如何在 Apache POI 中重用字体？

Question

每次调用 "workbook.createFont()" 都会向工作簿添加一种新字体。有没有方便的方法来重复使用这些字体？

显然，我可以在程序中重复使用字体对象。但是当我重新打开 Java 程序时，我需要一种方法来取回 Font 对象。

虽然可以使用 "workbook.getNumberOfFonts()" 和 "workbook.getFontAt(i)"，但使用这些方法并不是很方便。

我的解决方法：
我在创建字体的时候添加了一个CustomProperty，里面保存着字体对应的编号。

Map<String, Font> fonts = new HashMap<>();

CustomProperties customProps  = workbook.getProperties().getCustomProperties(); 

if(customProps.contains("arial_12_b")) {
    short index = customProps.getProperty("arial_12_b").getI2();
    fonts.put("arial_12_b", workbook.getFontAt(index));
} else {                                
    Font font = workbook.createFont();
    font.setFontName("Arial");
    font.setFontHeightInPoints((short)12);
    font.setBold(true);

    customProps.addProperty("arial_12_b", font.getIndex());

    fonts.put("arial_12_b", font);
}

CellStyle 通过 CellUtil class 解决了同样的问题，它检查 CellStyle 是否已经存在，如果不存在则创建它。有没有类似字体的东西？

此致
阿福

Answer 1

可以提供一种使用 Workbook.findFont to achieve what you are asking about. To be much like CellUtil.setCellStyleProperties 的方法，它可以使用 Map<FontProperty, Object> fontproperties 来设置字体属性，其中 FontProperty 是所有属性的枚举 Workbook.findFont目前检查。现在是粗体、颜色、FONTHEIGHT、FONTNAME、ITALIC、删除线、TYPEOFFSET、下划线。

示例：

 //method for getting current font from cell
 private static Font getFont(Cell cell) {
  Workbook wb = cell.getRow().getSheet().getWorkbook();
  CellStyle style = cell.getCellStyle();
  return wb.getFontAt(style.getFontIndex());
 }

 private enum FontProperty {
  BOLD, COLOR, FONTHEIGHT, FONTNAME, ITALIC, STRIKEOUT, TYPEOFFSET, UNDERLINE
 }

 //method for getting font having special settings additional to given source font
 private static Font getFont(Workbook wb, Font fontSrc, Map<FontProperty, Object> fontproperties) {
  boolean isBold = fontSrc.getBold();
  short color = fontSrc.getColor();
  short fontHeight = fontSrc.getFontHeight();
  String fontName = fontSrc.getFontName();
  boolean isItalic = fontSrc.getItalic();
  boolean isStrikeout = fontSrc.getStrikeout();
  short typeOffset = fontSrc.getTypeOffset();
  byte underline = fontSrc.getUnderline();

  for (FontProperty property : fontproperties.keySet()) {
   switch (property) {
    case BOLD:
     isBold = (boolean)fontproperties.get(property);
    break;
    case COLOR:
     color = (short)fontproperties.get(property);
    break;
    case FONTHEIGHT:
     fontHeight = (short)fontproperties.get(property);
    break;
    case FONTNAME:
     fontName = (String)fontproperties.get(property);
    break;
    case ITALIC:
     isItalic = (boolean)fontproperties.get(property);
    break;
    case STRIKEOUT:
     isStrikeout = (boolean)fontproperties.get(property);
    break;
    case TYPEOFFSET:
     typeOffset = (short)fontproperties.get(property);
    break;
    case UNDERLINE:
     underline = (byte)fontproperties.get(property);
    break;
   }
  }

  Font font = wb.findFont(isBold, color, fontHeight, fontName, isItalic, isStrikeout, typeOffset, underline);
  if (font == null) {
   font = wb.createFont();
   font.setBold(isBold);
   font.setColor(color);
   font.setFontHeight(fontHeight);
   font.setFontName(fontName);
   font.setItalic(isItalic);
   font.setStrikeout(isStrikeout);
   font.setTypeOffset(typeOffset);
   font.setUnderline(underline);
  }

  return font;
 }

在此代码中，Workbook.findFont 用于尝试查找已具有所有属性的字体。仅当未找到 (if (font == null)) 时才会创建新字体。

使用方法：

  //set new cell D6 having special font settings
  row = CellUtil.getRow(5, sheet);
  cell = CellUtil.getCell(row, 3);
  fontproperties = new HashMap<FontProperty, Object>();
  fontproperties.put(FontProperty.BOLD, true);
  fontproperties.put(FontProperty.COLOR, IndexedColors.BLUE.getIndex());
  fontproperties.put(FontProperty.FONTHEIGHT, (short)(20*20));
  fontproperties.put(FontProperty.FONTNAME, "Courier New");
  fontproperties.put(FontProperty.STRIKEOUT, true);
  fontproperties.put(FontProperty.UNDERLINE, Font.U_DOUBLE);
  font = getFont(wb, getFont(cell), fontproperties);
  styleproperties = new HashMap<String, Object>();
  styleproperties.put(CellUtil.FONT, font.getIndex());
  CellUtil.setCellStyleProperties(cell, styleproperties);
  cell.setCellValue("new cell");

有关完整示例，请参阅 How to format Excel Cell as Date in Apache POI。

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