Qwt QwtPlotBarChart自定义条形统计图

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1.概述

QwtPlotBarChart 是 Qt 绘图库 Qwt 中的一个类，用于绘制柱状图。它可以将数据通过柱形的高度来展示，方便比较不同数据量的大小差别。QwtPlotBarChart 类提供了一些方法和属性来设置柱形的样式、颜色、边界等。

以下是类的继承关系图：

2. 常用方法

设置数据：

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

自定义条形统计图，需重写函数：

virtual QwtColumnSymbol * specialSymbol (int sampleIndex, const QPointF &) const
virtual QwtText barTitle (int sampleIndex) const

设置间距：

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

设置方向：

void setOrientation (Qt::Orientation)

设置基线：

void setBaseline (double)

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

3.示例

示例1：一个简单的条形统计图

可以明显看见效果很差，坐标轴不美观，条形图没有颜色外观。

#include "BarChartSingleWidget.h"
#include "ui_BarChartSingleWidget.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"static QwtPlot *g_plot = nullptr;BarChartSingleWidget::BarChartSingleWidget(QWidget *parent) :QWidget(parent),ui(new Ui::BarChartSingleWidget)
{ui->setupUi(this);//设置plot背景色g_plot = new QwtPlot(QwtText("XX学校学生人数统计"),this);g_plot->setAutoFillBackground( true );g_plot->setPalette( QColor( "Linen" ) );//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 );// 创建数据QVector<double> data;data << 10 << 20 << 30 << 40;// 创建柱状图QwtPlotBarChart *barChart = new QwtPlotBarChart();// 将数据设置到柱状图上barChart->setSamples(data);// 将柱状图添加到绘图对象中barChart->attach(g_plot);// 显示绘图对象ui->verticalLayout->addWidget(g_plot);
}BarChartSingleWidget::~BarChartSingleWidget()
{delete ui;
}

示例2：自定义条形统计图

增加bar颜色，自定义坐标轴。

首先自定义bar继承QwtPlotBarChart类，重写specialSymbol和barTitle方法。

然后自定义坐标轴继承QwtScaleDraw类，重写label方法。

#ifndef BARCHARTSINGLEWIDGET_H
#define BARCHARTSINGLEWIDGET_H#include <QWidget>namespace Ui {
class BarChartSingleWidget;
}class BarChartSingleWidget : public QWidget
{Q_OBJECTpublic:explicit BarChartSingleWidget(QWidget *parent = 0);~BarChartSingleWidget();private:Ui::BarChartSingleWidget *ui;QStringList m_distros;
};#endif // BARCHARTSINGLEWIDGET_H#include "BarChartSingleWidget.h"
#include "ui_BarChartSingleWidget.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"//自定义坐标轴
class ScaleDraw : public QwtScaleDraw
{public:ScaleDraw( Qt::Orientation orientation, const QStringList& labels ): m_labels( labels ){setTickLength( QwtScaleDiv::MinorTick, 0 );setTickLength( QwtScaleDiv::MediumTick, 0 );setTickLength( QwtScaleDiv::MajorTick, 2 );enableComponent( QwtScaleDraw::Backbone, false );if ( orientation == Qt::Vertical ){setLabelRotation( -60.0 );}else{setLabelRotation( -20.0 );}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;
};//自定义ChartItem类,实现specialSymbol和barTitle方法
class ChartItem : public QwtPlotBarChart
{public:ChartItem(): QwtPlotBarChart( "Page Hits" ){setLegendMode( QwtPlotBarChart::LegendBarTitles );setLegendIconSize( QSize( 10, 14 ) );setLayoutPolicy( AutoAdjustSamples );setLayoutHint( 4.0 ); // minimum width for a single barsetSpacing( 10 ); // spacing between bars}void addDistro( const QString& distro, const QColor& color ){m_colors += color;m_distros += distro;itemChanged();}virtual QwtColumnSymbol* specialSymbol(int index, const QPointF& ) const QWT_OVERRIDE{// we want to have individual colors for each bar//新建一个标记QwtColumnSymbol* symbol = new QwtColumnSymbol( QwtColumnSymbol::Box );symbol->setLineWidth( 2 );  //设置线宽symbol->setFrameStyle( QwtColumnSymbol::Raised );//设置边框风格QColor c( Qt::white );if ( index >= 0 && index < m_colors.size() )c = m_colors[ index ];//设置颜色symbol->setPalette( c );return symbol;}//设置bar的标题virtual QwtText barTitle( int sampleIndex ) const QWT_OVERRIDE{QwtText title;if ( sampleIndex >= 0 && sampleIndex < m_distros.size() )title = m_distros[ sampleIndex ];return title;}private:QList< QColor > m_colors;       //每个bar的颜色QList< QString > m_distros;     //每个bar的标题
};static QwtPlot *g_plot = nullptr;BarChartSingleWidget::BarChartSingleWidget(QWidget *parent) :QWidget(parent),ui(new Ui::BarChartSingleWidget)
{ui->setupUi(this);const struct{const char* distro;const int hits;QColor color;} pageHits[] ={{ "一年级", 1114, QColor( "DodgerBlue" ) },{ "二年级", 1373, QColor( "#d70751" ) },{ "三年级", 1638, QColor( "SteelBlue" ) },{ "四年级", 1395, QColor( "Indigo" ) },{ "五年级", 3874, QColor( 183, 255, 183 ) },{ "六年级", 1532, QColor( 115, 186, 37 ) },{ "七年级", 1059, QColor( "LightSkyBlue" ) },{ "八年级", 2391, QColor( "FireBrick" ) }};//设置plot背景色g_plot = new QwtPlot(QwtText("XX学校学生人数统计"),this);g_plot->setAutoFillBackground( true );g_plot->setPalette( QColor( "Linen" ) );//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 );// 创建柱状图ChartItem* chartItem = new ChartItem();//设置条形图数据QVector< double > samples;for ( uint i = 0; i < sizeof( pageHits ) / sizeof( pageHits[ 0 ] ); i++ ){m_distros += pageHits[ i ].distro;samples += pageHits[ i ].hits;chartItem->addDistro( pageHits[ i ].distro, pageHits[ i ].color );}chartItem->setSamples( samples );chartItem->attach( g_plot );//设置坐标轴//设置自定义的坐标轴g_plot->setAxisTitle( QwtAxis::XBottom, "年级" );g_plot->setAxisMaxMinor( QwtAxis::XBottom, 3 );g_plot->setAxisScaleDraw( QwtAxis::XBottom, new ScaleDraw( Qt::Vertical, m_distros ) );g_plot->setAxisTitle( QwtAxis::YLeft, "人数" );g_plot->setAxisMaxMinor( QwtAxis::YLeft, 3 );//设置自定义的坐标轴QwtScaleDraw* scaleDraw = new QwtScaleDraw();scaleDraw->setTickLength( QwtScaleDiv::MediumTick, 4 );g_plot->setAxisScaleDraw( QwtAxis::YLeft, scaleDraw );g_plot->plotLayout()->setCanvasMargin( 0 );g_plot->replot();// 显示绘图对象ui->verticalLayout->addWidget(g_plot);
}BarChartSingleWidget::~BarChartSingleWidget()
{delete ui;
}