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VB.NET UWP/WinRT Examples

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(VB.NET UWP/WinRT) Facebook Download all Photos to Local Files

Demonstrates how to download all of one's Facebook photos to a local filesystem directory. This sample code keeps a local cache to avoid re-downloading the same photos twice. The program can be run again after a time, and it will download only photos that haven't yet been downloaded.

Chilkat Universal Windows Platform (UWP) / WinRT Downloads

Chilkat for the Universal Windows Platform (UWP)

'  This example requires the Chilkat API to have been previously unlocked.
'  See Global Unlock Sample for sample code.

'  This example will use a local disk cache to avoid re-fetching the same
'  photo id after it's been fetched once.
Dim fbCache As New Chilkat.Cache
'  The cache will use 1 level of 256 sub-directories.
fbCache.Level = 1
'  Use a directory path that makes sense on your operating system..
fbCache.AddRoot("C:/fbCache")

'  This example assumes a previously obtained an access token
Dim oauth2 As New Chilkat.OAuth2
oauth2.AccessToken = "FACEBOOK-ACCESS-TOKEN"

Dim rest As New Chilkat.Rest

'  Connect to Facebook.
Dim success As Boolean = Await rest.ConnectAsync("graph.facebook.com",443,True,True)
If (success <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


'  Provide the authentication credentials (i.e. the access key)
rest.SetAuthOAuth2(oauth2)

'  There are two choices:
'  We can choose to download the photos the person is tagged in or has uploaded
'  by setting type to "tagged" or "uploaded".
rest.AddQueryParam("type","uploaded")

'  To download all photos, we begin with an outer loop that iterates over
'  the list of photo nodes in pages.  Each page returned contains a list of
'  photo node ids.  Each photo node id must be retrieved to get the download URL(s)
'  of the actual image.

'  I don't know the max limit for the number of records that can be downloaded at once.
rest.AddQueryParam("limit","100")

'  Get the 1st page of photos ids.
'  See https://developers.facebook.com/docs/graph-api/reference/user/photos/ for more information.
Dim responseJson As String = Await rest.FullRequestNoBodyAsync("GET","/v2.7/me/photos")
If (rest.LastMethodSuccess <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


Dim photoJson As New Chilkat.JsonObject
Dim saPhotoUrls As New Chilkat.StringArray
Dim sbPhotoIdPath As New Chilkat.StringBuilder

Dim json As New Chilkat.JsonObject
json.EmitCompact = False
json.Load(responseJson)

Dim i As Integer
Dim photoId As String
Dim imageUrl As String

'  Get the "after" cursor.
Dim afterCursor As String = json.StringOf("paging.cursors.after")
While json.LastMethodSuccess = True

    Debug.WriteLine("-------------------")
    Debug.WriteLine("afterCursor = " & afterCursor)

    '  For each photo id in this page...
    i = 0
    Dim numItems As Integer = json.SizeOfArray("data")
    While i < numItems
        json.I = i
        photoId = json.StringOf("data[i].id")
        Debug.WriteLine("photoId = " & photoId)

        '  We need to fetch the JSON for this photo.  Check to see if it's in the local disk cache,
        '  and if not, then get it from Facebook.
        Dim photoJsonStr As String = fbCache.FetchText(photoId)
        If (fbCache.LastMethodSuccess = False) Then
            '  It's not locally available, so get it from Facebook..
            sbPhotoIdPath.Clear()
            sbPhotoIdPath.Append("/v2.7/")
            sbPhotoIdPath.Append(photoId)

            rest.ClearAllQueryParams()
            rest.AddQueryParam("fields","id,album,images")

            Debug.WriteLine("Fetching photo node from Facebook...")

            '  This REST request will continue using the existing connection.
            '  If the connection was closed, it will automatically reconnect to send the request.
            photoJsonStr = Await rest.FullRequestNoBodyAsync("GET",sbPhotoIdPath.GetAsString())
            If (rest.LastMethodSuccess <> True) Then
                Debug.WriteLine(rest.LastErrorText)
                Exit Sub
            End If

            '  Add the photo JSON to the local cache.
            fbCache.SaveTextNoExpire(photoId,"",photoJsonStr)
        End If


        '  Parse the photo JSON and add the main photo download URL to saPhotoUrls
        '  There may be multiple URLs in the images array, but the 1st one is the largest and main photo URL.
        '  The others are smaller sizes of the same photo.
        photoJson.Load(photoJsonStr)
        imageUrl = photoJson.StringOf("images[0].source")
        If (photoJson.LastMethodSuccess = True) Then

            '  Actually, we'll add a small JSON document that contains both the image ID and the URL.
            Dim imgUrlJson As New Chilkat.JsonObject
            imgUrlJson.AppendString("id",photoId)
            imgUrlJson.AppendString("url",imageUrl)
            saPhotoUrls.Append(imgUrlJson.Emit())
            Debug.WriteLine("imageUrl = " & imageUrl)
        End If


        i = i + 1
    End While

    '  Prepare for getting the next page of photos ids.
    '  We can continue using the same REST object.
    '  If already connected, we'll continue using the existing connection.
    '  Otherwise, a new connection will automatically be made if needed.
    rest.ClearAllQueryParams()
    rest.AddQueryParam("type","uploaded")
    rest.AddQueryParam("limit","20")
    rest.AddQueryParam("after",afterCursor)

    '  Get the next page of photo ids.
    responseJson = Await rest.FullRequestNoBodyAsync("GET","/v2.7/me/photos")
    If (rest.LastMethodSuccess <> True) Then
        Debug.WriteLine(rest.LastErrorText)
        Exit Sub
    End If


    json.Load(responseJson)
    afterCursor = json.StringOf("paging.cursors.after")
End While

Debug.WriteLine("No more pages of photos.")

'  Now iterate over the photo URLs and download each to a file.
'  We can use Chilkat HTTP.  No Facebook authorization (access token) is required to download
'  the photo once the URL is known.
Dim http As New Chilkat.Http

'  We'll cache the image data so that if run again, we don't re-download the same image again.
Dim numUrls As Integer = saPhotoUrls.Count
i = 0
Dim urlJson As New Chilkat.JsonObject
Dim imageBytes() As Byte
Dim fac As New Chilkat.FileAccess

While i < numUrls
    urlJson.Load(saPhotoUrls.GetString(i))
    photoId = urlJson.StringOf("id")
    imageUrl = urlJson.StringOf("url")

    '  Check the local cache for the image data.
    '  Only download and save if not already cached.
    imageBytes = fbCache.FetchFromCache(imageUrl)
    If (fbCache.LastMethodSuccess = False) Then
        '   This photo needs to be downloaded.

        Dim sbImageUrl As New Chilkat.StringBuilder
        sbImageUrl.Append(imageUrl)

        '  Let's form a filename..
        Dim extension As String = ".jpg"
        If (sbImageUrl.Contains(".gif",False) = True) Then
            extension = ".gif"
        End If

        If (sbImageUrl.Contains(".png",False) = True) Then
            extension = ".png"
        End If

        If (sbImageUrl.Contains(".tiff",False) = True) Then
            extension = ".tiff"
        End If

        If (sbImageUrl.Contains(".bmp",False) = True) Then
            extension = ".bmp"
        End If


        Dim sbLocalFilePath As New Chilkat.StringBuilder
        sbLocalFilePath.Append("C:/Photos/facebook/uploaded/")
        sbLocalFilePath.Append(photoId)
        sbLocalFilePath.Append(extension)

        imageBytes = Await http.QuickGetAsync(imageUrl)
        If (http.LastMethodSuccess <> True) Then
            Debug.WriteLine(http.LastErrorText)
            Exit Sub
        End If


        '  We've downloaded the photo image bytes into memory.
        '  Save it to the cache AND save it to the output file.
        fbCache.SaveToCacheNoExpire(imageUrl,"",imageBytes)
        fac.WriteEntireFile(sbLocalFilePath.GetAsString(),imageBytes)

        Debug.WriteLine("Downloaded to " & sbLocalFilePath.GetAsString())
    End If


    i = i + 1
End While

Debug.WriteLine("Finished downloading all Facebook photos!")

 

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