Android Question how to zoom in and out image in the layout

#Region  Project Attributes
    #ApplicationLabel: B4A Example
    #VersionCode: 1
    #VersionName:
    'SupportedOrientations possible values: unspecified, landscape or portrait.
    #SupportedOrientations: unspecified
    #CanInstallToExternalStorage: False
#End Region

#Region  Activity Attributes
    #FullScreen: False
    #IncludeTitle: True
#End Region

Sub Process_Globals
    'These global variables will be declared once when the application starts.
    'These variables can be accessed from all modules.

End Sub

Sub Globals
    'Dim ImageView3 As ImageView
    'Dim ImageView2 As ImageView
    Dim ImageView1 As ImageView
    'Dim ImageView4 As ImageView
End Sub

Sub Activity_Create(FirstTime As Boolean)
    Activity.LoadLayout("1")
    'ImageView1.
End Sub

Sub Activity_Resume
    Dim links As Map
    links.Initialize
    links.Put(ImageView1, "http://kccug.com/KabojjaApp/work/P1.png")
    'links.Put(ImageView2, "http://www.b4x.com/basic4android/images/SS-2013-03-04_11.42.38.png")
    'links.Put(ImageView3, "http://www.b4x.com/basic4android/images/SS-2013-03-04_11.52.19.png")
    'links.Put(ImageView4, "http://www.b4x.com/basic4android/images/SS-2012-02-06_12.45.56.png")
    CallSubDelayed2(ImageDownloader, "Download", links)
End Sub

Sub Activity_Pause (UserClosed As Boolean)
    CallSub(ImageDownloader, "ActivityIsPaused")
End Sub

#Region  Service Attributes
    #StartAtBoot: False
#End Region

Sub Process_Globals
    Private cache As Map
    Private tasks As Map
    Private ongoingTasks As Map
End Sub

Sub Service_Create
    tasks.Initialize
    cache.Initialize
    ongoingTasks.Initialize
End Sub

Sub Service_Start (StartingIntent As Intent)

End Sub

Sub Service_Destroy

End Sub

Sub Download (ImageViewsMap As Map)
    For i = 0 To ImageViewsMap.Size - 1
        tasks.Put(ImageViewsMap.GetKeyAt(i), ImageViewsMap.GetValueAt(i))
        Dim link As String = ImageViewsMap.GetValueAt(i)
        If cache.ContainsKey(link) Then
            Dim iv As ImageView = ImageViewsMap.GetKeyAt(i)
            iv.SetBackgroundImage(cache.Get(link))
         
        Else If ongoingTasks.ContainsKey(link) = False Then
            ongoingTasks.Put(link, "")
            Dim j As HttpJob
            j.Initialize(link, Me)
            j.Download(link)
        End If
    Next
End Sub

Sub JobDone(Job As HttpJob)
    ongoingTasks.Remove(Job.JobName)
    If Job.Success Then
        Dim bmp As Bitmap = Job.GetBitmap
        cache.Put(Job.JobName, bmp)
        If tasks.IsInitialized Then
            For i = 0 To tasks.Size - 1
                Dim link As String = tasks.GetValueAt(i)
                If link = Job.JobName Then
                    Dim iv As ImageView = tasks.GetKeyAt(i)
                    iv.SetBackgroundImage(bmp)
                End If
            Next
        End If
    Else
        Log("Error downloading image: " & Job.JobName & CRLF & Job.ErrorMessage)
    End If
    Job.Release
End Sub
Sub ActivityIsPaused
    tasks.Clear
End Sub