Backgroundworker con Pausa

Al classico Backgroundworker si può facilmente aggiungere la funzionalità di Pausa.

Basta creare una semplice classe custom del tipo seguente:

   1:     ''' <summary>

   2:     ''' Classe ereditata da BackgroundWorker per la

   3:     ''' gestione della pausa

   4:     ''' </summary>

   5:     Class BackgroundWorkerWithPause

   6:        Inherits System.ComponentModel.BackgroundWorker

7:

   8:        ''' <summary>

   9:        ''' Flag per mettere in pausa il Worker

  10:        ''' </summary>

  11:        Public IsInPause As Boolean = False

12:

  13:     End Class

Il suo utilizzo è banale. Ad esempio si può creare una form come questa:

Ed inserire il seguente codice:

   1:  Public Class Form1

2:

   3:     Private worker As BackgroundWorkerWithPause = Nothing

   4:     Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonStart.Click

   5:        worker = New BackgroundWorkerWithPause

   6:        worker.WorkerReportsProgress = True

   7:        worker.WorkerSupportsCancellation = True

   8:        AddHandler worker.ProgressChanged, AddressOf Avanzamento

   9:        AddHandler worker.DoWork, AddressOf Esecuzione

  10:        AddHandler worker.RunWorkerCompleted, AddressOf Completamento

  11:        worker.RunWorkerAsync()

  12:     End Sub

13:

  14:     Private Sub ButtonPause_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonPausa.Click

  15:        ' Mette il worker in pausa

  16:        worker.IsInPause = True

  17:     End Sub

18:

  19:     Private Sub ButtonResume_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonResume.Click

  20:        ' Riavvia il worker

  21:        worker.IsInPause = False

  22:     End Sub

23:

  24:     Sub Esecuzione(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs)

  25:        ' Recupera il worker

  26:        Dim worker As BackgroundWorkerWithPause = CType(sender, BackgroundWorkerWithPause)

  27:        ' Esegue un conteggio

  28:        For i As Integer = 1 To 100

  29:           ' Si ferma per un secondo

  30:           System.Threading.Thread.Sleep(1000)

  31:           ' Lancia un progresschanged

  32:           worker.ReportProgress(i)

  33:           ' Verifica se è in pausa

  34:           Do While worker.IsInPause

  35:              ' Si ferma per un secondo

  36:              System.Threading.Thread.Sleep(1000)

  37:              ' Lancia un progresschanged con indicazione della pausa in corso

  38:              worker.ReportProgress(i, "in pausa")

  39:           Loop

  40:        Next

  41:        e.Result = "Worker completato"

  42:     End Sub

43:

  44:     Sub Avanzamento(ByVal sender As Object, ByVal e As System.ComponentModel.ProgressChangedEventArgs)

  45:        Me.Label1.Text = e.ProgressPercentage.ToString & "% "

  46:        If Not e.UserState Is Nothing Then

  47:           Me.Label1.Text &= e.UserState.ToString

  48:        End If

  49:     End Sub

50:

  51:     Sub Completamento(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs)

  52:        Me.Label1.Text = "Terminato"

  53:     End Sub

54:

  55:  End Class

Print | posted on giovedì 25 ottobre 2007 07:15 | Filed Under [ Tips .Net ]

Francesco Geri