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## 7.2 使用categoryDataset数据集创建折线图 ### 7.2.1 概述 使用CategoryDataset创建的折线图将每个数据点(种类,值)使用一条直线连接起来。本章讲的一个简单应用产生如下界面,如图7.1: ![](img/jfc37789.png) 图7.1 一个简单的折线图 全部的代码简JFreeChart开发指南一并下载的demo(参考:LineChartDemo1.java)。 ### 7.2.2 CategoryDataset 正如其他图表一样,创建折线图的第一步是创建第一个dataset。在本例子中,使用DefaultCategoryDataset,代码如下: ``` private static CategoryDataset createDataset() { DefaultCategoryDataset defaultcategorydataset = new DefaultCategoryDataset(); defaultcategorydataset.addValue(212.0, "Classes", "JDK 1.0"); defaultcategorydataset.addValue(504.0, "Classes", "JDK 1.1"); defaultcategorydataset.addValue(1520.0, "Classes", "JDK 1.2"); defaultcategorydataset.addValue(1842.0, "Classes", "JDK 1.3"); defaultcategorydataset.addValue(2991.0, "Classes", "JDK 1.4"); defaultcategorydataset.addValue(3500.0, "Classes", "JDK 1.5"); return defaultcategorydataset; } ``` 注意:你可以使用任何实现Category接口的数据集。 ### 7.2.3 创建图表 ChartFactory类提供了一个便利的方法createLineChart()创建折线图。代码如下: ``` JFreeChart jfreechart = ChartFactory.createLineChart( "Java Standard Class Library",// 图表标题 null, // 主轴标签 "Class Count",// 范围轴标签 categorydataset, // 数据集 PlotOrientation.VERTICAL,// 方向 false, // 是否包含图例 true, // 提示信息是否显示 false// 是否使用urls ); ``` 该方法构建了一个带有标题、图例、和相应的数轴和心态提示产生器的JFreeChart对象。创建Dataset数据集的过程见上节。 ### 7.2.4 定制图表 折线图表将使用大部分缺省的属性来进行初始化。当然了,我们也可以随意修改折线图的属性,来改变我们图表的外观。在本例中,我们通过下面的方式定制折线图: + 在图表上添加两个副标题; + 图表的背景颜色设成白色; + 图区背景颜色设成亮灰色; + 网格线颜色改变成白色; + 范围轴修改成仅显示整数数值; + renderer使用白色填充的形状。 首先,将副标题添加在缺省的位置(主标题下方),代码如下: ``` jfreechart.addSubtitle(new TextTitle("Number of Classes By Release")); ``` 第二个副标题加入了一些额外的代码,来改变字体,并放置在图表的下方,并且靠右对其,代码如下: ``` TextTitle texttitle = (new TextTitle("Source: Java In A Nutshell (5th Edition) by David Flanagan (O'Reilly)")); texttitle.setFont(new Font("SansSerif", 0, 10)); texttitle.setPosition(RectangleEdge.BOTTOM); texttitle.setHorizontalAlignment(HorizontalAlignment.RIGHT); jfreechart.addSubtitle(texttitle); ``` 改变图表的背景颜色非常简单,因为JFreeChart类就有设置背景颜色的属性。代码如下: ``` //改变图表的背景颜色 jfreechart.setBackgroundPaint(Color.white); ``` 如果改变其他属性的,则需要首先获得图表CategoryPlot对象的引用,然后对该引用进行相应属性的设置。获得对象引用的代码如下: ``` CategoryPlot categoryplot = (CategoryPlot) jfreechart.getPlot(); ``` 使用CategoryPlot设置图区的背景颜色为亮灰色,设置网格线颜色为白色的代码如下: ``` categoryplot.setBackgroundPaint(Color.lightGray); categoryplot.setRangeGridlinePaint(Color.white); ``` 图区负责在图表上画出数据和轴。其中一部分工作由renderer来完成,我们可以通过getRender()来获得一个renderer。renderer维护大部分与图表内数据项的显示相关的属性。代码如下: ``` LineAndShapeRenderer renderer = (LineAndShapeRenderer) categoryplot.getRenderer(); renderer.setShapesVisible(true); renderer.setDrawOutlines(true); renderer.setUseFillPaint(true); ``` 同时图区也管理着图表所有的轴。在本实例中,修改范围轴以便范围轴的刻度标签显示为整数值。 ``` NumberAxis rangeAxis = (NumberAxis) categoryplot.getRangeAxis(); rangeAxis.setStandardTickUnits(NumberAxis.createIntegerTickUnits()); ``` 定制图表还有很多其他的方式。具体的内容详见本文档相关章节,API文档以及源代码实例。 ### 7.2.5 程序的全部代码 ``` /* ------------------- * LineChartDemo1.java * ------------------- * (C) Copyright 2002-2005, by Object Refinery Limited. * */ package demo; import java.awt.BasicStroke; import java.awt.Color; import java.awt.Dimension; import java.awt.Font; import java.awt.geom.Ellipse2D; import java.net.URL; import javax.swing.ImageIcon; import javax.swing.JPanel; import org.jfree.chart.ChartFactory; import org.jfree.chart.ChartPanel; import org.jfree.chart.JFreeChart; import org.jfree.chart.axis.NumberAxis; import org.jfree.chart.plot.CategoryPlot; import org.jfree.chart.plot.PlotOrientation; import org.jfree.chart.renderer.category.LineAndShapeRenderer; import org.jfree.chart.title.TextTitle; import org.jfree.data.category.CategoryDataset; import org.jfree.data.category.DefaultCategoryDataset; import org.jfree.ui.ApplicationFrame; import org.jfree.ui.HorizontalAlignment; import org.jfree.ui.RectangleEdge; import org.jfree.ui.RefineryUtilities; public class LineChartDemo1 extends ApplicationFrame { /** * */ private static final long serialVersionUID = -6354350604313079793L; /* synthetic */static Class class$demo$LineChartDemo1; public LineChartDemo1(String string) { super(string); JPanel jpanel = createDemoPanel(); jpanel.setPreferredSize(new Dimension(500, 270)); setContentPane(jpanel); } private static CategoryDataset createDataset() { DefaultCategoryDataset defaultcategorydataset = new DefaultCategoryDataset(); defaultcategorydataset.addValue(212.0, "Classes", "JDK 1.0"); defaultcategorydataset.addValue(504.0, "Classes", "JDK 1.1"); defaultcategorydataset.addValue(1520.0, "Classes", "JDK 1.2"); defaultcategorydataset.addValue(1842.0, "Classes", "JDK 1.3"); defaultcategorydataset.addValue(2991.0, "Classes", "JDK 1.4"); defaultcategorydataset.addValue(3500.0, "Classes", "JDK 1.5"); return defaultcategorydataset; } private static JFreeChart createChart(CategoryDataset categorydataset) { JFreeChart jfreechart = ChartFactory.createLineChart( "Java Standard Class Library",// 图表标题 null, // 主轴标签 "Class Count",// 范围轴标签 categorydataset, // 数据集 PlotOrientation.VERTICAL,// 方向 false, // 是否包含图例 true, // 提示信息是否显示 false// 是否使用urls ); // 添加主标题 jfreechart.addSubtitle(new TextTitle("Number of Classes By Release")); TextTitle texttitle = (new TextTitle( "Source: Java In A Nutshell (5th Edition) by David Flanagan (O'Reilly)")); texttitle.setFont(new Font("SansSerif", 0, 10)); texttitle.setPosition(RectangleEdge.BOTTOM); texttitle.setHorizontalAlignment(HorizontalAlignment.RIGHT); jfreechart.addSubtitle(texttitle); // 改变图表的背景颜色 jfreechart.setBackgroundPaint(Color.white); CategoryPlot categoryplot = (CategoryPlot) jfreechart.getPlot(); categoryplot.setBackgroundPaint(Color.lightGray); categoryplot.setRangeGridlinePaint(Color.white); categoryplot.setRangeGridlinesVisible(false); URL url = (class$demo$LineChartDemo1 == null ? class$demo$LineChartDemo1 = class$("demo.LineChartDemo1") : class$demo$LineChartDemo1).getClassLoader().getResource( "OnBridge11small.png"); if (url != null) { ImageIcon imageicon = new ImageIcon(url); jfreechart.setBackgroundImage(imageicon.getImage()); categoryplot.setBackgroundPaint(new Color(0, 0, 0, 0)); } NumberAxis numberaxis = (NumberAxis) categoryplot.getRangeAxis(); numberaxis.setStandardTickUnits(NumberAxis.createIntegerTickUnits()); LineAndShapeRenderer lineandshaperenderer = (LineAndShapeRenderer) categoryplot .getRenderer(); lineandshaperenderer.setShapesVisible(true); lineandshaperenderer.setDrawOutlines(true); lineandshaperenderer.setUseFillPaint(true); lineandshaperenderer.setBaseFillPaint(Color.white); lineandshaperenderer.setSeriesStroke(0, new BasicStroke(3.0F)); lineandshaperenderer.setSeriesOutlineStroke(0, new BasicStroke(2.0F)); lineandshaperenderer.setSeriesShape(0, new Ellipse2D.Double(-5.0, -5.0, 10.0, 10.0)); LineAndShapeRenderer renderer = (LineAndShapeRenderer) categoryplot .getRenderer(); renderer.setShapesVisible(true); renderer.setDrawOutlines(true); renderer.setUseFillPaint(true); return jfreechart; } public static JPanel createDemoPanel() { JFreeChart jfreechart = createChart(createDataset()); return new ChartPanel(jfreechart); } public static void main(String[] strings) { LineChartDemo1 linechartdemo1 = new LineChartDemo1( "JFreeChart - Line Chart Demo 1"); linechartdemo1.pack(); RefineryUtilities.centerFrameOnScreen(linechartdemo1); linechartdemo1.setVisible(true); } /* synthetic */ static Class class$(String string) { Class var_class; try { var_class = Class.forName(string); } catch (ClassNotFoundException classnotfoundexception) { throw new NoClassDefFoundError(classnotfoundexception.getMessage()); } return var_class; } } ```