Change Snapped Image FILENAME

Sub Globals
    Dim yearstr,monthstr,daystr,hourstr,minstr,secstr As String
    Dim datestr,timestr As String
    Dim str As String
    Dim seperator As String
    Dim path1,root As String
    Dim lastnum,date_time_tick As Long
    Dim picturelist,picturelist2 As List
    Dim picturenum As Int
    Dim checkbtn As Button
    Dim newpic As Boolean
End Sub

Sub Activity_Create(FirstTime As Boolean)
    checkbtn.Initialize("checkbtn")
    Activity.AddView(checkbtn,30%x,30%y,40%x,20%y)
    checkbtn.Text="Check Picture"
    picturelist.Initialize
    picturelist2.Initialize
    root=File.DirRootExternal
    path1 = root & "/DCIM/Camera"
    get_picture_list
    lastnum=0
    For n = 0 To picturelist.Size-1
        str = picturelist.Get(n)
        yearstr=str.SubString2(4,8)
        monthstr=str.SubString2(8,10)
        daystr=str.SubString2(10,12)
        hourstr=str.SubString2(13,15)
        minstr=str.SubString2(15,17)
        secstr=str.SubString2(17,19)
        'Log(yearstr&"   "&monthstr&"  "&daystr&"  "&hourstr&"   "&minstr&"  "&secstr)
        datestr=monthstr&"/"&daystr&"/"&yearstr
        timestr=hourstr&":"&minstr&":"&secstr
        date_time_tick=DateTime.DateTimeParse(datestr,timestr)
        If date_time_tick>lastnum Then
            lastnum=date_time_tick
            picturenum=n
        End If
    Next
End Sub


Sub get_picture_list
    Dim filelist As List
    filelist.Initialize
    filelist = File.ListFiles(path1)
    Dim file1,file2 As String
    picturelist.Clear
    For n = 0 To filelist.Size-1
        file1 = filelist.Get(n)
        file2=file1.ToUpperCase
        If (file2.EndsWith(".PNG")) Or (file2.EndsWith(".BMP")) Or (file2.EndsWith(".JPG")) Or (file2.EndsWith(".JPEG")) Then
            picturelist.Add(file1)
        End If
    Next
End Sub
  
Sub checkbtn_Click
    check_new_picture
End Sub
  
Sub check_new_picture
    Dim filelist As List
    filelist.Initialize
    filelist = File.ListFiles(path1)
    Dim file1,file2,lastpicture As String
    picturelist2.Clear
    For n = 0 To filelist.Size-1
        file1 = filelist.Get(n)
        file2=file1.ToUpperCase
        If (file2.EndsWith(".PNG")) Or (file2.EndsWith(".BMP")) Or (file2.EndsWith(".JPG")) Or (file2.EndsWith(".JPEG")) Then
            picturelist2.Add(file1)
        End If
    Next
  
    For n = 0 To picturelist2.Size-1
        str = picturelist2.Get(n)
        yearstr=str.SubString2(4,8)
        monthstr=str.SubString2(8,10)
        daystr=str.SubString2(10,12)
        hourstr=str.SubString2(13,15)
        minstr=str.SubString2(15,17)
        secstr=str.SubString2(17,19)
        'Log(yearstr&"   "&monthstr&"  "&daystr&"  "&hourstr&"   "&minstr&"  "&secstr)
        datestr=monthstr&seperator&daystr&seperator&yearstr
        timestr=hourstr&":"&minstr&":"&secstr
        'Log(datestr&"    "&timestr)
        date_time_tick=DateTime.DateTimeParse(datestr,timestr)
        'Log(date_time_tick)
        If date_time_tick>lastnum Then
            lastnum=date_time_tick
            picturenum=n
        End If
    Next
    lastpicture=picturelist2.Get(picturenum)
    newpic=True
    For n=0 To picturelist.Size-1
        If lastpicture=picturelist.Get(n) Then
            newpic=False
        End If
    Next
    If newpic Then
        Log("Last picture = "&lastpicture)
        renamefile(lastpicture,"test.jpg")
    End If
End Sub

Sub renamefile(oldfile As String,newfile As String)
    File.Copy(path1,oldfile,path1,newfile)
    File.Delete(path1,oldfile)
End Sub