具有相同UserControl实例的WPF FixedPage

Question

首先，我不确定标题的措辞是否正确。有通过ViewModel添加的UserControls，我通过搜索VisualTree找到它们并将它们添加到ObservableCollection<Grid>。我想做的是将我从VisualTree检索到的UserControl的每个实例打印到FixedDocument中，但每个UserControl都在一个页面上，直到它填满该页面并移动到下一页。

这是我当前打印按钮点击事件的代码：

private async void btnPrint_Click(object sender, RoutedEventArgs e)
{
try
{
if (tabMain.Items.Count > 0)
{
tab = new TabLayout();
tab.Payslip = new ObservableCollection<Grid>();

foreach (var grid in FindVisualChildren<Grid>(this))
{
if (grid.Name == "pdfFile")
{
tab.Payslip.Add(grid);
}
}
FrameworkElement toPrint = new FrameworkElement();
PrintDialog printDialog = new PrintDialog();
PrintCapabilities capabilities = printDialog.PrintQueue.GetPrintCapabilities(printDialog.PrintTicket);
Size pageSize = new Size(printDialog.PrintableAreaWidth, printDialog.PrintableAreaHeight);
Size visibleSize = new Size(capabilities.PageImageableArea.ExtentWidth, capabilities.PageImageableArea.ExtentHeight);
FixedDocument fixedDoc = new FixedDocument();

StackPanel panel = new StackPanel(); //was trying to stack them in a stackpanel first but it threw an exception about same instance of usercontrol blah blah...

foreach (var doc in tab.Payslip.ToList())
{
double yOffset = 0;
doc.Measure((new Size(double.PositiveInfinity, double.PositiveInfinity)));
doc.Arrange(new Rect(new Point(0, 0), doc.DesiredSize));
Size size = doc.DesiredSize;

while (yOffset < size.Height)
{
VisualBrush vb = new VisualBrush(doc);
vb.Stretch = Stretch.None;
vb.AlignmentX = AlignmentX.Left;
vb.AlignmentY = AlignmentY.Top;
vb.ViewboxUnits = BrushMappingMode.Absolute;
vb.TileMode = TileMode.None;
vb.Viewbox = new Rect(0, yOffset, visibleSize.Width, visibleSize.Height);
FixedPage page = new FixedPage();
PageContent pageContent = new PageContent();
((IAddChild)pageContent).AddChild(page);
fixedDoc.Pages.Add(pageContent);
page.Width = fixedDoc.DocumentPaginator.PageSize.Width;
page.Height = fixedDoc.DocumentPaginator.PageSize.Height;
Canvas canvas = new Canvas();
FixedPage.SetLeft(canvas, capabilities.PageImageableArea.OriginWidth);
FixedPage.SetTop(canvas, capabilities.PageImageableArea.OriginHeight);
canvas.Width = visibleSize.Width;
canvas.Height = visibleSize.Height;
canvas.Background = vb;
page.Children.Add(canvas);
yOffset += visibleSize.Height;
}
}
//printDialog.PrintDocument(fixedDoc.DocumentPaginator, "");
ShowPrintPreview(fixedDoc);
}
}
catch(Exception ex)
{
var exceptionDialog = new MessageDialog
{
Message = { Text = ex.ToString() }
};
await DialogHost.Show(exceptionDialog, "RootDialog");
}
}

当我尝试打印三个选项卡(UserControls托管在选项卡中)时，它是这样的：正如您在这里看到的，它打印三个单独的页面

我希望这三个标签都在一页上，如果我打印10个标签，那么它应该会填充第一页并进入下一页

上次我问类似的问题时，有人问我是否写了代码。这段代码的一部分来自StackOverflow上类似的FixedDocument问题，但它已经被编辑到对我实际有效的程度。所以，是的，我知道foreach中的FixedPage引用是导致创建三个单独页面的原因，我确实理解这段代码。

摘要：

我想知道的是，如何从每个Tab中获取UserControls，将其放到一个页面上，直到其满为止，而不会出现"指定的元素已经是另一个元素的逻辑子元素。请先断开连接。"错误。

Answer 1

我最终使用ItemsControl将Controls的ObservableCollection保存为列表，并使用此XpsDocumentWriter方法从ItemsControl打印。

public void PrintItemsTo(ItemsControl ic, String jobName)
{
PrintDialog dlg = new PrintDialog();
dlg.UserPageRangeEnabled = true;
if (dlg.ShowDialog().GetValueOrDefault())
{
PageRange range = dlg.PageRange;
//    range check - user selection starts from 1
if (range.PageTo > ic.Items.Count)
range.PageTo = ic.Items.Count;
dlg.PrintQueue.CurrentJobSettings.Description = jobName;
XpsDocumentWriter xdw = PrintQueue.CreateXpsDocumentWriter(dlg.PrintQueue);
if (dlg.UserPageRangeEnabled == false || range.PageTo < range.PageFrom)
WriteAllItems(ic, xdw);
else
WriteSelectedItems(ic, xdw, range);
}
}
private void WriteAllItems(ItemsControl ic, XpsDocumentWriter xdw)
{
PageRange range = new PageRange(1, ic.Items.Count);
WriteSelectedItems(ic, xdw, range);
}
private void WriteSelectedItems(ItemsControl ic, XpsDocumentWriter xdw, PageRange range)
{
IItemContainerGenerator generator = ic.ItemContainerGenerator;
// write visuals using a batch operation
VisualsToXpsDocument collator = (VisualsToXpsDocument)xdw.CreateVisualsCollator();
collator.BeginBatchWrite();
if (WritePageRange(collator, generator, range))
collator.EndBatchWrite();
}
private bool WritePageRange(VisualsToXpsDocument collator, IItemContainerGenerator generator, PageRange range)
{
//    Get the generator position of the first data item
//    PageRange reflects user's selection starts from 1
GeneratorPosition startPos = generator.GeneratorPositionFromIndex(range.PageFrom - 1);
//    If PageFrom > PageTo, print in reverse order
//    UPDATE: never occurs; PrintDialog always 'normalises' the PageRange
GeneratorDirection direction = (range.PageFrom <= range.PageTo) ? GeneratorDirection.Forward : GeneratorDirection.Backward;
using (generator.StartAt(startPos, direction, true))
{
for (int numPages = Math.Abs(range.PageTo - range.PageFrom) + 1; numPages > 0; --numPages)
{
bool newlyRealized;
// Get or create the child
UIElement next = generator.GenerateNext(out newlyRealized) as UIElement;
if (newlyRealized)
{
generator.PrepareItemContainer(next);
}
//    The collator doesn't like ContentPresenters and produces blank pages
//    for pages 2-n.  Finding the child of the ContentPresenter and writing
//    that solves seems to solve the problem
if (next is ContentPresenter)
{
ContentPresenter presenter = (ContentPresenter)next;
presenter.UpdateLayout();
presenter.ApplyTemplate();    //    not sure if this is necessary
DependencyObject child = VisualTreeHelper.GetChild(presenter, 0);
if (child is UIElement)
next = (UIElement)child;
}
try
{
collator.Write(next);
}
catch
{
//    if user prints to Microsoft XPS Document Writer
//    and cancels the SaveAs dialog, we get an exception.
return false;
}
}
}
return true;
}

PrintItemsTo()，显示打印对话框以打印到任何打印机，而WriteAllItems显示对话框以另存为PDF。