Question

所以，我有一个wpf表单，它发送到一个站点，解析html，并返回一个强类型的'href'值列表。（是的，这是我自己的网站）

我正在利用backgroundworker来释放UI的挂断，并呈现正在运行的进度条。

虽然它只对网站的第一页有用，但如果我决定递归网站，进度条会挂起，而递归就会发生，那么一旦递归完成，进度条就会恢复生机。

你能告诉我这里做错了什么吗？并且可以指导我使用进度条正确使用所述后台工作程序......基本上，进度条应该在执行任务时运行，但我假设基于代码，这确实不是这种情况。

以下是完成此操作的窗口的代码隐藏：

Imports System.Threading.Tasks
Imports System.Threading

Class MainWindow

Private _previousCursor As Cursor = Mouse.OverrideCursor
Private _Spider As New Spider.SpiderIt
Private _Worker As New ComponentModel.BackgroundWorker
Private _RunCount As Integer = 0

Private Sub MainWindow_Loaded(sender As Object, e As System.Windows.RoutedEventArgs) Handles Me.Loaded
    Me.workProgress.Visibility = Windows.Visibility.Hidden
    _Worker.WorkerReportsProgress = True
    _Worker.WorkerSupportsCancellation = True
    AddHandler _Worker.DoWork, New System.ComponentModel.DoWorkEventHandler(AddressOf Spider)
    AddHandler _Worker.ProgressChanged, New System.ComponentModel.ProgressChangedEventHandler(AddressOf worker_ProgressChanged)
    AddHandler _Worker.RunWorkerCompleted, New System.ComponentModel.RunWorkerCompletedEventHandler(AddressOf worker_RunWorkerCompleted)
    Me.SiteParse.Focus()
End Sub

Private Sub SiteParseKeyDown(sender As System.Object, e As System.Windows.Input.KeyEventArgs)
    If (e.Key = Key.Return) Then
        Me.btnParseAll.IsEnabled = False
        Me.btnParseSelected.IsEnabled = False
        Me.SiteParse.IsEnabled = False
        Mouse.OverrideCursor = Cursors.Wait
        Me.workProgress.Visibility = Windows.Visibility.Visible
        _Worker.RunWorkerAsync(New Typing() With {.Url = SiteParse.Text, .Recurse = Recurse.IsChecked})
    End If
End Sub

Private Sub btnParseAll_Click(sender As Object, e As System.Windows.RoutedEventArgs) Handles btnParseAll.Click
    Me.btnParseAll.IsEnabled = False
    Me.btnParseSelected.IsEnabled = False
    Me.SiteParse.IsEnabled = False
    Dim _TL As New List(Of DGTyping)
    Using New WaitCursor
        For Each Item In DG_SiteLinks.Items
            _TL.Add(New DGTyping() With {
                    .SiteUrl = Item.SiteUrl,
                    .SiteTitle = Item.SiteTitle
                })
        Next
    End Using
    Dim _T As New ParseLinks(Me, _TL)
    _T.ShowDialog()
End Sub

Private Sub btnParseSelected_Click(sender As Object, e As System.Windows.RoutedEventArgs) Handles btnParseSelected.Click
    Me.btnParseAll.IsEnabled = False
    Me.btnParseSelected.IsEnabled = False
    Me.SiteParse.IsEnabled = False
    Dim _TL As New List(Of DGTyping)
    Using New WaitCursor
        For Each Item In DG_SiteLinks.SelectedItems
            _TL.Add(New DGTyping() With {
                    .SiteUrl = Item.SiteUrl,
                    .SiteTitle = Item.SiteTitle
                })
        Next
    End Using
    Dim _T As New ParseLinks(Me, _TL)
    _T.ShowDialog()
End Sub

#Region "Get Site Links"

Private Sub Spider(sender As Object, e As System.ComponentModel.DoWorkEventArgs)
    'Do the work here, but need to get the value of SiteParse first
    With _Spider
        .UrlToParse = DirectCast(e.Argument.Url, String)
        .ShouldRecurse = DirectCast(e.Argument.Recurse, Boolean)
        .RecurseLevels = 20
        .SpiderIt(_Worker)
    End With
End Sub

Private Sub worker_ProgressChanged(sender As Object, e As System.ComponentModel.ProgressChangedEventArgs)
    workProgress.Value = e.ProgressPercentage
End Sub

Private Sub worker_RunWorkerCompleted(sender As Object, e As System.ComponentModel.RunWorkerCompletedEventArgs)
    EndRest()
    Dim _IL As List(Of Spider.Typing.InternalLinks)
    _IL = _Spider.InternalLinks()
    Dim _TL As New List(Of DGTyping)
    For Each item In _IL
        _TL.Add(New DGTyping() With {
                .SiteUrl = item.Url,
                .SiteTitle = If(item.Title.Length > 0, item.Title, item.Content)
            })
    Next
    _IL.Clear()
    Me.DG_SiteLinks.ItemsSource = _TL
    EndSync()
End Sub

Private Sub BrowseSite(sender As Object, e As RoutedEventArgs)
    Dim _URL As String = DirectCast(sender, TextBlock).Text
    Dim _T As New Browser(_URL)
    _T.ShowDialog()
End Sub

Private Sub Window_Closing(sender As Object, e As System.ComponentModel.CancelEventArgs)
    If _Worker IsNot Nothing Then
        If _Worker.IsBusy Then
            _Worker.CancelAsync()
        End If
    End If
End Sub

Private Sub EndSync()
    _Worker.CancelAsync()
    _Worker.Dispose()
    _Spider.Dispose()
End Sub

Private Sub EndRest()
    workProgress.Value = 0
    workProgress.Visibility = Windows.Visibility.Hidden
    Me.btnParseAll.IsEnabled = True
    Me.btnParseSelected.IsEnabled = True
    Me.SiteParse.IsEnabled = True
    Mouse.OverrideCursor = _previousCursor
End Sub

Partial Public Class Typing
    Public Property Url As String
    Public Property Recurse As Boolean
End Class

Partial Public Class DGTyping
    Public Property SiteUrl As String
    Public Property SiteTitle As String
End Class

#End Region

End Class

.SpiderIt（）走出指定的站点，将html抓取为HDocument（SuperstarCoders LinqToHtml），解析内部链接，并将它们抛出到强类型列表中。这是在一个单独的类程序集中完成的，并且表现完美。

SpiderIt方法并包含类：

Imports Superstar.Html.Linq
Imports System.Threading.Tasks

Public Class SpiderIt
Implements IDisposable

#Region "Public Properties"

''' <summary>
''' Specify the initial URL to parse
''' </summary>
''' <value></value>
''' <returns></returns>
''' <remarks></remarks>
Public Property UrlToParse As String

''' <summary>
''' Should this recurse the internal links of the site
''' </summary>
''' <value></value>
''' <returns></returns>
''' <remarks></remarks>
Public Property ShouldRecurse As Boolean = False

''' <summary>
''' Specify the number of levels to recurse
''' </summary>
''' <value></value>
''' <returns></returns>
''' <remarks></remarks>
Public Property RecurseLevels As Long = 0

''' <summary>
''' Returns a message from the SpiderIt method
''' </summary>
''' <value></value>
''' <returns></returns>
''' <remarks></remarks>
Public ReadOnly Property Message() As String
    Get
        Return _Msg
    End Get
End Property

''' <summary>
''' Returns a strongly typed list of internal links
''' </summary>
''' <value></value>
''' <returns></returns>
''' <remarks></remarks>
Public ReadOnly Property InternalLinks() As List(Of Typing.InternalLinks)
    Get
        Return _InternalLinkList
    End Get
End Property

''' <summary>
''' Returns a strongly typed list of external links
''' </summary>
''' <value></value>
''' <returns></returns>
''' <remarks></remarks>
Public ReadOnly Property ExternalLinks() As List(Of Typing.ExternalLinks)
    Get
        Return _ExternalLinkList
    End Get
End Property

#End Region

#Region "Internal Properties"

Private disposedValue As Boolean
Private _Msg As String
Private _Ctr As Long = 0
Private _InternalLinkList As New List(Of Typing.InternalLinks)
Private _ExternalLinkList As New List(Of Typing.ExternalLinks)
Private _DLer As New Downloader
Private _RCt As Long = 0

#End Region

#Region "Public Methods"

''' <summary>
''' Parse with the specified values
''' </summary>
''' <returns>Boolean</returns>
''' <remarks>Returns true or false, based on if it has completed, as well as a message
''' Spits out 2 strongly typed lists.  Both internal and external URLs
''' </remarks>
Public Function SpiderIt(ByVal _Worker) As Boolean
    For i As Integer = 1 To 99
        _Worker.ReportProgress(i)
        System.Threading.Thread.Sleep(50)
    Next
    _Worker.ReportProgress(100)
    Dim _Doc As HDocument = _DLer.DownloadHDoc(UrlToParse)
    With _Doc
        If _Doc Is Nothing Then
            _Msg = "There is no document to parse."
            Return False
        Else
            Try
                Dim _AL = .Descendants("a")
                'Parse the internal links
                ParseLinks(_AL)
                _Msg = "Internal Link List Built"
                Return True
            Catch ex As Exception
                _Msg = ex.Message
                Return False
            End Try
        End If
    End With
End Function

#End Region

#Region "Internal Methods"

#Region "Spider Helpers"

Private Sub ParseLinks(ByVal _AL As IEnumerable(Of HElement))
    Try
        Dim _Link As String, _D As HDocument
        For i As Long = 0 To _AL.Count - 1
            If _AL(i).Attribute("href") IsNot Nothing AndAlso Not (_AL(i).Attribute("href").Value.Contains("//") OrElse
                    _AL(i).Attribute("href").Value.Contains("http://") OrElse
                    _AL(i).Attribute("href").Value.Contains("https://") OrElse
                    _AL(i).Attribute("href").Value.Contains("ftp://") OrElse
                    _AL(i).Attribute("href").Value.Contains("mailto:") OrElse
                    _AL(i).Attribute("href").Value.Contains("#")) Then
                _Link = UrlToParse & "/" & _AL(i).Attribute("href").Value
                If Not (_InternalLinkList.Any(Function(x) x.Url = _Link.Replace("//", "/").Replace("http:/", "http://").Replace("https:/", "https://"))) Then
                    AddInternalLinks(_Link.Replace("//", "/").Replace("http:/", "http://").Replace("https:/", "https://"),
                                     If(_AL(i).Attribute("target") Is Nothing,
                                         String.Empty,
                                         _AL(i).Attribute("target").Value),
                                     _AL(i).Value,
                                     If(_AL(i).Attribute("title") Is Nothing,
                                         String.Empty,
                                         _AL(i).Attribute("title").Value))
                    If ShouldRecurse Then
                        _RCt += 1
                        If _RCt <= RecurseLevels Then
                            _D = _DLer.DownloadHDoc(_Link)
                            ParseLinks(_D.Descendants("a"))
                        End If
                    End If
                End If
            Else
                _Link = _AL(i).Attribute("href").Value
                If Not (_ExternalLinkList.Any(Function(x) x.Url = _Link)) Then
                    AddExternalLinks(_Link,
                                     If(_AL(i).Attribute("target") Is Nothing,
                                         String.Empty,
                                         _AL(i).Attribute("target").Value),
                                     _AL(i).Value,
                                     If(_AL(i).Attribute("title") Is Nothing,
                                         String.Empty,
                                         _AL(i).Attribute("title").Value))
                End If
            End If
        Next
    Catch ex As Exception
        _Msg += ex.StackTrace
    End Try
End Sub

Private Sub AddExternalLinks(ByVal _Link As String, ByVal _Target As String, ByVal _Content As String, ByVal _Title As String)
    Try
        _ExternalLinkList.Add(New Typing.ExternalLinks With {
                            .Url = _Link,
                            .Content = _Content,
                            .Target = _Target,
                            .Title = _Title
                        })
    Catch ex As Exception
        _Msg += ex.StackTrace
    End Try
End Sub

Private Sub AddInternalLinks(ByVal _Link As String, ByVal _Target As String, ByVal _Content As String, ByVal _Title As String)
    Try
        _InternalLinkList.Add(New Typing.InternalLinks With {
                            .Url = _Link,
                            .Content = _Content,
                            .Target = _Target,
                            .Title = _Title
                        })
    Catch ex As Exception
        _Msg += ex.StackTrace
    End Try
End Sub

#End Region

#Region "IDisposable Support"

Protected Overridable Sub Dispose(disposing As Boolean)
    If Not Me.disposedValue Then
        If disposing Then
        End If
        _Msg = String.Empty
        _InternalLinkList.Clear()
        _ExternalLinkList.Clear()
        _DLer.Dispose()
    End If
    Me.disposedValue = True
End Sub

Public Sub Dispose() Implements IDisposable.Dispose
    Dispose(True)
    GC.SuppressFinalize(Me)
End Sub

#End Region

#End Region

End Class

Answer 1

我发布这个作为答案'因为评论文字太长了。

也许我错过了一些东西（以这种格式阅读代码很痛苦）。

您的计数从1到99，并且每50毫秒报告一次进度。在两者之间似乎没有发生任何事情，我的意思是工作负荷会增加一些真正的延迟。然后你报告100％，然后它似乎实际上加载文件和解析，这需要一段时间，我猜。

你不应该在ParseLinks（）方法的某个地方抛出一个ReportProgress（）。当然，您必须能够计算要解析的节点数，这样您才能以一定的速度报告进度，这与工作完成时的100％进度相吻合。

编写另一个递归方法，只提前计算节点数（应该很快），然后使用该数字，你将知道要传递给ReportProgress（）的值（你应该再次调用ParseLinks（））所以你将有稳定的进步，达到100％。（显然你必须将对BackgroundWorker的引用传递给ParseLinks（）to）

可能很难，但没人说这很容易：D。

干杯。

WPF后台工作者和ProgressBar

1 个答案: