【Qt】Qt再學習（二）：Chart Themes Example（常用圖表）

1、簡介

該示例中展示了各種圖表以及在不同內建主題下的外觀。

2、使用到的類

QChart：圖表抽象類，繼承自QGraphicsWidget
QChartView：顯示圖表視窗，繼承自QGraphicsView
QLineSeries：折線圖
QAreaSeries：面積圖
QStackedBarSeries：分段條狀圖
QScatterSeries：散點圖
QSplineSeries：曲線圖
QPieSeries：餅圖

3、各種圖表建立demo

QChart *ThemeWidget::createAreaChart() const
{
    QChart *chart = new QChart();
    chart->setTitle("Area chart");

    // The lower series initialized to zero values
    QLineSeries *lowerSeries = 0;
    QString name("Series ");
    int nameIndex = 0;
    for (int i(0); i < m_dataTable.count(); i++) {
        QLineSeries *upperSeries = new QLineSeries(chart);
        for (int j(0); j < m_dataTable[i].count(); j++) {
            Data data = m_dataTable[i].at(j);
            if (lowerSeries) {
                const QVector<QPointF>& points = lowerSeries->pointsVector();
                upperSeries->append(QPointF(j, points[i].y() + data.first.y()));
            } else {
                upperSeries->append(QPointF(j, data.first.y()));
            }
        }
        QAreaSeries *area = new QAreaSeries(upperSeries, lowerSeries);
        area->setName(name + QString::number(nameIndex));
        nameIndex++;
        chart->addSeries(area);
        lowerSeries = upperSeries;
    }

    chart->createDefaultAxes();
    chart->axes(Qt::Horizontal).first()->setRange(0, m_valueCount - 1);
    chart->axes(Qt::Vertical).first()->setRange(0, m_valueMax);
    // Add space to label to add space between labels and axis
    QValueAxis *axisY = qobject_cast<QValueAxis*>(chart->axes(Qt::Vertical).first());
    Q_ASSERT(axisY);
    axisY->setLabelFormat("%.1f  ");

    return chart;
}

QChart *ThemeWidget::createBarChart(int valueCount) const
{
    Q_UNUSED(valueCount);
    QChart *chart = new QChart();
    chart->setTitle("Bar chart");

    QStackedBarSeries *series = new QStackedBarSeries(chart);
    for (int i(0); i < m_dataTable.count(); i++) {
        QBarSet *set = new QBarSet("Bar set " + QString::number(i));
        for (const Data &data : m_dataTable[i])
            *set << data.first.y();
        series->append(set);
    }
    chart->addSeries(series);

    chart->createDefaultAxes();
    chart->axes(Qt::Vertical).first()->setRange(0, m_valueMax * 2);
    // Add space to label to add space between labels and axis
    QValueAxis *axisY = qobject_cast<QValueAxis*>(chart->axes(Qt::Vertical).first());
    Q_ASSERT(axisY);
    axisY->setLabelFormat("%.1f  ");

    return chart;
}

QChart *ThemeWidget::createLineChart() const
{
    QChart *chart = new QChart();
    chart->setTitle("Line chart");
    QString name("Series ");
    int nameIndex = 0;
    for (const DataList &list : m_dataTable) {
        QLineSeries *series = new QLineSeries(chart);
        for (const Data &data : list)
            series->append(data.first);
        series->setName(name + QString::number(nameIndex));
        nameIndex++;
        chart->addSeries(series);
    }
    chart->createDefaultAxes();
    chart->axes(Qt::Horizontal).first()->setRange(0, m_valueMax);
    chart->axes(Qt::Vertical).first()->setRange(0, m_valueCount);

    // Add space to label to add space between labels and axis
    QValueAxis *axisY = qobject_cast<QValueAxis*>(chart->axes(Qt::Vertical).first());
    Q_ASSERT(axisY);
    axisY->setLabelFormat("%.1f  ");
    return chart;
}

QChart *ThemeWidget::createPieChart() const
{
    QChart *chart = new QChart();
    chart->setTitle("Pie chart");

    QPieSeries *series = new QPieSeries(chart);
    for (const Data &data : m_dataTable[0]) {
        QPieSlice *slice = series->append(data.second, data.first.y());
        if (data == m_dataTable[0].first()) {
            // Show the first slice exploded with label
            slice->setLabelVisible();
            slice->setExploded();
            slice->setExplodeDistanceFactor(0.5);
        }
    }
    series->setPieSize(0.4);
    chart->addSeries(series);

    return chart;
}

QChart *ThemeWidget::createSplineChart() const
{
    QChart *chart = new QChart();
    chart->setTitle("Spline chart");
    QString name("Series ");
    int nameIndex = 0;
    for (const DataList &list : m_dataTable) {
        QSplineSeries *series = new QSplineSeries(chart);
        for (const Data &data : list)
            series->append(data.first);
        series->setName(name + QString::number(nameIndex));
        nameIndex++;
        chart->addSeries(series);
    }

    chart->createDefaultAxes();
    chart->axes(Qt::Horizontal).first()->setRange(0, m_valueMax);
    chart->axes(Qt::Vertical).first()->setRange(0, m_valueCount);

    // Add space to label to add space between labels and axis
    QValueAxis *axisY = qobject_cast<QValueAxis*>(chart->axes(Qt::Vertical).first());
    Q_ASSERT(axisY);
    axisY->setLabelFormat("%.1f  ");
    return chart;
}

QChart *ThemeWidget::createScatterChart() const
{
    // scatter chart
    QChart *chart = new QChart();
    chart->setTitle("Scatter chart");
    QString name("Series ");
    int nameIndex = 0;
    for (const DataList &list : m_dataTable) {
        QScatterSeries *series = new QScatterSeries(chart);
        for (const Data &data : list)
            series->append(data.first);
        series->setName(name + QString::number(nameIndex));
        nameIndex++;
        chart->addSeries(series);
    }

    chart->createDefaultAxes();
    chart->axes(Qt::Horizontal).first()->setRange(0, m_valueMax);
    chart->axes(Qt::Vertical).first()->setRange(0, m_valueCount);
    // Add space to label to add space between labels and axis
    QValueAxis *axisY = qobject_cast<QValueAxis*>(chart->axes(Qt::Vertical).first());
    Q_ASSERT(axisY);
    axisY->setLabelFormat("%.1f  ");
    return chart;
}