1.概述

QwtPlotMultiBarChart 是 Qwt 绘图库中的一个类，用于绘制多列柱状图。它可以显示多个柱状条并将它们按照不同的类别分组显示。每个类别下的柱状条可以有不同的颜色和宽度。

以下是类继承关系图：

2.常用方法

设置数据：

• void setSamples (const QVector< QwtSetSample > &)
• void setSamples (const QVector< QVector< double > > &)
• void setSamples (QwtSeriesData< QwtSetSample > *)

设置风格：

• void setStyle (ChartStyle style)

设置间距：

• void setSpacing (int) 设置间距
• void setMargin (int)  设置外边距

设置bar title

• void setBarTitles (const QList< QwtText > &)

设置图例：

• setLegendMode( QwtPlotBarChart::LegendBarTitles );设置图例显示模式
• setLegendIconSize( QSize( 10, 14 ) ); 设置图例图标大小

设置符号：

• void setSymbol (int valueIndex, QwtColumnSymbol *)

3.示例

统计各个年代，各个学校的人数。

#ifndef MULTIBARCHARTWIDGET_H
#define MULTIBARCHARTWIDGET_H

#include <QWidget>

namespace Ui {
class MultiBarChartWidget;
}

class MultiBarChartWidget : public QWidget
{
    Q_OBJECT

public:
    explicit MultiBarChartWidget(QWidget *parent = 0);
    ~MultiBarChartWidget();

private:
    Ui::MultiBarChartWidget *ui;
};

#endif // MULTIBARCHARTWIDGET_H


#include "MultiBarChartWidget.h"
#include "ui_MultiBarChartWidget.h"
#include "qwt_plot.h"
#include "qwt_plot_curve.h"
#include "qwt_text.h"
#include "qwt_legend.h"
#include "qwt_symbol.h"
#include "qwt_plot_marker.h"
#include "qwt_plot_grid.h"
#include "qwt_scale_div.h"
#include "qwt_plot_canvas.h"
#include "qwt_plot_legenditem.h"
#include "qwt_math.h"
#include "qwt_plot_layout.h"
#include "qwt_plot_barchart.h"
#include "qwt_scale_draw.h"
#include "qwt_column_symbol.h"
#include "qwt_plot_renderer.h"
#include "qwt_plot_multi_barchart.h"


//自定义坐标轴
class ScaleDraw : public QwtScaleDraw
{
  public:
    ScaleDraw( Qt::Orientation orientation, const QStringList& labels )
        : m_labels( labels )
    {
        //设置tick长度
        setTickLength( QwtScaleDiv::MinorTick, 0 );
        setTickLength( QwtScaleDiv::MediumTick, 0 );
        setTickLength( QwtScaleDiv::MajorTick, 2 );

        enableComponent( QwtScaleDraw::Backbone, false );

        //设置方向
        if ( orientation == Qt::Vertical )
        {
            setLabelRotation( -60.0 );
        }
        else
        {
            setLabelRotation( -20.0 );
        }

        //设置label对齐方式
        setLabelAlignment( Qt::AlignLeft | Qt::AlignVCenter );
    }

    //重写label方法
    virtual QwtText label( double value ) const QWT_OVERRIDE
    {
        QwtText lbl;

        const int index = qRound( value );
        if ( index >= 0 && index < m_labels.size() )
        {
            lbl = m_labels[ index ];
        }

        return lbl;
    }

  private:
    const QStringList m_labels;
};

static QwtPlot *g_plot = nullptr;
static QwtPlotMultiBarChart *g_multiBarChart = nullptr;

MultiBarChartWidget::MultiBarChartWidget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::MultiBarChartWidget)
{
    ui->setupUi(this);

    g_plot = new QwtPlot(QwtText("XX学校学生"),this);
    ui->verticalLayout->addWidget(g_plot);

    //设置画布
    QwtPlotCanvas* canvas = new QwtPlotCanvas();
    canvas->setLineWidth( 2 );
    canvas->setFrameStyle( QFrame::Box | QFrame::Sunken );
    canvas->setBorderRadius( 10 );

    //设置画布的背景色
    QPalette canvasPalette( QColor( "Plum" ) );
    canvasPalette.setColor( QPalette::WindowText, QColor( "Indigo" ) );
    canvas->setPalette( canvasPalette );

    g_plot->setCanvas( canvas );

    //设置坐标轴标题
    g_plot->setAxisTitle( QwtAxis::YLeft, "人数" );
    g_plot->setAxisTitle( QwtAxis::XBottom, "学校" );

    g_multiBarChart = new QwtPlotMultiBarChart( "Bar Chart " );
    g_multiBarChart->setLayoutPolicy( QwtPlotMultiBarChart::AutoAdjustSamples );
    g_multiBarChart->setSpacing( 10 );
    g_multiBarChart->setMargin( 3 );

    //bar的颜色
    static const char* colors[] = { "DarkOrchid", "SteelBlue", "Gold" };

    const int numSamples = 5;
    const int numBars = sizeof( colors ) / sizeof( colors[0] );

    QList< QwtText > titles;
    for ( int i = 0; i < numBars; i++ )
    {
        QString title("202%1");
        titles += title.arg( i );
    }

    //设置titles
    g_multiBarChart->setBarTitles( titles );
    //设置图标大小
    g_multiBarChart->setLegendIconSize( QSize( 10, 14 ) );

    for ( int i = 0; i < numBars; i++ )
    {
        QwtColumnSymbol* symbol = new QwtColumnSymbol( QwtColumnSymbol::Box );
        symbol->setLineWidth( 2 );
        symbol->setFrameStyle( QwtColumnSymbol::Raised );
        symbol->setPalette( QPalette( colors[i] ) );

        g_multiBarChart->setSymbol( i, symbol );
    }

    //设置数据
    QVector< QVector< double > > series;
    for ( int i = 0; i < numSamples; i++ )
    {
        QVector< double > values;
        for ( int j = 0; j < numBars; j++ )
            values += ( 2 + qwtRand() % 2000 );

        series += values;
    }

    //设置数据
    g_multiBarChart->setSamples( series );

    g_multiBarChart->attach( g_plot );

    //插入图例
    g_plot->insertLegend( new QwtLegend() );

    //设置x范围
    g_plot->setAxisScale( QwtAxis::XBottom, 0, g_multiBarChart->dataSize() - 1, 1.0 );

    //设置y轴自动缩放
    g_plot->setAxisAutoScale( QwtAxis::YLeft );

    QStringList distros;
    distros<<"成都一中"<<"成都二中"<<"成都三中"<<"成都四中"<<"成都五中";
    g_plot->setAxisScaleDraw( QwtAxis::XBottom, new ScaleDraw( Qt::Vertical, distros ) );
    QwtScaleDraw* scaleDraw1 = g_plot->axisScaleDraw( QwtAxis::XBottom );
    scaleDraw1->enableComponent( QwtScaleDraw::Backbone, false );//设置 不显示水平线
    scaleDraw1->enableComponent( QwtScaleDraw::Ticks, false );//设置不显示刻度线

    QwtScaleDraw* scaleDraw2 = g_plot->axisScaleDraw( QwtAxis::YLeft );
    scaleDraw2->enableComponent( QwtScaleDraw::Backbone, true );
    scaleDraw2->enableComponent( QwtScaleDraw::Ticks, true );

    g_plot->plotLayout()->setAlignCanvasToScale( QwtAxis::XBottom, true );
    g_plot->plotLayout()->setAlignCanvasToScale( QwtAxis::YLeft, false );

    g_plot->plotLayout()->setCanvasMargin( 0 );
    g_plot->updateCanvasMargins();

    g_plot->replot();

    g_plot->setAutoReplot( true );
}

MultiBarChartWidget::~MultiBarChartWidget()
{
    delete ui;
}

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