程式扎記: [ Java 常見問題 ] JFreeChart: Apply a color to a single bar of single series graph

來源自這裡
Question:
In my chart I only have one serie, and I would like -according to the value- to set a different color for the bar. For exemple :

0-20 -> RED, 20-80 -> YELLOW, 80-100 -> GREEN

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CategoryPlot plot = chart.getCategoryPlot();  
CategoryDataset dataset = plot.getDataset(0);  
  
Number value = dataset.getValue(dataset.getRowKey(0), dataset.getColumnKey(0));  
Double val = value.doubleValue();  
  
if (val <= 20.0) {  
    BarRenderer renderer = (BarRenderer) plot.getRenderer();  
    Paint tmp = renderer.getItemPaint(row, column);  
  
    /* 
    ** Help Please 
    */        
}  
  
return chart;  

This is where I reached, I am then blocked and don't know really where to go. I saw in the documentation that Paint is an interface but none of the class implementing this interface does provide a setXXX() method. So my two question are :
1. How do I set a color to a single Bar ?
2. How do I apply that to my chart ?

Answer:
You'll need to create your own subclass of BarRenderer and override getItemPaint(). Instead of choosing a color based on column, choose it based on your value. Here's an outline to show how the existing BarRenderer works.

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plot.setRenderer(new MyRender());  
...  
class MyRender extends BarRenderer {  
  
    @Override  
    public Paint getItemPaint(int row, int col) {  
        System.out.println(row + " " + col + " " + super.getItemPaint(row, col));  
        return super.getItemPaint(row, col);  
    }  
}  

Example:
底下範例將 Bar Chart 定義下面的數值範圍使用不同的顏色顯示:

* <100: br="" green="" nbsp="">* 100~2xx: Yellow
* 3xx~4xx: Orange
* >499: Red

- BarChartDemo5.java

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package charts.bar.category;  
  
import java.awt.Color;  
import java.awt.Dimension;  
import java.awt.Font;  
import java.awt.Paint;  
import java.util.ArrayList;  
import java.util.List;  
  
import javax.swing.JPanel;  
  
import org.jfree.chart.ChartFactory;  
import org.jfree.chart.ChartPanel;  
import org.jfree.chart.JFreeChart;  
import org.jfree.chart.axis.AxisLocation;  
import org.jfree.chart.axis.CategoryAxis;  
import org.jfree.chart.axis.NumberAxis;  
import org.jfree.chart.labels.StandardCategoryItemLabelGenerator;  
import org.jfree.chart.plot.CategoryPlot;  
import org.jfree.chart.plot.PlotOrientation;  
import org.jfree.chart.renderer.category.BarRenderer;  
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.RefineryUtilities;  
  
// https://code.google.com/p/test-chart/source/browse/trunk/src/main/java/es/efor/plandifor/demo/BarChartDemo5.java?r=2  
public class BarChartDemo5 extends ApplicationFrame  
{  
    public static List Values = new ArrayList();  
    public BarChartDemo5(String s)  
    {  
            super(s);  
            JPanel jpanel = createDemoPanel();  
            jpanel.setPreferredSize(new Dimension(600, 400));  
            setContentPane(jpanel);  
    }  
  
    private static CategoryDataset createDataset()  
    {  
            DefaultCategoryDataset defaultcategorydataset = new DefaultCategoryDataset();  
            String s = "Prison Population Rates";  
            defaultcategorydataset.addValue(59D, s, "Norway"); Values.add(59D);  
            defaultcategorydataset.addValue(69D, s, "Switzerland"); Values.add(69D);  
            defaultcategorydataset.addValue(85D, s, "France"); Values.add(85D);  
            defaultcategorydataset.addValue(93D, s, "Syria"); Values.add(93D);  
            defaultcategorydataset.addValue(96D, s, "Germany"); Values.add(96D);  
            defaultcategorydataset.addValue(111D, s, "China"); Values.add(111D);  
            defaultcategorydataset.addValue(116D, s, "Australia"); Values.add(116D);  
            defaultcategorydataset.addValue(121D, s, "Egypt"); Values.add(121D);  
            defaultcategorydataset.addValue(129D, s, "England & Wales"); Values.add(129D);  
            defaultcategorydataset.addValue(157D, s, "New Zealand"); Values.add(157D);  
            defaultcategorydataset.addValue(205D, s, "Chile"); Values.add(205D);  
            defaultcategorydataset.addValue(229D, s, "Iran"); Values.add(229D);  
            defaultcategorydataset.addValue(359D, s, "Singapore"); Values.add(359D);  
            defaultcategorydataset.addValue(404D, s, "South Africa"); Values.add(404D);  
            defaultcategorydataset.addValue(406D, s, "Ukraine"); Values.add(406D);  
            defaultcategorydataset.addValue(686D, s, "USA"); Values.add(686D);  
            return defaultcategorydataset;  
    }  
  
      
    private static JFreeChart createChart(CategoryDataset categorydataset)  
    {  
            JFreeChart jfreechart = ChartFactory.createBarChart("Prison Population Rates - Selected Countries", "Country", "Prisoners Per 100,000 National Population", categorydataset, PlotOrientation.HORIZONTAL, true, true, false);  
            jfreechart.addSubtitle(new TextTitle("Source: http://www.homeoffice.gov.uk/rds/pdfs2/r188.pdf", new Font("Dialog", 2, 10)));  
            jfreechart.setBackgroundPaint(Color.white);  
            CategoryPlot categoryplot = (CategoryPlot)jfreechart.getPlot();  
            categoryplot.setBackgroundPaint(Color.lightGray);  
            categoryplot.setRangeGridlinePaint(Color.white);  
            categoryplot.setRangeAxisLocation(AxisLocation.BOTTOM_OR_LEFT);  
            MyRender barrenderer = new MyRender(Values);  
            //BarRenderer or = (BarRenderer)categoryplot.getRenderer();              
            categoryplot.setRenderer(barrenderer);  
            //barrenderer.setBaseItemLabelsVisible(true);  
            barrenderer.setBaseItemLabelGenerator(new StandardCategoryItemLabelGenerator());  
            CategoryAxis categoryaxis = categoryplot.getDomainAxis();  
            categoryaxis.setCategoryMargin(0.0D);  
            categoryaxis.setUpperMargin(0.02D);  
            categoryaxis.setLowerMargin(0.02D);  
            NumberAxis numberaxis = (NumberAxis)categoryplot.getRangeAxis();  
            numberaxis.setStandardTickUnits(NumberAxis.createIntegerTickUnits());  
            numberaxis.setUpperMargin(0.10000000000000001D);  
            return jfreechart;  
    }  
  
    public static JPanel createDemoPanel()  
    {  
            JFreeChart jfreechart = createChart(createDataset());  
            return new ChartPanel(jfreechart);  
    }  
  
    public static void main(String args[])  
    {  
            BarChartDemo5 barchartdemo5 = new BarChartDemo5("Bar Chart Demo 5");  
            barchartdemo5.pack();  
            RefineryUtilities.centerFrameOnScreen(barchartdemo5);  
            barchartdemo5.setVisible(true);  
    }  
      
    public static class MyRender extends BarRenderer {    
        List values;  
          
        public MyRender(List values){this.values = values;}  
            
        @Override    
        public Paint getItemPaint(int row, int col) {             
           double value = values.get(col);  
           int h = ((int)value)/100;  
           if(value<100) return Color.GREEN;  
           else if(h<3) return Color.yellow;  
           else if(h<5) return Color.orange;  
           else return Color.red;  
        }    
    }   
}  

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2014年6月10日星期二

[ Java 常見問題 ] JFreeChart: Apply a color to a single bar of single series graph

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