使用 C# 的 PDF 工具提示

以下代码片段也适用于 Aspose.PDF.Drawing 库。

通过添加隐形按钮为搜索文本添加工具提示

通常需要为 PDF 文档中的短语或特定单词添加一些详细信息作为工具提示，以便在用户将鼠标光标悬停在文本上时弹出。Aspose.PDF for .NET 提供此功能，通过在搜索文本上添加隐形按钮来创建工具提示。以下代码片段将向您展示如何实现此功能：

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void AddTooltipToSearchedText()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_Text();

    // Create PDF document
    using (var document = new Aspose.Pdf.Document())
    {
        document.Pages.Add().Paragraphs.Add(new Aspose.Pdf.Text.TextFragment("Move the mouse cursor here to display a tooltip"));
        document.Pages[1].Paragraphs.Add(new Aspose.Pdf.Text.TextFragment("Move the mouse cursor here to display a very long tooltip"));
        // Save PDF document
        document.Save(dataDir + "Tooltip_out.pdf");
    }

    // Open PDF document
    using (var document = new Aspose.Pdf.Document(dataDir + "Tooltip_out.pdf"))
    {
        // Create TextAbsorber object to find all the phrases matching the regular expression
        var absorber = new Aspose.Pdf.Text.TextFragmentAbsorber("Move the mouse cursor here to display a tooltip");
        // Accept the absorber for the document pages
        document.Pages.Accept(absorber);
        // Get the extracted text fragments
        var textFragments = absorber.TextFragments;

        // Loop through the fragments
        foreach (var fragment in textFragments)
        {
            // Create invisible button on text fragment position
            var field = new Aspose.Pdf.Forms.ButtonField(fragment.Page, fragment.Rectangle);
            // AlternateName value will be displayed as tooltip by a viewer application
            field.AlternateName = "Tooltip for text.";
            // Add button field to the document
            document.Form.Add(field);
        }

        absorber = new Aspose.Pdf.Text.TextFragmentAbsorber("Move the mouse cursor here to display a very long tooltip");
        document.Pages.Accept(absorber);
        textFragments = absorber.TextFragments;

        foreach (var fragment in textFragments)
        {
            var field = new Aspose.Pdf.Forms.ButtonField(fragment.Page, fragment.Rectangle);
            // Set very long text
            field.AlternateName = "Lorem ipsum dolor sit amet, consectetur adipiscing elit," +
                                    " sed do eiusmod tempor incididunt ut labore et dolore magna" +
                                    " aliqua. Ut enim ad minim veniam, quis nostrud exercitation" +
                                    " ullamco laboris nisi ut aliquip ex ea commodo consequat." +
                                    " Duis aute irure dolor in reprehenderit in voluptate velit" +
                                    " esse cillum dolore eu fugiat nulla pariatur. Excepteur sint" +
                                    " occaecat cupidatat non proident, sunt in culpa qui officia" +
                                    " deserunt mollit anim id est laborum.";
            document.Form.Add(field);
        }

        // Save PDF document
        document.Save(dataDir + "Tooltip_out.pdf");
    }
}

关于工具提示的长度，工具提示文本作为 PDF 字符串类型包含在 PDF 文档中，位于内容流之外。对于 PDF 文件中的此类字符串没有有效的限制（请参见 PDF 参考附录 C.）。然而，符合标准的阅读器（例如 Adobe Acrobat）在特定处理器和特定操作环境下确实有这样的限制。请参考您的 PDF 阅读器应用程序文档。

创建隐藏文本块并在鼠标悬停时显示

在 Aspose.PDF 中，隐藏操作的功能实现了在某些隐形按钮上鼠标进入/退出时显示/隐藏文本框字段（或任何其他类型的注释）。为此，使用 Aspose.Pdf.Annotations.HideAction 类将隐藏/显示的操作分配给文本块。请使用以下代码片段在鼠标进入/退出时显示/隐藏文本块。

请注意，文档中的 PDF 操作在符合标准的阅读器（例如 Adobe Reader）中运行良好，但对其他 PDF 阅读器（例如网页浏览器插件）没有保证。我们进行了简要调查并发现：

• PDF 文档中所有隐藏操作的实现都在 Internet Explorer v.11.0 中运行良好。
• 所有隐藏操作的实现也在 Opera v.12.14 中运行，但我们发现文档首次打开时有一些响应延迟。
• 仅使用接受字段名称的 HideAction 构造函数的实现可以在 Google Chrome v.61.0 浏览文档时正常工作；如果在 Google Chrome 中浏览很重要，请使用相应的构造函数：

buttonField.Actions.OnEnter = new HideAction(floatingField.FullName, false); buttonField.Actions.OnExit = new HideAction(floatingField.FullName);

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void CreateHiddenTextBlock()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_Text();

    // Create PDF document
    using (var document = new Aspose.Pdf.Document())
    {
        // Add paragraph with text
        document.Pages.Add().Paragraphs.Add(new Aspose.Pdf.Text.TextFragment("Move the mouse cursor here to display floating text"));
        // Save PDF document
        document.Save(dataDir + "TextBlock_HideShow_MouseOverOut_out.pdf");
    }

    // Open PDF document
    using (var document = new Aspose.Pdf.Document(dataDir + "TextBlock_HideShow_MouseOverOut_out.pdf"))
    {
        // Create TextAbsorber object to find all the phrases matching the regular expression
        var absorber = new Aspose.Pdf.Text.TextFragmentAbsorber("Move the mouse cursor here to display floating text");
        // Accept the absorber for the document pages
        document.Pages.Accept(absorber);
        // Get the first extracted text fragment
        var textFragments = absorber.TextFragments;
        var fragment = textFragments[1];

        // Create hidden text field for floating text in the specified rectangle of the page
        var floatingField = new Aspose.Pdf.Forms.TextBoxField(fragment.Page, new Aspose.Pdf.Rectangle(100, 700, 220, 740));
        // Set text to be displayed as field value
        floatingField.Value = "This is the \"floating text field\".";
        // We recommend to make field 'readonly' for this scenario
        floatingField.ReadOnly = true;
        // Set 'hidden' flag to make field invisible on document opening
        floatingField.Flags |= Aspose.Pdf.Annotations.AnnotationFlags.Hidden;

        // Setting a unique field name isn't necessary but allowed
        floatingField.PartialName = "FloatingField_1";

        // Setting characteristics of field appearance isn't necessary but makes it better
        floatingField.DefaultAppearance = new Aspose.Pdf.Annotations.DefaultAppearance("Helv", 10, System.Drawing.Color.Blue);
        floatingField.Characteristics.Background = System.Drawing.Color.LightBlue;
        floatingField.Characteristics.Border = System.Drawing.Color.DarkBlue;
        floatingField.Border = new Aspose.Pdf.Annotations.Border(floatingField);
        floatingField.Border.Width = 1;
        floatingField.Multiline = true;

        // Add text field to the document
        document.Form.Add(floatingField);

        // Create invisible button on text fragment position
        var buttonField = new Aspose.Pdf.Forms.ButtonField(fragment.Page, fragment.Rectangle);
        // Create new hide action for specified field (annotation) and invisibility flag
        // (You also may reffer floating field by the name if you specified it above)
        // Add actions on mouse enter/exit at the invisible button field
        buttonField.Actions.OnEnter = new Aspose.Pdf.Annotations.HideAction(floatingField, false);
        buttonField.Actions.OnExit = new Aspose.Pdf.Annotations.HideAction(floatingField);

        // Add button field to the document
        document.Form.Add(buttonField);

        // Save PDF document
        document.Save(dataDir + "CreateHiddenTextBlock_out.pdf");
    }
}