How to Get Images From Server using App Tethering - delphi

Question

I've 2 Apps Let's call Server And Client.
I'm using Delphi-xe8. App ->Multi-Device Application
In Both Side using: App tethering[tManager,tAProfile], SQLite Database.
In Server SQLite Database I've 6 images. I would like to View that images In Client Side.
In Client Side I've 6 [TImage].
When I Click Button 'Get Image List' I'm getting 6 images with the same view.
I would like 6 images view differently.->[Get From Server Database]
Client "Get Image List" button Code:
procedure TForm1.GetImgLstClick(Sender: TObject);
begin
tAProfile.SendString(tManager.RemoteProfiles.First,'GetImages','');
end;
Server Received Code:
procedure TForm2.tAProfileResourceReceived(const Sender: TObject;
const AResource: TRemoteResource);
var
MS1:TMemorystream;
begin
if AResource.Hint='GetImages' then
begin
MS1:=TMemorystream.Create;
rQuery.Close;
rQuery.SQL.Clear;
rQuery.SQL.Add('select image from users');
rQuery.Open;
while not rQuery.Eof do
begin
tblobField(rQuery.FieldByName('image')).SaveToStream(MS1);
Image1.Bitmap:=nil;
rQuery.Next;
end;
tAProfile.SendStream(tManager.RemoteProfiles.First,'SendImages',MS1);
end;
end;
Client Received Code:
procedure TForm1.tAProfileResourceReceived(const Sender: TObject;
const AResource: TRemoteResource);
var
MS:TMemoryStream;
begin
if AResource.Hint='SendImages' then
begin
Image1.Bitmap.LoadFromStream(AResource.Value.AsStream);
Image2.Bitmap.LoadFromStream(AResource.Value.AsStream);
Image3.Bitmap.LoadFromStream(AResource.Value.AsStream);
Image4.Bitmap.LoadFromStream(AResource.Value.AsStream);
Image5.Bitmap.LoadFromStream(AResource.Value.AsStream);
Image6.Bitmap.LoadFromStream(AResource.Value.AsStream);
end;
end;

Answer 1

Update: I gather from your most recent comment that you want to send your
images one-by-one.
A problem is that a Delphi dataset's TGraphicField supports a number of formats
which may be of variable size, so if you just write them to the server's outbound
stream, there is no way for the client to know, when reading the stream, where the
data of one image ends and the next one begins. A simple solution to that is to have
the server write the size of the image to the stream before it writes the image's
data to the stream, and get the client's code to read the image size so that it
knows how much of what follows is the image's data.
I'm going back to the answer I posted to your other q (Delphi: How to Get All Images From Server Database by using App tethering?), which uses TClientDataSets,
but adapting it so that it sends only the images (and their sizes) in the stream. The
code is still quite simple and should be no different in principle than using FireDAC datasets and a Sqlite data table:
Server
procedure TApp1Form.SendImageStream;
var
StreamToSend,
ImageStream : TMemoryStream;
StreamedImageSize : Integer;
begin
StreamToSend := TMemoryStream.Create;
ImageStream := TMemoryStream.Create;
try
CDS1.DisableControls;
CDS1.First;
while not CDS1.Eof do begin
ImageStream.Clear;
CDS1Graphic.SaveToStream(ImageStream);
ImageStream.Position := 0;
StreamedImageSize := ImageStream.Size;
StreamToSend.Write(StreamedImageSize, SizeOf(Integer));
StreamToSend.CopyFrom(ImageStream, StreamedImageSize);
CDS1.Next;
end;
StreamToSend.Position := 0;
TetheringAppProfile1.Resources.FindByName('BioLife').Value := StreamToSend;
finally
CDS1.EnableControls;
ImageStream.Free;
end;
end;
Client
// Note: In the client, CDS1 has only two fields, one named ID which is an
// ftAutoInc field, and Graphic, which is a TGraphicField
procedure TApp2Form.TetheringAppProfile1Resources0ResourceReceived(const Sender:
TObject; const AResource: TRemoteResource);
var
ReceivedStream : TStream;
ImageStream : TMemoryStream;
ImageSize : Integer;
begin
AResource.Value.AsStream.Position := 0;
ReceivedStream := AResource.Value.AsStream;
ImageStream := TMemoryStream.Create;
try
if CDS1.Active then
CDS1.EmptyDataSet // discard existing data
else
CDS1.CreateDataSet;
CDS1.DisableControls;
while ReceivedStream.Position < ReceivedStream.Size - 1 do begin
ImageStream.Clear;
ReceivedStream.ReadBuffer(ImageSize, SizeOf(Integer));
ImageStream.CopyFrom(ReceivedStream, ImageSize);
CDS1.Insert;
TGraphicField(CDS1.FieldByName('Graphic')).LoadFromStream(ImageStream);
CDS1.Post;
end;
CDS1.First;
finally
ImageStream.Free;
CDS1.EnableControls;
end;
end;
Original answer follows
I have already shown you a very simple way to move images between server and client app using TClientDataSets in my answer to your q Delphi: How to Get All Images From Server Database by using App tethering?. I assumed you knew enough about Delphi programming to be able to get the data from your Sqlite db into a TCientDataSet but perhaps not.
Below is the code for the server + client of my other answer, adapted to use FireDAC components instead of TClientDataSets. Again, it uses the server dataset's SaveToStream method to save its data to the stream from the server and LoadFromStream on the client side.
Notice that there are only two lines of code in the client app.
FDApp1 code:
type
TApp1Form = class(TForm)
TetheringManager1: TTetheringManager;
TetheringAppProfile1: TTetheringAppProfile;
DBImage1: TDBImage;
btnConnect: TButton;
Label1: TLabel;
DataSource1: TDataSource;
DBGrid1: TDBGrid;
DBNavigator1: TDBNavigator;
btnSendStream: TButton;
FDConnection1: TFDConnection;
FDQuery1: TFDQuery;
FDGUIxWaitCursor1: TFDGUIxWaitCursor;
FDStanStorageBinLink1: TFDStanStorageBinLink;
procedure btnConnectClick(Sender: TObject);
procedure btnSendStreamClick(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure TetheringManager1PairedToRemote(const Sender: TObject; const
AManagerInfo: TTetheringManagerInfo);
private
procedure DataSetToStream;
end;
[...]
procedure TApp1Form.btnConnectClick(Sender: TObject);
begin
TetheringManager1.AutoConnect;
end;
procedure TApp1Form.btnSendStreamClick(Sender: TObject);
begin
DataSetToStream;
end;
procedure TApp1Form.FormCreate(Sender: TObject);
begin
Caption := Format('App1 : %s', [TetheringManager1.Identifier]);
FDQuery1.LoadFromFile('D:\D10\Samples\Data\BioLife.FDS');
end;
procedure TApp1Form.TetheringManager1PairedToRemote(const Sender: TObject; const
AManagerInfo: TTetheringManagerInfo);
begin
Label1.Caption := Format('Connected : %s %s',
[AManagerInfo.ManagerIdentifier,
AManagerInfo.ManagerName]);
end;
procedure TApp1Form.DataSetToStream;
var
Stream : TMemoryStream;
begin
Stream := TMemoryStream.Create;
FDQuery1.SaveToStream(Stream);
Stream.Position := 0;
TetheringAppProfile1.Resources.FindByName('BioLife').Value := Stream;
end;
FDApp2 code:
type
TApp2Form = class(TForm)
TetheringManager1: TTetheringManager;
TetheringAppProfile1: TTetheringAppProfile;
DataSource1: TDataSource;
DBGrid1: TDBGrid;
DBNavigator1: TDBNavigator;
DBImage1: TDBImage;
FDGUIxWaitCursor1: TFDGUIxWaitCursor;
FDMemTable1: TFDMemTable;
FDStanStorageBinLink1: TFDStanStorageBinLink;
procedure TetheringAppProfile1Resources0ResourceReceived(const Sender: TObject;
const AResource: TRemoteResource);
public
end;
[...]
procedure TApp2Form.TetheringAppProfile1Resources0ResourceReceived(const Sender:
TObject; const AResource: TRemoteResource);
begin
AResource.Value.AsStream.Position := 0;
FDMemTable1.LoadFromStream(AResource.Value.AsStream);
end;
Of course, on the client side, if for some reason you want the images (but not the other server data) copied into another dataset, you can do that by a row-by-row copy, similar to the code in your qs.