如何使用从 C++ 公开的系列数据在 QML 中创建图表
How to create chart in QML with series data exposed from c++
我正在 c++ 端填充 QLineSeries
数据,QML 图表应该使用它们(并随着它们的变化而更新)。数据生成器连接到添加到系列数据的 newData
,这应该会触发图表的重绘。
以前,LineSeries
是在 QML 中操作的,但现在我不知道如何使 QML 可以访问 c++ QLineSeries
实例。
// ...
#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);
}
*/
};
有什么好的解决办法吗?
在极端情况下,我还可以用 c++ 创建整个 ChartView(但话又说回来,如何将它插入到 QML 中?)。
可以说 LineSeries
是 QLineSeries
+ 其他功能,所以 ChartView
使用那些其他功能。
你必须做的是访问UiData
中的LineSeries
,为此你必须使用内存位置。
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,C++中并未创建QLineSeries
,指针仅用于引用LineSeries
。
完整的例子可以在下面link.
中找到
我正在 c++ 端填充 QLineSeries
数据,QML 图表应该使用它们(并随着它们的变化而更新)。数据生成器连接到添加到系列数据的 newData
,这应该会触发图表的重绘。
以前,LineSeries
是在 QML 中操作的,但现在我不知道如何使 QML 可以访问 c++ QLineSeries
实例。
// ...
#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);
}
*/
};
有什么好的解决办法吗?
在极端情况下,我还可以用 c++ 创建整个 ChartView(但话又说回来,如何将它插入到 QML 中?)。
可以说 LineSeries
是 QLineSeries
+ 其他功能,所以 ChartView
使用那些其他功能。
你必须做的是访问UiData
中的LineSeries
,为此你必须使用内存位置。
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,C++中并未创建QLineSeries
,指针仅用于引用LineSeries
。
完整的例子可以在下面link.
中找到