将数据添加到 QLineSeries 后如何更新/重绘 QChart? [英] How to update/redraw QChart after data is added to QLineSeries?

问题描述

我正在生成一些我想使用 QChart 绘制图表的数据 &朋友们.这是我第一次使用 QChart，所以基本上我所做的是复制 QLineSeries Example 并根据我的需要修改它.我当前的代码如下所示:

I am generating some data that I want to chart using QChart & friends. This is my first time using QChart, and so basically what I did was copy the QLineSeries Example and modify it to my needs. My current code looks like this:

    quint64 last=0;
    quint64 *lastp=&last;

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
    , series( nullptr )
{
    ui->setupUi(this);
    QChart *chart = new QChart();
    series=new QLineSeries(chart);
    chart->legend()->hide();
    chart->addSeries(series);
    chart->createDefaultAxes();
    chart->setTitle("Simple line chart example");
    QChartView *chartView = new QChartView(chart);
    chartView->setRenderHint(QPainter::Antialiasing);
    setCentralWidget(chartView);
    GeneticTask *gTask = new GeneticTask();
    connect(gTask, &GeneticTask::point, this, [=](QPointF pt) {
        // New point added to series
        *series<<pt;
        // Limit updates to once per second
        quint64 now=QDateTime::currentMSecsSinceEpoch();
        if(now-(*lastp)>1000) {
            qDebug()<<"UPDATE";
            // [A] WHAT TO PUT HERE TO HAVE CHART REDRAW WITH NEW DATA?
            *lastp=now;
        }
    }
    );
    QThreadPool::globalInstance()->start(gTask);
}

当我运行此代码时，我希望我的新数据显示在图表中，但事实并非如此，所以我的问题是:如何更新图表以显示新数据? 换句话说，我应该在注释内容为 [A] 的代码中放什么?

When I run this code I would expect my new data to show up in the graph, but it does not, so my question is: How can I have the chart update to show the new data? In other words, what should I put in the code where the comment reads [A]?

推荐答案

使用运算符 << 或 append<将值附加到 QLineSeries/code> 方法应该重新绘制图形.如果由于某种原因没有发生，您可以尝试调用 QChartView 上的 repaint 方法.

Appending a value to QLineSeries using the operator << or the append method should repaint the graph. If it does not happen form some reason, you could trying calling the repaint method on the QChartView.

以下是一些代码，在添加数据后将数据居中，上限为每秒一次:

Here is some code that will center the data once it is added with a cap of at most once per second:

// Global or class scope or
qreal max=-10000000000;
qreal min=-max;
qreal *maxp=&max;
qreal *minp=&min;

// Same scope as before
connect(gTask, &GeneticTask::point, this, [=](QPointF pt) {
        if(pt.y()>*maxp) {
            *maxp=pt.y();
        }
        if(pt.y()<*minp) {
            *minp=pt.y();
        }
        *series<<pt;
        quint64 now=QDateTime::currentMSecsSinceEpoch();
        if(now-(*lastp)>1000) {
            qDebug()<<"UPDATE";
            chart->axisX()->setRange(0,series->count());
            chart->axisY()->setRange(*minp,*maxp);

            *lastp=now;
        }
    }
);

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