IText 使用 XML Worker 防止跨多个页面的行划分

1 回答

• 8

  .NET 开发人员，但您应该能够轻松翻译以下 C#代码。

  任何时候默认的 XML Worker 实现都不能满足您的需求，您基本上只需要查看源代码。首先，查看XML Worker是否支持标签类中所需的标记。有一个很好的<table>实现支持page-break-inside:avoid样式，但它只能在<table>级别工作**，而不是行<tr>级别。幸运的是，覆盖表的End()方法并不是那么多。

  如果不支持标记，则需要通过继承AbstractTagProcessor来滚动自己的自定义标记处理器，但不是为了这个答案而去那里。

  无论如何，对代码。不是通过改变page-break-inside:avoid样式的行为来吹走默认实现，我们可以使用自定义HTML属性并充分利用两个世界：

  public class TableProcessor : Table
  {
      // custom HTML attribute to keep <tr> on same page if possible
      public const string NO_ROW_SPLIT = "no-row-split";
      public override IList<IElement> End(IWorkerContext ctx, Tag tag, IList<IElement> currentContent)
      {
          IList<IElement> result = base.End(ctx, tag, currentContent);
          var table = (PdfPTable)result[0];
  
          if (tag.Attributes.ContainsKey(NO_ROW_SPLIT))
          {
              // if not set,  table **may** be forwarded to next page
              table.KeepTogether = false;
              // next two properties keep <tr> together if possible
              table.SplitRows = true;
              table.SplitLate = true;
          }
          return new List<IElement>() { table };
      }
  }
  

  并且生成一些测试的简单方法HTML：

  public string GetHtml()
  {
      var html = new StringBuilder();
      var repeatCount = 15;
      for (int i = 0; i < repeatCount; ++i) { html.Append("<h1>h1</h1>"); }
  
      var text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer vestibulum sollicitudin luctus. Curabitur at eros bibendum, porta risus a, luctus justo. Phasellus in libero vulputate, fermentum ante nec, mattis magna. Nunc viverra viverra sem, et pulvinar urna accumsan in. Quisque ultrices commodo mauris, et convallis magna. Duis consectetur nisi non ultrices dignissim. Aenean imperdiet consequat magna, ac ornare magna suscipit ac. Integer fermentum velit vitae porttitor vestibulum. Morbi iaculis sed massa nec ultricies. Aliquam efficitur finibus dolor, et vulputate turpis pretium vitae. In lobortis lacus diam, ut varius tellus varius sed. Integer pulvinar, massa quis feugiat pulvinar, tortor nisi bibendum libero, eu molestie est sapien quis odio. Lorem ipsum dolor sit amet, consectetur adipiscing elit.";
  
      // default iTextSharp.tool.xml.html.table.Table (AbstractTagProcessor)
      // is at the <table>, **not <tr> level
      html.Append("<table style='page-break-inside:avoid;'>");
      html.AppendFormat(
          @"<tr><td style='border:1px solid #000;'>DEFAULT IMPLEMENTATION</td>
              <td style='border:1px solid #000;'>{0}</td></tr>",
          text
      );
      html.Append("</table>");
  
      // overriden implementation uses a custom HTML attribute to keep:
      // <tr> together - see TableProcessor
      html.AppendFormat("<table {0}>", TableProcessor.NO_ROW_SPLIT);
      for (int i = 0; i < repeatCount; ++i)
      {
          html.AppendFormat(
              @"<tr><td style='border:1px solid #000;'>{0}</td>
              <td style='border:1px solid #000;'>{1}</td></tr>",
              i, text
          );
      }
      html.Append("</table>");
      return html.ToString();
  }
  

  最后是解析代码：

  using (var stream = new FileStream(OUTPUT_FILE, FileMode.Create))
  {
      using (var document = new Document())
      {
          PdfWriter writer = PdfWriter.GetInstance(
              document, stream
          );
          document.Open();
  
          // instantiate custom tag processor and add to `HtmlPipelineContext`.
          var tagProcessorFactory = Tags.GetHtmlTagProcessorFactory();
          tagProcessorFactory.AddProcessor(
              new TableProcessor(),
              new string[] { HTML.Tag.TABLE }
          );
          var htmlPipelineContext = new HtmlPipelineContext(null);
          htmlPipelineContext.SetTagFactory(tagProcessorFactory);
  
          var pdfWriterPipeline = new PdfWriterPipeline(document, writer);
          var htmlPipeline = new HtmlPipeline(htmlPipelineContext, pdfWriterPipeline);
  
          var cssResolver = XMLWorkerHelper.GetInstance().GetDefaultCssResolver(true);
          var cssResolverPipeline = new CssResolverPipeline(
              cssResolver, htmlPipeline
          );
  
          var worker = new XMLWorker(cssResolverPipeline, true);
          var parser = new XMLParser(worker);
          using (var stringReader = new StringReader(GetHtml()))
          {
              parser.Parse(stringReader);
          }
      }
  }
  

  完整来源.

  维护默认实现 - 首先将<table>保持在一起，而不是分成两页：

  

  自定义实现在第二个<table>中保持行：

  

  回复于 2024-04-20T04:33:21+08:00