我的工作环境:Qt 5.8 MSVC2015 64bit, QT GraphicsView, QGraphicsRectItem, Windows 7 64 bit。
问题:当我放大和缩小 GraphicsView 时,我调用 GraphicsView 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。
我的班级层次结构:
class GraphicsView : public QGraphicsView
class mySquare : public QObject, public QGraphicsRectItem
class Scene : public QGraphicsScene
代码 :
//////*****在QGraphicsRectItem中绘制矩形*****///////////
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();
}
这是git代码
我花了几天和几个小时,但仍然无法找出为什么 QGraphicsRectItem 在调用 scale 方法时无法打印。任何建议都受到高度赞赏?