进度条问题。在读取数据库时让 UI 线程更新

Question

我无法更新进度条。只要有一个移动的选框栏，我就可以了。基本上，我正在阅读 SqliteReader.vb 类中的数据库例程。我是 Visual Basic 的新手，我确定我需要使用 worker_DoWork 例程，但我不确定如何将来自 Form1: graphData、graphComputations、m_debug 的变量公开给 worker_DoWork 子程序。这通常是怎么做的？

Public Class SqliteReader
   Public Sub ReadDataBase
     End Sub
End Class

这是更新主窗体 Form1.vb 上的图形（zedgraph 元素）。我像这样从主窗体调用进度条：

    ProgressBar.Initialize(channelArray, computationArray, m_debug)        

ProgressBar.vb 下面：

Partial Public Class ProgressBar
    Dim DataAcquisition As New SqliteReader
    Dim WithEvents worker As New BackgroundWorker

Public Sub Initialize(ByRef graphData As Channels(), ByRef graphComputations As Computations(), ByVal m_debug As Integer)
    DataAcquisition = SqliteReader.GetInstance()
    Me.Show()
    Me.Update()
    Dim Update_Thread As Thread(AddressOf Update_ThreadExecute)

    Update_Thread.Priority = ThreadPriority.Normal
    Update_Thread.Start()
    DataAcquisition.ParseEntireDatabase(graphData, graphComputations, m_debug)
    Me.Close()
End Sub


Private Sub ProgressBarStart(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
      DataAcquisition = SqliteReader.GetInstance()
      progress.Style = ProgressBarStyle.Marquee
      worker.WorkerReportsProgress = True
      worker.WorkerSupportsCancellation = True
      worker.RunWorkerAsync()
  End Sub

  Private Sub worker_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles worker.DoWork
         Dim worker As BackgroundWorker = DirectCast(sender, BackgroundWorker)
         DataAcquisition = SqliteReader.GetInstance()
         ' I probably need 
         ' DataAcquisition.ParseEntireDatabase(graphData, graphComputations, m_debug)
         ' here... but how do I expose graphdata, graphcomputations and m_debug to this sub?
         End Sub

  Private Sub worker_ProgressChanged(ByVal sender As Object, ByVal e As System.ComponentModel.ProgressChangedEventArgs) Handles worker.ProgressChanged
      dataProgress = CInt(((DataAcquisition.currentRow + 1) / DataAcquisition.totalRows) * 100)
      progress.Value = dataProgress
  End Sub

Answer 1

RunWorkerAsync has a second version that takes a parameter.您可以使用它来传递您的工作人员需要的任何值（或引用）。

也就是说，您不应该从工作人员内部更新表单元素。当您希望 UI 更新时，您的工作人员应该触发 ProgressChanged 事件，并在那里处理它。 That one also has a version that can send a value back.（如果您发回数组、列表或自定义类，则可以返回许多值。）

最后一步是您需要实际触发 ProgressChanged。 DataAcquisition.ParseEntireDatabase 可能不会这样做，在这种情况下，使用它不会允许此方法起作用。

Answer 2

如果graphData, graphComputations, m_debug 已经是ProgressBar 的成员，而worker_DoWork 是ProgressBar 的成员，那么您无需再做任何事情。您应该可以直接访问它们。

Answer 3

对于上面的 Rapunzo.. 我的最终解决方案是这样的：

Partial Public Class ProgressBar
Dim _mDataAcquisition As New SqliteReader
Public Property DataProgress As Integer = 0
Dim WithEvents _mProgressWorker As New BackgroundWorker
Public Sub Initialize(ByRef graphData As List(Of Channels), ByRef auxData As List(Of Channels), _
                      ByRef graphComputations As List(Of Computations))
    _mDataAcquisition = SqliteReader.GetInstance()
    Show()
    Update()
    _mDataAcquisition.ParseEntireDatabase(graphData, auxData, graphComputations)
    Close()
End Sub
Private Sub ProgressBarStart(ByVal sender As System.Object, ByVal e As EventArgs) Handles MyBase.Load
    progress.Style = ProgressBarStyle.Blocks
    _mProgressWorker.WorkerReportsProgress = True
    _mProgressWorker.WorkerSupportsCancellation = True
    _mProgressWorker.RunWorkerAsync()
    progress.Visible = True
    progress.Maximum = 100
    progress.Value = 0
End Sub
Public Sub WorkerProgressChanged()
    progress.Value = DataProgress
    Invalidate()
End Sub
Private Sub WorkerRunWorkerCompleted(ByVal sender As Object, _
                                     ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) _
                                     Handles _mProgressWorker.RunWorkerCompleted
    progress.Visible = False
    progress.Value = 0
    Close()
End Sub

从那里，只需调用 ProgressBar.Initialize 即可启动它

更新：

    ProgressBar.DataProgress = CInt((currentIt / totalIt) * 100)
    ProgressBar.WorkerProgressChanged()

结束：

    ProgressBar.DataProgress = 100
    ProgressBar.WorkerProgressChanged()

希望这会有所帮助。