Cancel Queued Download

[Ohanian]

I have a b4a project that contains 2 activities, Main and Download, that main activity contains a button that calls the second activity, the 2nd activity has 3 imageviews , here's the code :

Sub Globals
   'These global variables will be redeclared each time the activity is created.
   'These variables can only be accessed from this module.
   Dim imgDownload1, imgDownload2, imgDownload3 As ImageView
   Dim ImageJob As HttpJob
End Sub

Sub Activity_Create(FirstTime As Boolean)
   ImageJob.ContentType = ""
   ImageJob.Initialize("GetImage", Me)

   imgDownload1.Initialize("")
   Activity.AddView(imgDownload1,0,0, 100dip, 100dip)
   imgDownload1.Gravity = Gravity.FILL
   imgDownload2.Initialize("")
   Activity.AddView(imgDownload2,0,100dip, 100dip, 100dip)
   imgDownload2.Gravity = Gravity.FILL
   imgDownload3.Initialize("")
   Activity.AddView(imgDownload3,0,200dip, 100dip, 100dip)
   imgDownload3.Gravity = Gravity.FILL
   
   ProgressDialogShow("Please Wait...")
   
   Dim i As Int
   For i = 1 To 3
      Dim ImageJob As HttpJob
      ImageJob.ContentType = ""
      ImageJob.Initialize("GetMainImage", Me)
      Dim strFileName As String
      ImageJob.ExtraData1 = i
      Select Case ImageJob.ExtraData1
         Case "1"
               ImageJob.Download2("http://fronttowardsgamer.com/wp-content/uploads/2011/12/microsoft-logo.jpg", Array As String("id", 1))
         Case "2"
               ImageJob.Download2("http://blog.tmcnet.com/blog/rich-tehrani/uploads/old-microsoft-logo.jpg", Array As String("id", 1))
         Case "3"
               ImageJob.Download2("http://blog.tmcnet.com/blog/rich-tehrani/uploads/old-microsoft-logo.jpg", Array As String("id", 1))                     
      End Select
   Next
End Sub

Sub JobDone (Job As HttpJob)
   If Job.Success = True Then
      Select Job.JobName            
            
         Case "GetMainImage"
            Try
               Select Case Job.ExtraData1
                  Case "1"
                        imgDownload1.Bitmap = Job.GetBitmap
                  Case "2"
                        imgDownload2.Bitmap = Job.GetBitmap
                  Case "3"
                     imgDownload3.Bitmap = Job.GetBitmap                  
                     ProgressDialogHide
               End Select
            Catch
               ToastMessageShow("Error 1: " & Job.ErrorMessage & CRLF &  LastException.Message, True)
            End Try            
            
      End Select
      Job.Release
   End If   
End Sub

With a high speed internet connection there's no problem, but when we have a middle or low speed connection, when the image download is in progress, because it takes a while to get the image, if the user push the back button the app returns to Main activity but suddenly it jump to Download activity until the download is finished.
I want to know is there any way to cancel the download process in this scenario?

Tanx in advance

 

[Erel]

You can abort the download by closing HttpClient. However in most cases it is better to use a service to handle the responses. You can then decide what to do with the image.

 

[Ohanian]

Thank you Erel, can you be more specific how can I close the HttpClient in this scenario?

 

[Erel]

Add this code to Service_Destory:

Sub Service_Destroy
   Dim r As Reflector
   r.Target = hc
   r.Target = r.GetField("client")
   r.Target = r.RunMethod("getConnectionManager")
   r.RunMethod("shutdown")
End Sub

This should kill all currently running tasks when you call StopService(HttpUtils2Service).