Development | Starting Out

Copy any file from the desktop to the Pocket PC and vice versa.
Written by Richard Hands  [author's bio]  [read 82109 times]
Edited by Derek

         

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Read Part One

In the first article in this two part series, I discussed how we can copy Access Databases to Pocket Access Databases, and back again, with the help of a few ActiveSync API calls and a little bit of VB6. This article is designed to show how we can copy any sort of file between the PC and the device.

The first thing you will need before we start, is to download the attached sample code. Contained within the sample code file is a file called RemoteCE.tlb

This file is an invaluable freeware Type Library, which I found at http://www.conduits.com/ce/dev/vbrapi.htm that contains pretty much every Remote API Call (RAPI) definition within the Windows CE Remote API. This saved me days of pulling my hair out trying to work out the correct definitions for Function Calls and their custom data types.

This file is purely to assist developers, it does not need to be distributed with your projects.

Create a new Visual Basic 6 project. Go to the Projects, References option, and click browse. Locate the RemoteCE.tlb file and add it. You now have a whole series of extra functions and user defined types available to you. for those of you familiar with VB, press F2 to open the object browser, select RemoteCETypeLibrary from the top left drop down, and you will be presented with all the definitions. most of the function calls are held within the CERAPI class.

Close the object browser once you are done giving yourself a headache at what you would have otherwise had to figure out on your own, and create a new form in the VB project.

Create two new text fields on the form, called txtDesktopFile and txtPPCFile, and place labels next to them reading 'Desktop File' and 'Pocket PC file' respectively.

Place two command buttons on the form labelling them 'Download' and 'Upload'.

Within the Click event for the Download button, place the following code:

'==================================================

On Error Goto ErrHandler

If CopyFileToPocketPC = False Then
msgbox "An error occurred transferring the file"
Else
msgbox "File copied successfully."
End If

Exit Sub

ErrHandler:
MsgBox Err.Number & " " & Err.Description, _
vbOKOnly + vbCritical

'==================================================

And within the Click Event for the Upload button, place the following code:

'==================================================

On Error Goto ErrHandler

If CopyFileFromPocketPC = False Then
msgbox "An error occurred transferring the file"
Else
msgbox "File copied successfully."
End If

Exit Sub

ErrHandler:
MsgBox Err.Number & " " & Err.Description, _
vbOKOnly + vbCritical

'==================================================

Within the Form_Load event place the following code:

'==================================================

dim intRetVal as integer

intRetVal = CeRapiInit()

If intRetVal <> INIT_SUCCESS Then
MsgBox "Failed to initialise RAPI with device with error " & _
CeGetLastError
CeRapiUninit
End
End If

'==================================================

and within the Form_Unload event place the following code:

'==================================================

CeRapiUninit

'==================================================

These two events ensure that when you start the program, an initialisation call is made to the device, and when you end the program the api is shutdown properly.

These calls could just as easily be placed inside the following functions (and probably should be, to make for a more stable application!)

Now, create a new module in your project called modGeneralFunctions

Within this module, create the following Constants:

Public Const INVALID_HANDLE = -1
Public Const GENERIC_READ = &H80000000
Public Const GENERIC_WRITE = &H40000000 '(1073741824)
Public Const FILE_SHARE_READ = 1
Public Const FILE_SHARE_WRITE = 2
Public Const CREATE_ALWAYS = 2
Public Const OPEN_EXISTING = 3
Public Const INIT_SUCCESS = 0
Public Const WRITE_ERROR = 0
Public Const READ_ERROR = 0

and add these three functions to your form's code window as follows:

'==================================================

Public Function CopyFileToPocketPC() As Boolean

Dim bytBuffer(16384) As Byte
Dim lngFileHandle As Long
Dim lngDestinationHandle As Long
Dim lngNumBytesWritten As Long
Dim filename As String
Dim typFindFileData As CE_FIND_DATA
Dim lngFileSize As Long

'On Error GoTo ErrHandler

'locate the file, and see if it already exists on the device
lngFileHandle = CeFindFirstFile(Form1.txtPPCFile.Text, typFindFileData)

'if we get -1 then the file wasn't found so we can go ahead and create it
'otherwise we dont want to overwrite in this demo, so we will cancel the operation.

If lngFileHandle <> INVALID_HANDLE Then
MsgBox txtPPCFile & " already exists. Operation Cancelled."
CeFindClose lngFileHandle
CopyFileToPocketPC = False
End If

'create the file on the device, and return the handle to the file
filename = Form1.txtPPCFile.Text
lngDestinationHandle = CeCreateFile(filename, GENERIC_WRITE, FILE_SHARE_READ, vbNullString, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, 0)

'if something went wrong in CeCreateFile we will get -1, and therefore need to abort
If lngDestinationHandle = INVALID_HANDLE Then
MsgBox "CeCreateFile Error " & CeGetLastError & " occurred.", vbCritical & vbOKOnly
CopyFileToPocketPC = False
Exit Function
End If

'Call function to read file on the desktop into the byte buffer
If ReadFileAsBinary(Form1.txtDesktopFile.Text, lngFileSize, bytBuffer()) = True Then

'Write contents of Binary buffer to CE file.
'Return value of 0 = failure, non zero = success
intRetVal = CeWriteFile(lngDestinationHandle, bytBuffer(0), lngFileSize, lngNumBytesWritten, 0)

If intRetVal = WRITE_ERROR Then
GoTo ErrHandler
End If

End If

CeCloseHandle lngDestinationHandle

CopyFileToPocketPC = True

Exit Function

ErrHandler:

MsgBox "Error " & CeGetLastError & " Occurred When Copying File " & _
Form1.txtDesktopFile.Text & " To The Device as " & Form1.txtPPCFile.Text, vbCritical & vbOKOnly

If lngDestinationHandle Or lngDestinationHandle <> INVALID_HANDLE Then
CeCloseHandle lngDestinationHandle
End If
CopyFileToPocketPC = False

End Function

'==================================================

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