qt图表按住鼠标中键移动视图

Question

我目前正在使用Qts Chart绘图工具。我现在有一个情节，我可以通过使用由this示例（小调整）提供的chartview类来放大和缩小。 我希望看到不仅可以缩放的能力，还可以将我的视图按下鼠标中键（这在其他应用程序中使用很多，因此非常直观）。

我该如何在Qt中做到这一点？如何检查鼠标中键是否被按下并释放，如果鼠标在按下鼠标中键时移动，则更改我的视图...

我确定有人编写过此代码，一个小例子/帮助。

Answer 1

你需要从QChartView派生类和重载鼠标事件：

class ChartView: public QChartView 
{ 
    Q_OBJECT 

public: 
    ChartView(Chart* chart, QWidget *parent = 0); 

protected: 

    virtual void mousePressEvent(QMouseEvent *event) override; 
    virtual void mouseMoveEvent(QMouseEvent *event) override; 

private: 

    QPointF m_lastMousePos; 
}; 

ChartView::ChartView(Chart* chart, QWidget *parent) 
    : QChartView(chart, parent) 
{ 
    setDragMode(QGraphicsView::NoDrag); 
    this->setMouseTracking(true); 
} 

void ChartView::mousePressEvent(QMouseEvent *event) 
{ 
    if (event->button() == Qt::MiddleButton) 
    { 
     QApplication::setOverrideCursor(QCursor(Qt::SizeAllCursor)); 
     m_lastMousePos = event->pos(); 
     event->accept(); 
    } 

    QChartView::mousePressEvent(event); 
} 

void ChartView::mouseMoveEvent(QMouseEvent *event) 
{ 
    // pan the chart with a middle mouse drag 
    if (event->buttons() & Qt::MiddleButton) 
    { 
     QRectF bounds = QRectF(0,0,0,0); 
     for(auto series : this->chart()->series()) 
      bounds.united(series->bounds()) 

     auto dPos = this->chart()->mapToValue(event->pos()) - this->chart()->mapToValue(m_lastMousePos); 

     if (this->rubberBand() == QChartView::RectangleRubberBand) 
      this->chart()->zoom(bounds.translated(-dPos.x(), -dPos.y())); 
     else if (this->rubberBand() == QChartView::HorizontalRubberBand) 
      this->chart()->zoom(bounds.translated(-dPos.x(), 0)); 
     else if (this->rubberBand() == QChartView::VerticalRubberBand) 
      this->chart()->zoom(bounds.translated(0, -dPos.y())); 

     m_lastMousePos = event->pos(); 
     event->accept(); 
    } 

    QChartView::mouseMoveEvent(event); 
}