Java Apache POI 创建 Excel 双坐标轴折线图

本文介绍如何使用 Java 和 Apache POI 库创建带有双坐标轴的 Excel 折线图。

代码示例javaimport org.apache.poi.ss.usermodel.;import org.apache.poi.ss.util.CellRangeAddress;import org.apache.poi.xddf.usermodel.chart.;import org.apache.poi.xssf.usermodel.*;import org.openxmlformats.schemas.drawingml.x2006.chart.CTBoolean;import org.openxmlformats.schemas.drawingml.x2006.chart.CTLineSer;

import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.text.SimpleDateFormat;import java.util.Date;

public class ExcelChartExample04 {

public static void main(String[] args) {        try {            // 读取Excel文件            FileInputStream fileIn = new FileInputStream('input-1.xlsx');            XSSFWorkbook workbook = new XSSFWorkbook(fileIn);            XSSFSheet sheet1 = workbook.getSheet('P1');

        // 创建折线图            XSSFDrawing drawing = sheet1.createDrawingPatriarch();            XSSFClientAnchor anchor = drawing.createAnchor(0, 0, 0, 0, 0, 129, 10, 149);            XDDFChart chart = drawing.createChart(anchor);            chart.setTitleText('数据折线图');            chart.setTitleOverlay(false);

        // 设置图例位置            XDDFChartLegend legend = chart.getOrAddLegend();            legend.setPosition(LegendPosition.BOTTOM);

        // 设置横坐标轴为日期坐标轴            XDDFDataSource<?> dateSource = XDDFDataSourcesFactory.fromArray(new String[] {'A2:A127'});            XDDFDateAxis bottomAxis = chart.createDateAxis(AxisPosition.BOTTOM);            bottomAxis.setCrosses(AxisCrosses.AUTO_ZERO);            bottomAxis.setTitle('时间');            bottomAxis.setTickLabelPosition(AxisTickLabelPosition.NEXT_TO);

        // 设置时间格式            SimpleDateFormat dateFormat = new SimpleDateFormat('yyyy/MM/dd');            for (int i = 0; i < dateSource.getPointCount(); i++) {                Row row = sheet1.getRow(i + 1);                if (row != null) {                    Cell cell = row.getCell(0);                    if (cell != null && cell.getCellType() == CellType.NUMERIC) {                        Date date = cell.getDateCellValue();                        String formattedDate = dateFormat.format(date);                        cell.setCellValue(formattedDate);                    }                }            }

        // 设置左侧坐标轴为温度坐标轴            XDDFValueAxis leftAxis = chart.createValueAxis(AxisPosition.LEFT);            leftAxis.setCrosses(AxisCrosses.AUTO_ZERO);            leftAxis.setTitle('温度');

        // 设置右侧坐标轴为数值坐标轴            XDDFValueAxis rightAxis = chart.createValueAxis(AxisPosition.RIGHT);            rightAxis.setCrosses(AxisCrosses.MAX);            rightAxis.setTitle('数据值');

        // 设置数据源            XDDFNumericalDataSource<Double> xs1 = XDDFDataSourcesFactory.fromNumericCellRange(sheet1, new CellRangeAddress(1, 127, 2, 2));            XDDFNumericalDataSource<Double> ys1 = XDDFDataSourcesFactory.fromNumericCellRange(sheet1, new CellRangeAddress(1, 127, 0, 0));            XDDFNumericalDataSource<Double> ys2 = XDDFDataSourcesFactory.fromNumericCellRange(sheet1, new CellRangeAddress(1, 127, 1, 1));

        // 添加数据系列            XDDFLineChartData data = (XDDFLineChartData) chart.createData(ChartTypes.LINE, bottomAxis, leftAxis);            XDDFLineChartData.Series series1 = (XDDFLineChartData.Series) data.addSeries(xs1, ys1);            series1.setTitle('折线图1', null);            series1.setSmooth(false);            series1.setMarkerStyle(MarkerStyle.NONE);

        // 添加第二个数据系列            XDDFLineChartData.Series series2 = (XDDFLineChartData.Series) data.addSeries(xs1, ys2);            series2.setTitle('折线图2', null);            series2.setSmooth(false);            chart.getCTChart().getPlotArea().getLineChartArray(0).getSerArray(1).getOrder().setVal(1);

        // 设置次要垂直坐标轴            CTBoolean ctBoolean = CTBoolean.Factory.newInstance();            ctBoolean.setVal(false);            CTLineSer ctLineSer = chart.getCTChart().getPlotArea().getLineChartArray(0).getSerArray(1);            ctLineSer.addNewDLbls();            ctLineSer.getDLbls().setShowLegendKey(ctBoolean);            ctLineSer.getDLbls().setShowVal(ctBoolean);            ctLineSer.getDLbls().setShowCatName(ctBoolean);            ctLineSer.getDLbls().setShowSerName(ctBoolean);

        // 保存Excel文件            FileOutputStream fileOut = new FileOutputStream('input-1.xlsx');            workbook.write(fileOut);            fileOut.close();

        System.out.println('折线图已创建并保存到Excel文件中。');

    } catch (IOException e) {            e.printStackTrace();        }    }}

问题解决

在设置次要垂直坐标轴时，可能会遇到 NullPointerException 错误，这是因为 DLbls 对象为空。解决方法是在调用 getDLbls() 方法之前，先创建一个新的 DLbls 对象：java// 设置次要垂直坐标轴CTBoolean ctBoolean = CTBoolean.Factory.newInstance();ctBoolean.setVal(false);CTLineSer ctLineSer = chart.getCTChart().getPlotArea().getLineChartArray(0).getSerArray(1);ctLineSer.addNewDLbls(); // 创建新的 DLbls 对象ctLineSer.getDLbls().setShowLegendKey(ctBoolean);ctLineSer.getDLbls().setShowVal(ctBoolean);ctLineSer.getDLbls().setShowCatName(ctBoolean);ctLineSer.getDLbls().setShowSerName(ctBoolean);

总结

本文介绍了如何使用 Java 和 Apache POI 库创建带有双坐标轴的 Excel 折线图，并提供了解决常见问题的代码示例。希望对您有所帮助！