我正在寻找一种简洁的通用方法来描述 XAML FlowDocument 中重复的页眉和页脚，而无需任何代码。它只需要在从 C# 渲染到 XPS 时正确显示。
【问题讨论】：
标签： c# wpf xaml .net-4.0 flowdocument
几个月前我遇到了同样的问题，发现这些链接很有帮助： WPF Multipage Reports Part IV Pagination http://www.codeproject.com/KB/WPF/PimpedDocumentPaginator.aspx
我使用的基本技术是通过从DynamicDocumentPaginator 派生来创建自定义分页器，如下所示：
internal class HeaderFooterPaginator<THeaderModel, TFooterModel> : DynamicDocumentPaginator where THeaderModel : PageNumberModel, new() where TFooterModel : PageNumberModel, new()
{
...
}
在我的例子中，THeaderFooterModel 和 TFooterModel 是 PageNumberModel 类型的子类，因为我需要页眉或页脚才能显示当前页码。
public class PageNumberModel
{
public int PageNumber { get; set; }
}
自定义分页器委托原始 XPS 分页器完成大部分工作，因此将其存储在构造函数中。
THeaderModel 和 TFooterModel 类型允许分页器为每种类型检索 XAML DataTemplates，这允许您在 XAML 中指定页眉和页脚的布局，而无需求助于自定义绘图代码。
在我的代码中，页眉和页脚的大小是固定的，因此在创建分页器时，它会检索页眉和页脚模板以确定要保留多少空间。
在提供的链接中的示例代码中，他们为页眉和页脚保留空间的技术是使用缩放变换来缩小原始内容。相反，我告诉原始分页器使用减小的页面大小，然后将原始分页器生成的页面添加到ContainerVisual 并设置其Offset。如果页眉和页脚的大小是动态的，您可能无法执行此操作，因为页数会不断变化。
我记得的唯一其他复杂情况是，添加页眉和页脚时需要使用Dispatcher 队列（请参阅下面的AddHeaderOrFooterToContainerAsync）。否则数据绑定不起作用。我们稍微颠覆了 WPF 渲染模型以使其正常工作。
如果不包含代码，这一切都很难解释，所以我在下面附上了自定义渲染器代码。我已经删除了一些不相关的东西，所以如果它不能按原样编译，那可能就是原因:-)
请注意，传入页码偏移量是因为我们的 XPS 文档由多个 FlowDocument 部分组成，并且调用代码会跟踪当前的总页码。
希望这会有所帮助！
internal class HeaderFooterPaginator<THeaderModel, TFooterModel> : DynamicDocumentPaginator where THeaderModel : PageNumberModel, new() where TFooterModel : PageNumberModel, new()
{
private readonly double _footerHeight;
private readonly DataTemplate _footerTemplate;
private readonly double _headerHeight;
private readonly DataTemplate _headerTemplate;
private Size _newPageSize;
private Size _originalPageSize;
private readonly DynamicDocumentPaginator _originalPaginator;
private readonly int _pageNumberOffset;
private readonly FlowDocument _paginatorSource;
private const double HeaderAndFooterMarginHeight = 5;
private const double HeaderAndFooterMarginWidth = 10;
public HeaderFooterPaginator(int pageNumberOffset, FlowDocument document)
{
if (document == null)
{
throw new ArgumentNullException("document");
}
_paginatorSource = document;
if (_paginatorSource == null)
{
throw new InvalidOperationException("Could not create a clone of the document being paginated.");
}
_originalPaginator = ((IDocumentPaginatorSource) _paginatorSource).DocumentPaginator as DynamicDocumentPaginator;
if (_originalPaginator == null)
{
throw new InvalidOperationException("The paginator must be a DynamicDocumentPaginator.");
}
_headerTemplate = GetModelDataTemplate(typeof (THeaderModel));
_footerTemplate = GetModelDataTemplate(typeof (TFooterModel));
var headerSize = GetModelContentSize(new THeaderModel { PageNumber = int.MaxValue }, _headerTemplate, _originalPaginator.PageSize);
var footerSize = GetModelContentSize(new TFooterModel { PageNumber = int.MaxValue }, _footerTemplate, _originalPaginator.PageSize);
_headerHeight = double.IsInfinity(headerSize.Height) ? 0 : headerSize.Height;
_footerHeight = double.IsInfinity(footerSize.Height) ? 0 : footerSize.Height;
_pageNumberOffset = pageNumberOffset;
SetPageSize(new Size(document.PageWidth, document.PageHeight));
}
private void AddHeaderOrFooterToContainerAsync<THeaderOrFooter>(ContainerVisual container, double areaWidth, double areaHeight, Vector areaOffset, FrameworkTemplate template, int displayPageNumber) where THeaderOrFooter : PageNumberModel, new()
{
if (template == null)
{
return;
}
var visual = GetModelContent(new THeaderOrFooter { PageNumber = displayPageNumber }, template);
if (visual != null)
{
Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.ApplicationIdle, new Action(() =>
{
visual.Measure(_originalPageSize);
visual.Arrange(new Rect(0, 0, areaWidth, areaHeight));
visual.UpdateLayout();
var headerContainer = new ContainerVisual { Offset = areaOffset };
headerContainer.Children.Add(visual);
container.Children.Add(headerContainer);
}));
}
}
public override void ComputePageCount()
{
_originalPaginator.ComputePageCount();
}
private static void FlushDispatcher()
{
Dispatcher.CurrentDispatcher.Invoke(DispatcherPriority.ApplicationIdle, new DispatcherOperationCallback(delegate { return null; }), null);
}
private static FrameworkElement GetModelContent(object dataModel, FrameworkTemplate modelTemplate)
{
if (modelTemplate == null)
{
return null;
}
var content = modelTemplate.LoadContent() as FrameworkElement;
if (content == null)
{
return null;
}
content.DataContext = dataModel;
return content;
}
private static Size GetModelContentSize(object dataModel, FrameworkTemplate modelTemplate, Size availableSize)
{
var content = GetModelContent(dataModel, modelTemplate);
if (content == null)
{
return Size.Empty;
}
FlushDispatcher();
content.Measure(availableSize);
return content.DesiredSize;
}
private DataTemplate GetModelDataTemplate(Type modelType)
{
var key = new DataTemplateKey(modelType);
return _paginatorSource.TryFindResource(key) as DataTemplate;
}
public override ContentPosition GetObjectPosition(object value)
{
return _originalPaginator.GetObjectPosition(value);
}
public override DocumentPage GetPage(int pageNumber)
{
if (!_originalPaginator.IsPageCountValid)
{
ComputePageCount();
}
var originalPage = _originalPaginator.GetPage(pageNumber);
var newPage = new ContainerVisual();
var displayPageNumber = _pageNumberOffset + pageNumber;
var internalWidth = _originalPageSize.Width - 2*HeaderAndFooterMarginWidth;
AddHeaderOrFooterToContainerAsync<THeaderModel>(newPage, internalWidth, _headerHeight, new Vector(HeaderAndFooterMarginWidth, HeaderAndFooterMarginHeight), _headerTemplate, displayPageNumber);
var smallerPage = new ContainerVisual();
smallerPage.Children.Add(originalPage.Visual);
smallerPage.Offset = new Vector(HeaderAndFooterMarginWidth, HeaderAndFooterMarginHeight + _headerHeight);
newPage.Children.Add(smallerPage);
AddHeaderOrFooterToContainerAsync<TFooterModel>(newPage, internalWidth, _footerHeight, new Vector(HeaderAndFooterMarginWidth, _originalPageSize.Height - HeaderAndFooterMarginHeight - _footerHeight), _footerTemplate, displayPageNumber);
return new DocumentPage(newPage, _originalPageSize, originalPage.BleedBox, originalPage.ContentBox);
}
public override int GetPageNumber(ContentPosition contentPosition)
{
return _originalPaginator.GetPageNumber(contentPosition);
}
public override ContentPosition GetPagePosition(DocumentPage page)
{
return _originalPaginator.GetPagePosition(page);
}
private void SetPageSize(Size pageSize)
{
_originalPageSize = pageSize;
// Decrease the available page size by the height of the header and footer. The page is offset by the header height later on.
var sizeRect = new Rect(pageSize);
sizeRect.Inflate(-HeaderAndFooterMarginWidth, -(HeaderAndFooterMarginHeight + _footerHeight/2 + _headerHeight/2));
_originalPaginator.PageSize = _newPageSize = sizeRect.Size;
// Change page size of the document to the size of the content area
_paginatorSource.PageHeight = _newPageSize.Height;
_paginatorSource.PageWidth = _newPageSize.Width;
}
public override bool IsPageCountValid
{
get { return _originalPaginator.IsPageCountValid; }
}
public override int PageCount
{
get { return _originalPaginator.PageCount; }
}
public override Size PageSize
{
get { return _newPageSize; }
set { SetPageSize(value); }
}
public override IDocumentPaginatorSource Source
{
get { return _originalPaginator.Source; }
}
}
【讨论】：