Question

我正在尝试使用BackgroundWorker实现进度条。

但是进度条会在一秒钟之后隐藏起来并且它不会保持在最顶层。不确定原因。

以下是我的表格代码：

Private Sub btnProgressBarPOC_Click(sender As Object, e As EventArgs) Handles btnProgressBarPOC.Click
    BackgroundWorker = New BackgroundWorker()
    BackgroundWorker.WorkerReportsProgress = True
    autoResetEvent = New AutoResetEvent(False)
    ProgressBar = New frmProgressBar(BackgroundWorker)
    ProgressBar.ShowDialog()

    autoResetEvent.WaitOne()
    MsgBox("Main Done", vbInformation)
End Sub

Sub Processing() Handles BackgroundWorker.DoWork
    BackgroundWorker.ReportProgress(33)
    Threading.Thread.Sleep(5000)

    BackgroundWorker.ReportProgress(66)
    Threading.Thread.Sleep(5000)

    BackgroundWorker.ReportProgress(100)

    MsgBox("Background Done", vbInformation)
    AutoResetEvent.Set()
End Sub

以下是我的代码，其中包含进度条：

Imports System.ComponentModel

Public Class frmProgressBar

    Private WithEvents _BGW As System.ComponentModel.BackgroundWorker
    Private _TaskInProgress As String

    Public WriteOnly Property TaskInProgress()
        Set(value)
            _TaskInProgress = value
            _BGW.ReportProgress(1)
        End Set
    End Property

    Public Sub New(ByVal BGW As System.ComponentModel.BackgroundWorker)
        _BGW = BGW
        InitializeComponent()
    End Sub

    Private Sub frmProgress_Shown(sender As Object, e As System.EventArgs) Handles Me.Shown
        If Not IsNothing(_BGW) Then
            _BGW.RunWorkerAsync()
        End If
    End Sub

    Private Sub _BGW_ProgressChanged(sender As Object, e As System.ComponentModel.ProgressChangedEventArgs) Handles _BGW.ProgressChanged
        progressBar.Value = e.ProgressPercentage

        If Me.Text <> _TaskInProgress Then
            Me.Text = _TaskInProgress
        End If
    End Sub

    Private Sub _BGW_RunWorkerCompleted(sender As Object, e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles _BGW.RunWorkerCompleted
        Me.Close()
        _TaskInProgress = ""
    End Sub

    'Private Sub _BGW_DoWork(sender As Object, e As DoWorkEventArgs) Handles _BGW.DoWork
    '    Do While True
    '        ' Has the background worker be told to stop?
    '        If _BGW.CancellationPending Then
    '            ' Set Cancel to True
    '            e.Cancel = True
    '            Exit Do
    '        End If
    '        System.Threading.Thread.Sleep(2000) ' Sleep for 1 Second
    '    Loop
    'End Sub
End Class

我在这里上传了我的项目： https://drive.google.com/file/d/0B7gzonuQsNbvaDZvR3ltSl9WNTg/view?usp=sharing

Answer 1

您不需要AutoReset事件，因为您可以处理RunWorkerCompleted事件。目前您正在阻止UI线程。

从RunWorkerAsync中删除msgbox，这应该在你的ui线程上处理。

我怀疑它是导致RunWorkerAsync退出的异常，因此请检查RunWorkerCompleted事件中的错误代码。这可能是由您的TaskInProgress属性引起的，该属性通过环形交叉方式与文本框进行交互，尽管它位于后台线程上。

而是更新TaskInProgress文本框，将其作为ReportProgress的额外参数发送，并从进度框中取回。

BackgroundWorker.ReportProgress(33, "Hello")

Private Sub _BGW_ProgressChanged(sender As Object, e As System.ComponentModel.ProgressChangedEventArgs) Handles _BGW.ProgressChanged
    Me.Text = CStr(e.UserState)
     ....

Answer 2

以下是经过纠正的代码：

Public Class frmMisc
    Private WithEvents BackgroundWorker As BackgroundWorker, ProgressBar As frmProgressBar

    Private Sub btnProgressBarPOC_Click(sender As Object, e As EventArgs) Handles btnProgressBarPOC.Click
        Call RunProcessing()

        MsgBox("Main Done", vbInformation)
    End Sub

    Sub RunProcessing()
        BackgroundWorker = New BackgroundWorker()
        BackgroundWorker.WorkerReportsProgress = True
        ProgressBar = New frmProgressBar(BackgroundWorker)
        ProgressBar.ShowDialog()
    End Sub

    Sub Processing() Handles BackgroundWorker.DoWork
        BackgroundWorker.ReportProgress(33, "Step-1")
        Threading.Thread.Sleep(3000)

        BackgroundWorker.ReportProgress(66, "Step-2")
        Threading.Thread.Sleep(2000)

        BackgroundWorker.ReportProgress(100, "Step-3")
    End Sub
End Class

Public Class frmProgressBar

    Private WithEvents _BGW As System.ComponentModel.BackgroundWorker
    Private _TaskInProgress As String

    Public Sub New(ByVal BGW As System.ComponentModel.BackgroundWorker)
        _BGW = BGW
        InitializeComponent()
    End Sub

    Private Sub frmProgress_Shown(sender As Object, e As System.EventArgs) Handles Me.Shown
        If Not IsNothing(_BGW) Then
            _BGW.RunWorkerAsync()
        End If
    End Sub

    Private Sub _BGW_ProgressChanged(sender As Object, e As System.ComponentModel.ProgressChangedEventArgs) Handles _BGW.ProgressChanged
        progressBar.Value = e.ProgressPercentage

        Me.Text = e.UserState
    End Sub

    Private Sub _BGW_RunWorkerCompleted(sender As Object, e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles _BGW.RunWorkerCompleted
        Me.Close()
        _TaskInProgress = ""
    End Sub
End Class

我在ProgressChanged之外做了Me.Text甚至是造成这个问题。感谢@Hans提供关于此的提示！

VB.net - 使用BackgroundWorker的Progressbar

2 个答案: