Qwt QwtScaleDraw自定义坐标轴

1.概述

QwtScaleDraw 是 Qt 绘图库 Qwt 中的一个类，用于绘制坐标轴刻度线和刻度标签。它提供了一些方法和属性来设置刻度线和标签的样式、布局和对齐方式。

以下是类继承关系：

2.常用方法

标签相关方法：

setLabelRotation(double angle)：设置标签旋转角度。
setLabelAlignment(Alignment alignment)：设置标签对齐方式。

刻度线相关设置：

void setTickLength (QwtScaleDiv::TickType, double length)：设置刻度线长度

自定义标签，重写label方法

virtual QwtText label (double) const

3.示例

自定义下x轴的坐标轴。

#ifndef BARCHARTSINGLEWIDGET_H
#define BARCHARTSINGLEWIDGET_H

#include <QWidget>

namespace Ui {
class BarChartSingleWidget;
}

class BarChartSingleWidget : public QWidget
{
    Q_OBJECT

public:
    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 )
    {
        //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;
};

//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 bar

        setSpacing( 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 );

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

    g_plot->replot();

    // 显示绘图对象
    ui->verticalLayout->addWidget(g_plot);
}

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