Question

我正在c ++端填充QLineSeries数据，并且QML图表应该消耗它们（并随着它们的变化而更新）。数据生产者已连接到newData，后者已添加到系列数据中，并且应该触发重新绘制图表。

以前，LineSeries是在QML中操作的，但现在我不知道如何使c ++ QLineSeries实例可供QML访问。

// ...
#include<QtCharts/QLineSeries>
using namespace QtCharts;

/* class holding all data to be displayed as properties */
class UiData: public QObject{
   Q_OBJECT
   Q_PROPERTY(QLineSeries *xy READ getXy NOTIFY xyChanged);
   QLineSeries* getXy(){return &xy; }
   signals:
      void xyChanged();
   public slots:
      void newData(float x, float y){
         xy.append(x,y);
         emit xyChanged();
      }
   private:
      QLineSeries xy;
}

int main(int argc, char* argv[]){
   QApplication app(argc,argv);
   QQmlApplicationEngine engine;
   UiData uiData;
   /* make the instance accessiblt from QML */
   engine.rootContext()->setContextProperty("uiData",&uiData);
   engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
   // ...
   return qApp->exec();
}

main.qml：

ChartView{
   ValueAxis{
      id: _axisX;
   }
   ValueAxis{
      id: _axisY;
   }
   /*
   BEFORE:
   data in QML: easy, plus had JS slot calling _xySeries.append(...)
   */
   LineSeries{
      id: _xySeries;
      axisX: _axisX;
      axisY: _axisY;
   }

   /*
   NOW:
   how to use an already existing LineSeries instance (uiData.xy),
   and only change a few attributes, like axisX and axisY?

   Something like this:

   LineSeries(uiData.xy) {
      axisX: _axisX;
      axisY: _axisY;
   }

   or like this:

   component.onCompleted:{
      // where is something like ChartView.addSeries?
      // (there is ChartView.removeSeries already)
      uiData.xy.axisX=_axisX;                    
      uiData.xy.axisY=_axisY;
      addSeries(uiData.xy);
   }
   */
};

对此有一个好的解决方案吗？

在极端情况下，我还可以在c ++中创建整个ChartView（但再次如何将其插入到QML中呢？）。

Answer 1

可以说LineSeries是QLineSeries +其他功能，因此ChartView使用这些其他功能。

您必须执行的操作是访问LineSeries中的UiData，为此您必须使用存储位置。

class UiData: public QObject{
    Q_OBJECT
    Q_PROPERTY(QLineSeries* xy READ xy WRITE setXy NOTIFY xyChanged)
public:
    ...
    QLineSeries *xy() const
    {
        return mXy;
    }
    void setXy(QLineSeries *xy)
    {
        if(mXy == xy) return;
        if(mXy)
            if(mXy->parent() == this) // is owner
                delete mXy;
        mXy = xy;
        emit xyChanged();
    }
public slots:
    void newData(qreal x, qreal y){
        if(mXy){
            mXy->append(x, y);
        }
    }
    ...
signals:
    void xyChanged();
    ...
private:
    QLineSeries *mXy;
};

*。qml

ChartView{
    ValueAxis{
        id: _axisX;
    }
    ValueAxis{
        id: _axisY;
    }
    LineSeries{
        id: _xySeries;
        axisX: _axisX;
        axisY: _axisY;
    }
}
Component.onCompleted: uiData.xy = _xySeries // <----

如您所见，QLineSeries不是在C ++中创建的，但是指针仅用于引用LineSeries。

完整的示例可以在下面的link中找到。

如何使用从C ++公开的系列数据在QML中创建图表

1 个答案: