是否可以更改条形颜色？
我编写了一个简单的计数程序。
我还想实现一件事：如果计数大于 200，则使用蓝色绘制条形。如果没有，请使用黄色。
目前，所有条形颜色均为红色。
所以我想问一下，可以改变bar的颜色吗？
如果是，有人可以给我一些指导来实现吗？
提前致谢！
附件是我的编码：
<%@page contentType="text/html"%>
<%@page import="java.io.*" %>
<%@page import="java.sql.*" %>
<%@page import="org.jfree.data.category.*" %>
<%@page import="org.jfree.chart.*" %>
<%@page import="org.jfree.chart.plot.*" %>
<html>
<body>
<%
DefaultCategoryDataset dataset = new DefaultCategoryDataset();
try
{
Class.forName("com.mysql.jdbc.Driver");
java.sql.Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/delivery","root","root");
Statement sta = con.createStatement();
ResultSet res = sta.executeQuery("SELECT inventory, subject from statistics");
int count;
String subject;
while (res.next())
{
count = res.getInt("inventory");
subject = res.getString("subject");
dataset.addValue(count,"enrollment count statistics", subject);
}
}
catch (Exception e) {
System.err.println(e.getMessage());
}
JFreeChart bar = ChartFactory.createBarChart("Enrollment Chart", "subject","Count",dataset, PlotOrientation.HORIZONTAL,true, false, false);
//BarRenderer renderer = (BarRenderer) bar.getCategoryPlot().getRenderer();
String fileName = "/bar.png";
String file = application.getRealPath("/") + fileName;
try
{
FileOutputStream fileOut = new FileOutputStream(file);
ChartUtilities.writeChartAsPNG(fileOut, bar, 300, 300);
}
catch (IOException e)
{
out.print(e);
}
%>
<img src="/delivery/bar.png" alt="subject Bar Chart" />
</body>
</html>
神奇的是getItemPaint(int,int) 方法 http://www.jfree.org/jfreechart/api/gjdoc/org/jfree/chart/renderer/AbstractRenderer.html#getItemPaint%3aint%3aint of the 条形渲染器类 http://www.jfree.org/jfreechart/api/javadoc/org/jfree/chart/renderer/category/BarRenderer.html.
一个例子是在http://javabeanz.wordpress.com/2007/07/04/creating-barcharts-with-custom-colours-using-jfreechart/ http://javabeanz.wordpress.com/2007/07/04/creating-barcharts-with-custom-colours-using-jfreechart/
你想要做的事情是这样的：
class CustomRenderer extends BarRenderer
{
public CustomRenderer()
{
}
public Paint getItemPaint(final int row, final int column)
{
// returns color depending on y coordinate.
return (row > 200) ? Color.blue : Color.yellow ;
}
}
然后在调用 ChartFactory.createBarChart 之后，您会执行
final CategoryPlot plot = chart.getCategoryPlot();
CategoryItemRenderer renderer = new CustomRenderer();
plot.setRenderer(renderer);
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