[英]QML QTQuick ChartView pass pointer to C++
I'm trying to make an Oscilloscope like Qt Quick application, based on the qtcharts-qmloscilloscope-example here我正在尝试基于 qtcharts-qmloscilloscope-example here制作一个类似 Qt Quick 应用程序的示波器
In this example the traces (a QTQuick ChartView) are pre-allocated in the QML and updated via a timer.在此示例中,跟踪(QTQuick ChartView)在 QML 中预先分配并通过计时器进行更新。
I would like to be able to add and remove traces at runtime.我希望能够在运行时添加和删除跟踪。
The existing application passes a reference to the underlying data array as QAbstractSeries of QPointF objects.现有应用程序将底层数据数组的引用作为 QPointF 对象的 QAbstractSeries 传递。 This action is triggered on a Timer, thus:
此操作是在计时器上触发的,因此:
Timer {
id: refreshTimer
interval: 1 / 1 * 1000 // 1 Hz
running: dataSource.isRunning
repeat: true
onTriggered: {
dataSource.updateTime();
//dataSource.update(chartView.series(0));
//dataSource.update(chartView.series(1));
//dataSource.update(chartView.series(2));
dataSource.update(chartView);
}
}
And the existing update method looks like this:现有的更新方法如下所示:
void DataSource::update(QAbstractSeries * series)
{
...
}
This is OK if you only want a fixed number of traces and they are all updated individually.如果您只需要固定数量的跟踪并且它们都单独更新,那么这没问题。 But I would like to be able to add traces as they are turned on and off.
但我希望能够在打开和关闭时添加跟踪。
I've tried to pass the chartView ID to an update(QChartView *) function but this always breaks with a null pointer.我试图将 chartView ID 传递给 update(QChartView *) 函数,但这总是以空指针中断。
Q_INVOKABLE void DataSource::update(QChartView * view)
{
...
}
I've also tried using window->findChildren at the top level and passing that to the instance of DataSource.我还尝试在顶层使用 window->findChildren 并将其传递给 DataSource 的实例。 That gets a valid pointer but of type QQuickItem.
这会得到一个有效的指针,但类型为 QQuickItem。 If I cast that to a QChartView I also get a null pointer.
如果我将它转换为 QChartView,我也会得到一个空指针。
How to I correctly pass a pointer to a QChartView object to C++?如何正确地将指向 QChartView 对象的指针传递给 C++?
ChartView is not a QChartView but a QQuickItem so casting does not work. ChartView 不是 QChartView 而是 QQuickItem,因此转换不起作用。
So you can not access the methods directly but use the QMetaObject as shown below:所以你不能直接访问这些方法,而是使用 QMetaObject ,如下所示:
helper.h helper.h
#ifndef HELPER_H
#define HELPER_H
#include <QObject>
class QQuickItem;
class Helper : public QObject
{
Q_OBJECT
public:
using QObject::QObject;
Q_INVOKABLE void createSerie(QQuickItem *chartview);
Q_INVOKABLE void removeAllSeries(QQuickItem *chartview);
};
#endif // HELPER_H
helper.cpp helper.cpp
#include "helper.h"
#include <QAbstractAxis>
#include <QAbstractSeries>
#include <QLineSeries>
#include <QMetaObject>
#include <QQuickItem>
#include <random>
#include <cstring>
QT_CHARTS_USE_NAMESPACE
void Helper::createSerie(QQuickItem *chartview){
if(!chartview)
return;
const QMetaObject *mo = chartview->metaObject();
if(std::strcmp(mo->className(), "QtCharts::DeclarativeChart") != 0)
return;
int ix = mo->indexOfEnumerator("SeriesType");
QMetaEnum me = mo->enumerator(ix);
int type = me.keyToValue("SeriesTypeLine");
QAbstractAxis *axis_x = nullptr;
QMetaObject::invokeMethod(chartview, "axisX", Qt::DirectConnection,
Q_RETURN_ARG(QAbstractAxis *, axis_x));
QAbstractAxis *axis_y = nullptr;
QMetaObject::invokeMethod(chartview, "axisY", Qt::DirectConnection,
Q_RETURN_ARG(QAbstractAxis *, axis_y));
QAbstractSeries *serie = nullptr;
QMetaObject::invokeMethod(chartview, "createSeries", Qt::DirectConnection,
Q_RETURN_ARG(QAbstractSeries *, serie),
Q_ARG(int, type),
Q_ARG(QString, "serie from c++"),
Q_ARG(QAbstractAxis *, axis_x),
Q_ARG(QAbstractAxis *, axis_y));
if(QLineSeries *line_serie = qobject_cast<QLineSeries *>(serie)){
static std::default_random_engine e;
static std::uniform_real_distribution<> dis(0, 3);
for(int i=0; i < 14; i++){
line_serie->append(i, dis(e));
}
}
}
void Helper::removeAllSeries(QQuickItem *chartview){
if(!chartview)
return;
const QMetaObject *mo = chartview->metaObject();
if(std::strcmp(mo->className(), "QtCharts::DeclarativeChart") != 0)
return;
QMetaObject::invokeMethod(chartview, "removeAllSeries", Qt::DirectConnection);
}
main.qml主文件
import QtQuick 2.14
import QtQuick.Window 2.14
import QtQuick.Layouts 1.14
import QtQuick.Controls 2.4
import QtCharts 2.14
Window {
visible: true
width: 640
height: 480
title: qsTr("Hello World")
ColumnLayout{
anchors.fill: parent
RowLayout{
Button{
text: "Create serie"
Layout.fillWidth: true
onClicked: helper.createSerie(chartview)
}
Button{
text: "Clear series"
Layout.fillWidth: true
onClicked: helper.removeAllSeries(chartview);
}
}
ChartView {
id: chartview
title: "Line"
antialiasing: true
Layout.fillWidth: true
Layout.fillHeight: true
LineSeries {
name: "LineSeries"
XYPoint { x: 0; y: 0 }
XYPoint { x: 3; y: 2.1 }
XYPoint { x: 8; y: 3.3 }
XYPoint { x: 10; y: 2.1 }
XYPoint { x: 11; y: 4.9 }
XYPoint { x: 12; y: 3.0 }
XYPoint { x: 13; y: 3.3 }
}
axes: [
ValueAxis{
id: xAxis
min: 1.0
max: 15.0
},
ValueAxis{
id: yAxis
min: 0.0
max: 5.0
}
]
}
}
}
Better variant exists without using QMetaObject::invokeMethod()
: it is possible to use QChart
directly.不使用
QMetaObject::invokeMethod()
存在更好的变体:可以直接使用QChart
。 Just need to extend following solution "Push QML ChartView updates from c++" a bit:只需要稍微扩展以下解决方案“从 C++ 推送 QML ChartView 更新” :
* .h * .h
public:
Q_INVOKABLE void setSeries(QAbstractSeries *series);
[...]
private:
QXYSeries *mSeries;
QChart *mChart;
[...]
* .cpp * .cpp
void DataSource::setSeries(QAbstractSeries *series)
{
if (series) {
mSeries = static_cast<QXYSeries *>(series);
mChart = mSeries->chart();
}
}
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