 
    { 
      qDebug()<<"Zoom out"; 
     } 

     mySquare _square = new mySquare(0,blankImage); 
     _square->setPos(QPointF(0, 0)); 
     _scene->addItem(_square); 
     _square->update(); 
    } 
    QGraphicsView::scale(scaleFactor, scaleFactor); 
}

来源

2017-06-21 14:23:15 Sandy

QGraphicsView Scale＆QGraphicsRectItem paint未能调用

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