16.6 實例應用 · JFreeChart 開發者指南

## 16.6 實例應用首先，需要創建一個圖表，我們創建一個時序圖，代碼如下： ``` XYDataset dataset = createDataset(); JFreeChart chart = ChartFactory.createTimeSeriesChart( "Legal & General Unit Trust Prices", "Date", "Price Per Unit", dataset, true, true, false ); ``` 這里沒有任何的特殊代碼——事實上，我們可以使用創建JFreeChart的其他對象替代上面的代碼。下一步，我們將在一個PDF文件中保存一個圖表的副本： ``` File fileName = new File(System.getProperty("user.home") + "/jfreechart1.pdf"); saveChartAsPDF(fileName, chart, 400, 300, new DefaultFontMapper()); ``` 下面有一些需要注意的問題：首先，PDF文件名稱是硬編碼完成的，不能修改。主要是在演示中，減少代碼量。在實際應用中，我們需要提供一些讓用戶指定文件名稱與路徑的方式，比如彈出一個文件選擇對話框。其次，saveChartAsPDF()方法還未實現。為了創建這個方法，我們先創建另一個更通用的writeChartAsPDF().方法。該方法執行saveChartAsPDF()方法需要的全部工作。但該方法的輸入參數是一個文件輸出流而不是一個文件，代碼如下： ``` public static void writeChartAsPDF(OutputStream out, JFreeChart chart, int width, int height, FontMapper mapper) throws IOException { Rectangle pagesize = new Rectangle(width, height); Document document = new Document(pagesize, 50, 50, 50, 50); try { PdfWriter writer = PdfWriter.getInstance(document, out); document.addAuthor("JFreeChart"); document.addSubject("Demonstration"); document.open(); PdfContentByte cb = writer.getDirectContent(); PdfTemplate tp = cb.createTemplate(width, height); Graphics2D g2 = tp.createGraphics(width, height, mapper); Rectangle2D r2D = new Rectangle2D.Double(0, 0, width, height); chart.draw(g2, r2D); g2.dispose(); cb.addTemplate(tp, 0, 0); } catch (DocumentException de) { System.err.println(de.getMessage()); } document.close(); } ``` 在上面代碼的方法里面，我們看到一些創建和代碼iText文檔的代碼，從文檔中獲得了一個Graphics2D實例，使用Graphics2D對象畫出這個圖表，并關閉了這個文檔。同時我們也注意到方法的一個參數是FontMapper對象。iText使用FontMapper接口將java字體對象映射成基本的字體對象。DefaultFontMapper類預先默認映射為java本地化字體。如果你希望用這些字體，使用DefaultFontMapper構建缺省的對象即可，如果你相使用其他的字體（例如，支持一個特殊的字符集），那么我們需要做一些額外的工作。本章后面將有介紹。在writeChartAsPDF()方法的實現里面，我們創建了一個自定義頁面尺寸大小（匹配字符的需要尺寸）的PDF文檔。我們提前設置了改變了字符的尺寸、位置并且在PDF文檔中畫出多個字符，以適應不同的頁面尺寸。現在我們將使用saveChartAsPDF()方法很容易的實現了將一個PDF數據發送到一個數據流上。建化了創建文件輸出流的過程，并且將該對象傳給了writeChartAsPDF()方法。代碼如下： ``` public static void saveChartAsPDF(File file, JFreeChart chart, int width, int height, FontMapper mapper) throws IOException { OutputStream out = new BufferedOutputStream(new FileOutputStream(file)); writeChartAsPDF(out, chart, width, height, mapper); out.close(); } ``` 上面的每一步代碼都是必須的。上面的代碼組合成全部的代碼如下（整個工程的代碼都在這里，以便我們可以看到所有的聲明和內容）： ``` package demo; import java.awt.Graphics2D; import java.awt.geom.Rectangle2D; import java.io.BufferedOutputStream; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.OutputStream; import java.text.SimpleDateFormat; import org.jfree.chart.ChartFactory; import org.jfree.chart.JFreeChart; import org.jfree.chart.axis.DateAxis; import org.jfree.chart.plot.XYPlot; import org.jfree.chart.renderer.xy.XYLineAndShapeRenderer; import org.jfree.data.time.Month; import org.jfree.data.time.TimeSeries; import org.jfree.data.time.TimeSeriesCollection; import org.jfree.data.xy.XYDataset; import com.lowagie.text.Document; import com.lowagie.text.DocumentException; import com.lowagie.text.Rectangle; import com.lowagie.text.pdf.DefaultFontMapper; import com.lowagie.text.pdf.FontMapper; import com.lowagie.text.pdf.PdfContentByte; import com.lowagie.text.pdf.PdfTemplate; import com.lowagie.text.pdf.PdfWriter; /** * A simple demonstration showing how to write a chart to PDF format using * JFreeChart and iText. * <P> * You can download iText from http://www.lowagie.com/iText. */ public class PDFExportDemo1 { /** * Saves a chart to a PDF file. * * @param file * the file. * @param chart * the chart. * @param width * the chart width. * @param height * the chart height. */ public static void saveChartAsPDF(File file, JFreeChart chart, int width, int height, FontMapper mapper) throws IOException { OutputStream out = new BufferedOutputStream(new FileOutputStream(file)); writeChartAsPDF(out, chart, width, height, mapper); out.close(); } /** * Writes a chart to an output stream in PDF format. * * @param out * the output stream. * @param chart * the chart. * @param width * the chart width. * @param height * the chart height. * */ public static void writeChartAsPDF(OutputStream out, JFreeChart chart, int width, int height, FontMapper mapper) throws IOException { Rectangle pagesize = new Rectangle(width, height); Document document = new Document(pagesize, 50, 50, 50, 50); try { PdfWriter writer = PdfWriter.getInstance(document, out); document.addAuthor("JFreeChart"); document.addSubject("Demonstration"); document.open(); PdfContentByte cb = writer.getDirectContent(); PdfTemplate tp = cb.createTemplate(width, height); Graphics2D g2 = tp.createGraphics(width, height, mapper); Rectangle2D r2D = new Rectangle2D.Double(0, 0, width, height); chart.draw(g2, r2D); g2.dispose(); cb.addTemplate(tp, 0, 0); } catch (DocumentException de) { System.err.println(de.getMessage()); } document.close(); } /** * Creates a dataset, consisting of two series of monthly data. * * * * @return the dataset. */ public static XYDataset createDataset() { TimeSeries s1 = new TimeSeries("L&G European Index Trust", Month.class); s1.add(new Month(2, 2001), 181.8); s1.add(new Month(3, 2001), 167.3); s1.add(new Month(4, 2001), 153.8); s1.add(new Month(5, 2001), 167.6); s1.add(new Month(6, 2001), 158.8); s1.add(new Month(7, 2001), 148.3); s1.add(new Month(8, 2001), 153.9); s1.add(new Month(9, 2001), 142.7); s1.add(new Month(10, 2001), 123.2); s1.add(new Month(11, 2001), 131.8); s1.add(new Month(12, 2001), 139.6); s1.add(new Month(1, 2002), 142.9); s1.add(new Month(2, 2002), 138.7); s1.add(new Month(3, 2002), 137.3); s1.add(new Month(4, 2002), 143.9); s1.add(new Month(5, 2002), 139.8); s1.add(new Month(6, 2002), 137.0); s1.add(new Month(7, 2002), 132.8); TimeSeries s2 = new TimeSeries("L&G UK Index Trust", Month.class); s2.add(new Month(2, 2001), 129.6); s2.add(new Month(3, 2001), 123.2); s2.add(new Month(4, 2001), 117.2); s2.add(new Month(5, 2001), 124.1); s2.add(new Month(6, 2001), 122.6); s2.add(new Month(7, 2001), 119.2); s2.add(new Month(8, 2001), 116.5); s2.add(new Month(9, 2001), 112.7); s2.add(new Month(10, 2001), 101.5); s2.add(new Month(11, 2001), 106.1); s2.add(new Month(12, 2001), 110.3); s2.add(new Month(1, 2002), 111.7); s2.add(new Month(2, 2002), 111.0); s2.add(new Month(3, 2002), 109.6); s2.add(new Month(4, 2002), 113.2); s2.add(new Month(5, 2002), 111.6); s2.add(new Month(6, 2002), 108.8); s2.add(new Month(7, 2002), 101.6); TimeSeriesCollection dataset = new TimeSeriesCollection(); dataset.addSeries(s1); dataset.addSeries(s2); return dataset; } public static void main(String[] args) { try { // create a chart... XYDataset dataset = createDataset(); JFreeChart chart = ChartFactory.createTimeSeriesChart( "Legal & General Unit Trust Prices", "Date", "Price Per Unit", dataset, true, true, false); // some additional chart customisation here... XYPlot plot = chart.getXYPlot(); XYLineAndShapeRenderer renderer = (XYLineAndShapeRenderer) plot .getRenderer(); renderer.setShapesVisible(true); DateAxis axis = (DateAxis) plot.getDomainAxis(); axis.setDateFormatOverride(new SimpleDateFormat("MMM-yyyy")); // write the chart to a PDF file... File fileName = new File(System.getProperty("user.home") + "/jfreechart1.pdf"); System.out.println(fileName.getPath()); saveChartAsPDF(fileName, chart, 400, 300, new DefaultFontMapper()); } catch (IOException e) { System.out.println(e.getMessage()); } } } ``` 在你完成和運行上面的應用之前，記得修改PDF文件的名稱以滿足我們的要求。同時前面16.5節提到的jar也必須在我們的classpath中。.