Question

How to download a file from internet with progress bar using threads in Delphi 2009/10 without Indy components?

Answer 1

This uses the clever internet suite to handle the download, I haven’t so much as checked it in the IDE so I wouldn’t expect it to compile and no doubt it’s full of errors but it should be enough to get you started.

I don’t know why you don’t want to use Indy but I would strongly advise getting some components to help with the Http download… there really is no need to reinvent the wheel.

interface
type
    TMyDownloadThread= Class(TThread)
    private
        FUrl: String;
        FFileName: String;
        FProgressHandle: HWND;
        procedure GetFile (Url: String; Stream: TStream; ReceiveProgress: TclSocketProgressEvent);
        procedure OnReceiveProgress(Sender: TObject; ABytesProceed, ATotalBytes: Integer);
        procedure SetPercent(Percent: Double);
    protected
        Procedure Execute; Override;
    public
        Constructor Create(Url, FileName: String; PrograssHandle: HWND);
    End;

implementation

constructor TMyDownloadThread.Create(Url, FileName: String; PrograssHandle: HWND);
begin
    Inherited Create(True);
    FUrl:= Url;
    FFileName:= FileName;
    FProgressHandle:= PrograssHandle;
    Resume;
end;


procedure TMyDownloadThread.GetFile(Url: String; Stream: TStream; ReceiveProgress: TclSocketProgressEvent);
var
    Http: TclHttp;
begin
    Http := TclHTTP.Create(nil);
    try
        try
            Http.OnReceiveProgress := ReceiveProgress;
            Http.Get(Url, Stream);
        except
        end;
    finally
        Http.Free;
    end;
end;

procedure TMyDownloadThread.OnReceiveProgress(Sender: TObject; ABytesProceed, ATotalBytes: Integer);
begin
    SetPercent((ABytesProceed / ATotalBytes) * 100);
end;

procedure TMyDownloadThread.SetPercent(Percent: Double);
begin
    PostMessage(FProgressHandle, AM_DownloadPercent, LowBytes(Percent), HighBytes(Percent));
end;

procedure TMyDownloadThread.Execute;
var
    FileStream: TFileStream;
begin
    FileStream := TFileStream.Create(FFileName, fmCreate);
    try
        GetFile(FUrl, FileStream, OnReceiveProgress);
    finally
        FileStream.Free;
    end;        
end;