itext添加標題（heading）

標題即是在文檔在大綱里的目錄分級。

itext 2.7之后才有了該功能。

具體實現方式如下：

            FONT_PROJECT = RtfParagraphStyle.STYLE_HEADING_1;

            FONT_APPLICATION = RtfParagraphStyle.STYLE_HEADING_2;

            FONT_TYPE = RtfParagraphStyle.STYLE_HEADING_3;

com.lowagie.text.rtf.style.RtfParagraphStyle類繼承自RtfFont，RtfFont又繼承自Font。

它為Paragraph提供Style，使用方式和Font一致。

RtfParagraphStyle.STYLE_HEADING_1

該常量為RtfParagraphStyle的一個默認實現，表示第一級標題。

我們來看看它的實現：

    /**
     * The style for level 1 headings.
     */
    public static final RtfParagraphStyle STYLE_HEADING_1 = new RtfParagraphStyle("heading 1", "Normal");
    /**
     * The style for level 2 headings.
     */
    public static final RtfParagraphStyle STYLE_HEADING_2 = new RtfParagraphStyle("heading 2", "Normal");
    /**
     * The style for level 3 headings.
     */
    public static final RtfParagraphStyle STYLE_HEADING_3 = new RtfParagraphStyle("heading 3", "Normal");

注意第一個參數"heading 1"，這是rtf的json屬性值之一，它生產的json文件會包括如下部分：

{

{\style\s3 \ql\fi0\li0\ri0\f2\fs32\b\i\cf0 heading 3;}
{\style\s2 \ql\fi0\li0\ri0\f2\fs32\b\cf0 heading 2;}
{\style\s1 \ql\fi0\li0\ri0\f2\fs40\b\cf0 heading 1;}

}

這就是rtf本身的標題定義，了解了這些，我們就能用

STYLE_HEADING_1

STYLE_HEADING_2

STYLE_HEADING_3 

來定制三級菜單了。

示例:

public class HeadingTest {
    public static void main(String[] args) throws FileNotFoundException,
            DocumentException {
        String file = "C:\\Users\\my\\Desktop\\dome2.doc";
        Document document = new Document(PageSize.A4);
　　　　 RtfWriter2.getInstance(document,new FileOutputStream(file));
        document.open();
        
        document.add(new Paragraph("1", RtfParagraphStyle.STYLE_HEADING_1));
        document.add(new Paragraph("2", RtfParagraphStyle.STYLE_HEADING_2));
        document.add(new Paragraph("3", RtfParagraphStyle.STYLE_HEADING_3));
        document.close();
        System.out.println("DONE!");
    }
}

如果要生成多級標題呢？要稍微復雜點，假如我們參照 STYLE_HEADING_1 的寫法來自定義一段：

RtfParagraphStyle heading_4 = new RtfParagraphStyle("heading 4",
                "Normal");

很快我們就會發現，會跑出一個NullPointException
原因在於，所有的RtfParagraphStyle都是被RtfDocumentHeader的RtfStylesheetList里所維護的

我們需要在RtfStylesheetList里注冊我們自定義的這個heading_4。

實現方式如下：

 

RtfWriter2 writer = RtfWriter2.getInstance(document,
                new FileOutputStream(file));
        document.open();
        RtfDocumentSettings settings = writer.getDocumentSettings();
        RtfParagraphStyle heading_4 = new RtfParagraphStyle("heading 4",
                "Normal");
        settings.registerParagraphStyle(heading_4);

完成注冊后，該RtfParagraphStyle就可以正常使用了

對之前的示例代碼進行一點修改：

public class HeadingTest {
    public static void main(String[] args) throws FileNotFoundException,
            DocumentException {
        String file = "C:\\Users\\gateway\\Desktop\\dome2.doc";
        Document document = new Document(PageSize.A4);
        RtfWriter2 writer = RtfWriter2.getInstance(document,
                new FileOutputStream(file));
        document.open();
        RtfDocumentSettings settings = writer.getDocumentSettings();
        RtfParagraphStyle heading_4 = new RtfParagraphStyle("heading 4",
                "Normal");
        RtfParagraphStyle heading_5 = new RtfParagraphStyle("heading 5",
                "Normal");
        settings.registerParagraphStyle(heading_4);
        settings.registerParagraphStyle(heading_5);
        
        document.add(new Paragraph("1", RtfParagraphStyle.STYLE_HEADING_1));
        document.add(new Paragraph("2", RtfParagraphStyle.STYLE_HEADING_2));
        document.add(new Paragraph("3", RtfParagraphStyle.STYLE_HEADING_3));
        document.add(new Paragraph("4", heading_4));
        document.add(new Paragraph("5", heading_5));
        document.close();
        System.out.println("DONE!");
    }
}

實現效果如圖所示：