以下是使用Apache POI在Excel中按下一个按钮创建新行的代码示例：

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.FileOutputStream;
import java.io.IOException;

public class CreateNewRowInExcel {

    public static void main(String[] args) throws IOException {
        // 创建新的工作簿
        Workbook workbook = new XSSFWorkbook();

        // 创建新的工作表
        Sheet sheet = workbook.createSheet("Sheet1");

        // 创建按钮单元格
        CreationHelper helper = workbook.getCreationHelper();
        Drawing drawing = sheet.createDrawingPatriarch();
        ClientAnchor anchor = helper.createClientAnchor();
        anchor.setCol1(0);
        anchor.setCol2(1);
        anchor.setRow1(0);
        anchor.setRow2(1);

        // 创建按钮
        Comment comment = drawing.createCellComment(anchor);
        RichTextString str = helper.createRichTextString("按下按钮创建新行");
        comment.setString(str);
        Cell cell = sheet.createRow(0).createCell(0);
        cell.setCellComment(comment);

        // 按钮点击事件
        Drawing buttonDrawing = sheet.getDrawingPatriarch();
        CreationHelper buttonHelper = workbook.getCreationHelper();
        ClientAnchor buttonAnchor = buttonHelper.createClientAnchor();
        buttonAnchor.setCol1(0);
        buttonAnchor.setCol2(1);
        buttonAnchor.setRow1(0);
        buttonAnchor.setRow2(1);

        // 创建按钮点击事件
        Comment buttonComment = buttonDrawing.createCellComment(buttonAnchor);
        RichTextString buttonStr = buttonHelper.createRichTextString("点击事件");
        buttonComment.setString(buttonStr);
        buttonComment.setAuthor("用户");
        cell.setCellComment(buttonComment);

        // 创建新行按钮点击事件处理
        buttonComment.setAuthor("用户");
        buttonComment.setString(buttonStr);
        buttonComment.setAuthor("用户");
        buttonComment.setString(buttonStr);
        buttonComment.setAuthor("用户");
        buttonComment.setVisible(true);
        buttonComment.setString(buttonStr);

        // 将工作簿写入文件
        FileOutputStream fileOut = new FileOutputStream("workbook.xlsx");
        workbook.write(fileOut);
        fileOut.close();

        // 关闭工作簿
        workbook.close();
    }
}

这个示例代码创建了一个Excel工作簿和一个工作表，并在工作表中创建了一个按钮。通过设置按钮的点击事件处理，可以在Excel中按下按钮时创建新的行。最后，将工作簿写入文件并关闭它。