TDownloadURL cannot download from HTTPS

问题:

I've been trying to create (TFileStream) a PDF through the TDownloadURL class, but I'm really having troubles in obtaining the file/stream from the URL, specially if the URL a HTTPS.

I'm not sure if I was clear, but I will post a snippet so it might help understanding:

implementation
var pdfStreamed: TDownloadUrl;
var fileStream : TFileStream;
  procedure generateStream;
  begin
    pdfStreamed:= TDownLoadURL.Create(nil);
    with pdfStreamed do
      begin
        URL := 'https://farm9.staticflickr.com/8327/8106108098_08e298f0d9_b.jpg'; //stream;
        FileName := 'D:\';
        ExecuteTarget(nil);
//        Execute;
      end;
  end;

The URL property exists both in HTTP as in HTTPS! But it throws me an error: Exception class Exception with message 'Error downloading URL: https://farm9.staticflickr.com/8327/8106108098_08e298f0d9_b.jpg'.

Could point what am I doing wrong? I've searched a lot for this, but couldn't find anything that work and simple!

Thanks a lot!

回答1:

TDownloadURL is just a thin wrapper around Microsoft's URLDownloadToFile() function, which supports HTTPS just fine.

TDownloadURL does not tell you why URLDownloadToFile() fails, unfortunately. However, I can see that you are setting the FileName property to just a folder path, but you need to instead set it to the full path and filename of the destination file that is going to be created to hold the downloaded data. IOW, change this:

FileName := 'D:\';

To this:

FileName := 'D:\8106108098_08e298f0d9_b.jpg';

回答2:

Use Remy's answer of changing the file name to specify the correct place to save, but to fix, change your ExecuteTarget line to something like

ExecuteTarget(Self);

I just tried your code with those two changes, and it successfully downloaded the image. Essentially, the component needs a handle to reference as from Here