Android Question Document path not valid when viewing pdf

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
    'These global variables will be redeclared each time the activity is created.
    'These variables can only be accessed from this module.

    Private btnSearch As Button
    Private btnView As Button
    Private testview As String
End Sub

Sub Activity_Create(FirstTime As Boolean)
    'Do not forget to load the layout file created with the visual designer. For example:
    Activity.LoadLayout("Main")
   
    'create the directory
    File.MakeDir(File.DirRootExternal, "TestPDF")
   
    'copy the file
    If File.Exists(File.DirRootExternal & "/TestPDF", "Invoice# 57235.pdf") = False Then
        File.Copy(File.DirAssets, "Invoice# 57235.pdf", File.DirRootExternal & "/TestPDF", "Invoice# 57235.pdf")
    End If

End Sub

Sub Activity_Resume

End Sub

Sub Activity_Pause (UserClosed As Boolean)

End Sub



Sub btnSearch_Click
   
    testview = ""
   
    Dim filefrom As FileDialog
        filefrom.FilePath=File.DirRootExternal & "/TestPDF"
          filefrom.Show("List Of Files", "", "OK", "", Null)
          testview = filefrom.ChosenName
 
End Sub
Sub btnView_Click
   
   
    Dim Intent1 As Intent   
    Intent1.Initialize(Intent1.ACTION_VIEW, "file://" & File.Combine(File.DirRootExternal & "/TestPDF/", testview))
    Intent1.SetComponent("android/com.android.internal.app.ResolverActivity")
    Intent1.SetType("application/pdf")

    StartActivity(Intent1)
   
End Sub