在Qt中按下鼠标滚轮时的平移C++

Question

我有一个应用程序，可以在Qt Creator中使用鼠标滚轮来处理缩放。

CPP

void QNodeView::wheelEvent(QWheelEvent* event) { 

    setTransformationAnchor(QGraphicsView::AnchorUnderMouse); 

    // Scale the view/do the zoom 
    double scaleFactor = 1.15; 
    if(event->delta() > 0) { 
     // Zoom in 
     scale(scaleFactor, scaleFactor); 
    } else { 
     // Zooming out 
     scale(1.0/scaleFactor, 1.0/scaleFactor); 
    } 
} 

这是

protected: 
    //Take over the interaction 
    virtual void wheelEvent(QWheelEvent* event); 

如何添加鼠标中键可进行平移的能力，与被按下的用户拖动头文件 ^h光标？

如果需要的话，我可以发布项目代码。 感谢

项目文件的链接（Qt Creator的项目）

https://www.dropbox.com/s/gbt4qqtdedltxek/QNodesEditor-master_01.zip?dl=0

Answer 1

起初，引入一些新的成员变量到您的浏览器类：

class QNodeView : public QGraphicsView 
{ 
    // ... 

private: 
    int m_originalX = 0; 
    int m_originalY = 0; 
    bool m_moving = false; 
}; 

然后重新实现mousePressEvent()，mouseMoveEvent()和mouseReleaseEvent()。

void QNodeView::mousePressEvent(QMouseEvent* event) 
{ 
    if (event->button() == Qt::MiddleButton) 
    { 
     // store original position 
     m_originalX = event->x(); 
     m_originalY = event->y(); 

     // set the "moving" state 
     m_moving = true; 
    } 
} 

void QNodeView::mouseMoveEvent(QMouseEvent* event) 
{ 
    if (m_moving) 
    { 
     // panning operates in the scene coordinates using x,y 
     QPointF oldp = mapToScene(m_originalX, m_originalY); 
     QPointF newp = mapToScene(event->pos()); 
     QPointF translation = newp - oldp; 

     translate(translation.x(), translation.y()); 

     m_originalX = event->x(); 
     m_originalY = event->y(); 
    } 
} 

void QNodeView::mouseReleaseEvent(QMouseEvent* event) 
{ 
    if (event->button() == Qt::MiddleButton) 
    { 
     m_moving = false; 
    } 
}