在 WPF 文档查看器中通知页面更改

Question

我有一个 C# Wpf 项目，我已在其中成功加载了 Xps。文件到文档查看器。我希望能够在我的 C# 代码中包含一个变量，当您滚动文档时该变量会注意到页面更改。 到目前为止，我已经发现，xaml 代码有一个函数，如果您滚动到下一页，它会自动更改页码：

    <DocumentViewer x:Name="viewDocument" HorizontalAlignment="Left" VerticalAlignment="Top" Height="Auto" Grid.Row="0" Grid.Column="0" >
            <FixedDocument></FixedDocument>
        </DocumentViewer>
    <TextBlock Text="{Binding ElementName=viewDocument,Path=MasterPageNumber}" Grid.Row="1"/>

我的最终目标是停止用户在每个页面上花费的时间，这就是为什么我需要能够将当前页码与我的代码中的一个变量连接起来，而这在上面的示例中是无法做到的。我试图实现 INotifyPropertyChanged，但我对 C# 还很陌生，我找不到错误。它将变量设置为第一页，但之后它不会更新。

这是我的视图模型：

using System; using System.ComponentModel; 
namespace Tfidf_PdfOnly {
public class MainViewModel : INotifyPropertyChanged
{

    private int _myLabel;

    public int MyLabel
    {
        get
        {
            return this._myLabel;
        }
        set
        {
            this._myLabel = value;
            NotifyPropertyChanged("MyLabel");
        }
    }


    public MainViewModel()
    {
        _myLabel = 55;
    }

    public event PropertyChangedEventHandler PropertyChanged;
    public void NotifyPropertyChanged(String info)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
    }
}
}

这是在我的 Document_Viewer.xaml.cs 文件中

 XpsDocument document1 = new XpsDocument(path, System.IO.FileAccess.Read);
        //load the file into the viewer
        viewDocument.Document = document1.GetFixedDocumentSequence();

        MainViewModel vm = new MainViewModel();
        this.DataContext = vm;
        vm.MyLabel = viewDocument.MasterPageNumber; 

为了查看它是否有效，我将它绑定到 UI 上的标签：

<DocumentViewer x:Name="viewDocument" HorizontalAlignment="Left" VerticalAlignment="Top" Height="Auto" Grid.Row="0" Grid.Column="0" >
            <FixedDocument></FixedDocument>
        </DocumentViewer>
    <TextBlock Text="{Binding MyLabel, UpdateSourceTrigger=PropertyChanged, NotifyOnSourceUpdated=True}" Grid.Row="1" HorizontalAlignment="Right"/>

我希望我的问题很清楚，任何帮助都值得赞赏！

Answer 1

DocumentViewer 有一个名为 MasterPageNumber 的属性（它应该是文档的页面索引）。以下示例使用 Prism 和 Blend SDK（行为）。转换器又快又脏。对于时间，您可以使用 StopWatch 实例来跟踪页面更改之间的时间间隔。

MVVM 方法

视图模型

public class ShellViewModel : BindableBase
{
    private int _currentPage;

    public string Title => "Sample";

    public string DocumentPath => @"c:\temp\temp.xps";

    public int CurrentPage
    {
        get => _currentPage;
        set => SetProperty(ref _currentPage, value);
    }

    public ICommand PageChangedCommand => new DelegateCommand<int?>(i => CurrentPage = i.GetValueOrDefault());
}

查看

<Window x:Class="Poc.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:viewModels="clr-namespace:Poc.ViewModels"
    xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
    xmlns:behaviors="clr-namespace:Poc.Views.Interactivity.Behaviors"
    xmlns:converters="clr-namespace:Poc.Views.Converters"
    xmlns:controls1="clr-namespace:Poc.Views.Controls"
    mc:Ignorable="d"
    Title="{Binding Title}" Height="350" Width="525">
<Window.Resources>
    <converters:PathToDocumentConverter x:Key="PathToDocumentConverter"></converters:PathToDocumentConverter>
</Window.Resources>
<Window.DataContext>
    <viewModels:ShellViewModel />
</Window.DataContext>
<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="*"></RowDefinition>
        <RowDefinition Height="Auto"></RowDefinition>
    </Grid.RowDefinitions>
    <DocumentViewer Document="{Binding DocumentPath,Converter={StaticResource PathToDocumentConverter}}">
        <i:Interaction.Behaviors>
            <behaviors:DocumentViewerBehavior PageViewChangedCommand="{Binding PageChangedCommand}"></behaviors:DocumentViewerBehavior>
        </i:Interaction.Behaviors>
    </DocumentViewer>
    <TextBlock Grid.Row="1" Text="{Binding CurrentPage}"></TextBlock>
</Grid>

行为

public class DocumentViewerBehavior : Behavior<DocumentViewer>
{
    public static readonly DependencyProperty PageViewChangedCommandProperty = DependencyProperty.Register(nameof(PageViewChangedCommand), typeof(ICommand), typeof(DocumentViewerBehavior));

    public ICommand PageViewChangedCommand
    {
        get => (ICommand)GetValue(PageViewChangedCommandProperty);
        set => SetValue(PageViewChangedCommandProperty, value);
    }

    protected override void OnAttached()
    {
        base.OnAttached();

        AssociatedObject.PageViewsChanged += OnPageViewsChanged;
    }

    private void OnPageViewsChanged(object sender, EventArgs e) => PageViewChangedCommand?.Execute(AssociatedObject.MasterPageNumber);

    protected override void OnDetaching()
    {
        base.OnDetaching();

        AssociatedObject.PageViewsChanged -= OnPageViewsChanged;
    }
}

转换器

public class PathToDocumentConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var fileInfo = new FileInfo((string)value);

        if (fileInfo.Exists)
        {
            if (String.Compare(fileInfo.Extension, ".XPS", StringComparison.OrdinalIgnoreCase) == 0)
            {
                return new XpsDocument(fileInfo.FullName, FileAccess.Read).GetFixedDocumentSequence();
            }
        }

        return value;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}