直方图效果图如下

main.cpp代码 如下：

#include qapplication.h

#include qmainwindow.h

#include qtoolbar.h

#include qtoolbutton.h

#include qcombobox.h

#include barchart.h

class MainWindow: public QMainWindow

{

public:

MainWindow( QWidget * = NULL );

private:

BarChart *d_chart;

};

MainWindow::MainWindow( QWidget *parent ):

QMainWindow( parent )

{

d_chart = new BarChart( this );

setCentralWidget( d_chart );

QToolBar *toolBar = new QToolBar( this );

QComboBox *orientationBox = new QComboBox( toolBar );

orientationBox-addItem( Vertical );

orientationBox-addItem( Horizontal );

orientationBox-setSizePolicy( QSizePolicy::Fixed, QSizePolicy::Fixed );

QToolButton *btnExport = new QToolButton( toolBar );

btnExport-setText( Export );

btnExport-setToolButtonStyle( Qt::ToolButtonTextUnderIcon );

connect( btnExport, SIGNAL( clicked() ), d_chart, SLOT( exportChart() ) );

toolBar-addWidget( orientationBox );

toolBar-addWidget( btnExport );

addToolBar( toolBar );

d_chart-setOrientation( orientationBox-currentIndex() );

connect( orientationBox, SIGNAL( currentIndexChanged( int ) ),

d_chart, SLOT( setOrientation( int ) ) );

}

int main( int argc, char **argv )

{

QApplication a( argc, argv );

MainWindow mainWindow;

mainWindow.resize( 600, 400 );

mainWindow.show();

return a.exec();

}

barchart.h文件如下：

#ifndef _BAR_CHART_H_

#include qwt_plot.h

#include qstringlist.h

class DistroChartItem;

class BarChart: public QwtPlot

{

Q_OBJECT

public:

BarChart( QWidget * = NULL );

public Q_SLOTS:

void setOrientation( int );

void exportChart();

private:

void populate();

DistroChartItem *d_barChartItem;//自定义直方图类

QStringList d_distros;//改变方向重置标题用

};

#endif

barchat.cpp代码如下：

#include barchart.h

#include qwt_plot_renderer.h

#include qwt_plot_canvas.h

#include qwt_plot_barchart.h

#include qwt_column_symbol.h

#include qwt_plot_layout.h

#include qwt_legend.h

#include qwt_scale_draw.h

class DistroScaleDraw: public QwtScaleDraw

{

public:

DistroScaleDraw( Qt::Orientation orientation, const QStringList labels ):

d_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 );

}

//刻度标签值

virtual QwtText label( double value ) const

{

QwtText lbl;

const int index = qRound( value );//四舍五入

if ( index = 0 index = d_labels.size() )

{

lbl = d_labels;

}

return lbl;

}

private:

const QStringList d_labels;

};

//直方图

//QwtPlotBarChart将一系列数据显示为bar

class DistroChartItem: public QwtPlotBarChart

{

public:

DistroChartItem():

QwtPlotBarChart( Page Hits )

{

setLegendMode( QwtPlotBarChart::LegendBarTitles );//显示所有bar各自的标题，而QwtPlotBarChart::LegendChartTitle 显示这个表的标题

setLegendIconSize( QSize( 10, 14 ) );

}

//分配颜色和标题给bar，并更新

void addDistro( const QString distro, const QColor color )

{

d_colors += color;

d_distros += distro;

itemChanged();//Update the legend of the parent plot.

}

//自定义每个Bar

virtual QwtColumnSymbol *specialSymbol(

int index, const QPointF ) const

{

QwtColumnSymbol *symbol = new QwtColumnSymbol( QwtColumnSymbol::Box );

symbol-setLineWidth( 1 );

symbol-setFrameStyle( QwtColumnSymbol::Plain );//Raised

QColor c( Qt::white );

if ( index = 0 index d_colors.size() )

c = d_colors;

symbol-setPalette( c );

return symbol;

}

//自定义每个bar的标题

virtual QwtText barTitle( int sampleIndex ) const

{

QwtText title;

if ( sampleIndex = 0 sampleIndex d_distros.size() )

title = d_distros;

return title;

}

private:

QListQColor d_colors;

QListQString d_distros;

};

BarChart::BarChart( QWidget *parent ):

QwtPlot( parent )

{

const struct

{

const char *distro;

const int hits;

QColor color;

} pageHits =

{

{ Arch, 1114, QColor( DodgerBlue ) },

{ Debian, 1373, QColor( #d70751 ) },

{ Fedora, 1638, QColor( SteelBlue ) },

{ Mageia, 1395, QColor( Indigo ) },

{ Mint, 3874, QColor( 183, 255, 183 ) },

{ openSuSE, 1532, QColor( 115, 186, 37 ) },

{ Puppy, 1059, QColor( LightSkyBlue ) },

{ Ubuntu, 2391, QColor( FireBrick ) }

};

setAutoFillBackground( true );

setPalette( QColor( Linen ) );

//设置画布

QwtPlotCanvas *canvas = new QwtPlotCanvas();

canvas-setLineWidth( 2 );

canvas-setFrameStyle( QFrame::Box | QFrame::Sunken );

canvas-setBorderRadius( 10 );

QPalette canvasPalette( QColor( Plum ) );

canvasPalette.setColor( QPalette::Foreground, QColor( Indigo ) );

canvas-setPalette( canvasPalette );

setCanvas( canvas );

setTitle( DistroWatch Page Hit Ranking, April 2012 );

d_barChartItem = new DistroChartItem();

//数据源

QVector double samples;

for ( uint i = 0; i sizeof( pageHits ) / sizeof( pageHits ); i++ )

{

d_distros += pageHits.distro; //给标题赋值

samples += pageHits.hits;//给数据赋值

d_barChartItem-addDistro(

pageHits.distro, pageHits.color );//更新颜色和标题

}

d_barChartItem-setSamples( samples );//更新数据

d_barChartItem-attach( this );

insertLegend( new QwtLegend() );

setOrientation( 0 );

setAutoReplot( false );

}

void BarChart::setOrientation( int o )

{

const Qt::Orientation orientation =

( o == 0 ) ? Qt::Vertical : Qt::Horizontal;

int axis1 = QwtPlot::xBottom;

int axis2 = QwtPlot::yLeft;

if ( orientation == Qt::Horizontal )

qSwap( axis1, axis2 );

d_barChartItem-setOrientation( orientation );//直方图方向

d_barChartItem-setSpacing( 20 );//spacing 是两个样本之间的距离（两个直方图之间的距离，或者每组直方图之间的距离

d_barChartItem-setMargin( 30);// margin 最外层的直方图与画布的边框矩形之间的距离

setAxisTitle( axis1, Distros );

setAxisMaxMinor( axis1, 3);//设置坐标轴小刻度的最大值

setAxisMaxMajor( axis1, 10);//设置坐标轴大刻度的最大值

setAxisScaleDraw( axis1, new DistroScaleDraw( orientation, d_distros ) );//需要重新更新标题

setAxisTitle( axis2, Hits per day ( HPD ) );

setAxisMaxMinor( axis2, 3 );

QwtScaleDraw *scaleDraw = new QwtScaleDraw();

scaleDraw-setTickLength( QwtScaleDiv::MediumTick, 4 );

setAxisScaleDraw( axis2, scaleDraw );

plotLayout()-setCanvasMargin( 0 );

replot();

}

void BarChart::exportChart()

{

QwtPlotRenderer renderer;

renderer.exportTo( this, distrowatch.pdf );

}