DocumentViewer到RichTextBox绑定错误

Question

我有一个RichTextBox和DocumentViewer (放在TabControl中)的应用程序，我想做一些类似于“热预览”的东西。我已经将DocumentViewer.Document属性绑定到RichTextBox.Document

具有约束力：

<DocumentViewer Document="{Binding Document, Converter={StaticResource FlowDocumentToPaginatorConverter}, ElementName=mainRTB, Mode=OneWay}" />

这是转换器代码：

 public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            FlowDocument d = value as FlowDocument;
            DocumentPaginator pagin = ((IDocumentPaginatorSource)d).DocumentPaginator;
            FixedDocumentSequence result = null;
            Size s = new Size(793.700787402, 1122.519685039);
            pagin.PageSize = s;

            using (MemoryStream ms = new MemoryStream())
            {
                TextRange tr = new TextRange(d.ContentStart, d.ContentEnd);
                tr.Save(ms, DataFormats.XamlPackage);
                Package p = Package.Open(ms, FileMode.Create, FileAccess.ReadWrite);
                Uri uri = new Uri(@"memorystream://doc.xps");
                PackageStore.AddPackage(uri, p);
                XpsDocument xpsDoc = new XpsDocument(p);
                xpsDoc.Uri = uri;
                XpsDocument.CreateXpsDocumentWriter(xpsDoc).Write(pagin);
                result = xpsDoc.GetFixedDocumentSequence();
            }
            return result;
        }

当我启动这个应用程序时，一切都正常，直到我用DocumentViewer切换到选项卡为止。应用程序崩溃了，我得到了这样的例外：

不能在只写模式下执行读操作.

我做错什么了？有可能把这个绑起来吗？

Answer 1

错误信息确实是令人困惑的，原因也不是很清楚。基本上，您正在过早关闭包含MemoryStream的XpsDocument，而当DocumentViewer试图读取文档时，由于它是只写模式(因为流已经关闭)，它不能打开。

解决方案是，在MemoryStream完成查看之后，在之前不立即关闭。为了实现这一点，我编写了一个返回XpsDocumentConverter的XpsReference。

此外，由于您从未能够转换和显示单个XpsDocument，因此您还不会遇到在PackageStore中使用同一个Uri的多个包的下一个问题。我在下面的实施中已经处理了这一点。

public static XpsDocumentReference CreateXpsDocument(FlowDocument document)
{            
    // Do not close the memory stream as it still being used, it will be closed 
    // later when the XpsDocumentReference is Disposed.
    MemoryStream ms = new MemoryStream();

    // We store the package in the PackageStore
    Uri uri = new Uri(String.Format("pack://temp_{0}.xps/", Guid.NewGuid().ToString("N")));
    Package pkg = Package.Open(ms, FileMode.Create, FileAccess.ReadWrite);
    PackageStore.AddPackage(uri, pkg);
    XpsDocument xpsDocument = new XpsDocument(pkg, CompressionOption.Normal, uri.AbsoluteUri);

    // Need to force render the FlowDocument before pagination. 
    // HACK: This is done by *briefly* showing the document.
    DocumentHelper.ForceRenderFlowDocument(document);

    XpsSerializationManager rsm = new XpsSerializationManager(new XpsPackagingPolicy(xpsDocument), false);
    DocumentPaginator paginator = new FixedDocumentPaginator(document, A4PageDefinition.Default);            
    rsm.SaveAsXaml(paginator);

    return new XpsDocumentReference(ms, xpsDocument);
}

public class XpsDocumentReference : IDisposable
{
    private MemoryStream MemoryStream;            
    public XpsDocument XpsDocument { get; private set; }
    public FixedDocument FixedDocument { get; private set; }

    public XpsDocumentReference(MemoryStream ms, XpsDocument xpsDocument)
    {
        MemoryStream = ms;
        XpsDocument = xpsDocument;

         DocumentReference reference = xpsDocument.GetFixedDocumentSequence().References.FirstOrDefault();
         if (reference != null)
             FixedDocument = reference.GetDocument(false);
    }

    public void Dispose()
    {
        Package pkg = PackageStore.GetPackage(XpsDocument.Uri);
        if (pkg != null)
        {
            pkg.Close();
            PackageStore.RemovePackage(XpsDocument.Uri);
        }

        if (MemoryStream != null)
        {
            MemoryStream.Dispose();
            MemoryStream = null;
        }
    }

}

XpsReference实现了IDisposable，所以请记住在上面调用Dispose()。

而且，一旦您解决了上述错误，您可能遇到的下一个问题将是内容不像您所期望的那样呈现。这是由于您需要克隆FlowDocument，并且它还没有经过一个完整的度量和布局传递。阅读Printing BlockUIContainer to XpsDocument/FixedDocument关于如何解决这一问题。