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Code Examples

How to use drag'n'drop feature for accept files dropped from Explorer?

type
  TMainForm = class(TForm)
  ...
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  ...
  private
    procedure WMDropFiles(var Msg: TWMDROPFILES); message WM_DROPFILES;
  ...
  end;

 ...
procedure TMainForm.FormCreate(Sender: TObject);
begin
{ files acceptor registration }
  DragAcceptFiles(MainForm.WindowHandle, True);
end;

procedure TMainForm.FormDestroy(Sender: TObject);
begin
{ files acceptor unregistration }
  DragAcceptFiles(MainForm.WindowHandle, False);
end;

procedure TMainForm.WMDropFiles(var Msg: TWMDropFiles);
var
  CFileName: array [0..MAX_PATH] of Char;
  WhichFiles: TStringList;
  I, FilesCount: Integer;
begin
  WhichFiles := TStringList.Create;
  try
    FilesCount := DragQueryFile(Msg.Drop, $FFFFFFFF, CFileName, MAX_PATH);
    for I := 0 to Pred(FilesCount) do
    begin
      if DragQueryFile(Msg.Drop, I, CFileName, MAX_PATH) > 0 then
      begin
        WhichFiles.Add(CFileName);
      end;
    end;

    if WhichFiles.Count > 0 then
    begin
      Screen.Cursor := crHourGlass;
      for I := 0 to Pred(WhichFiles.Count) do
      begin
        { your code for processing list of filenames }
      end;
      Screen.Cursor := crDefault;
    end;
  finally
    DragFinish(Msg.Drop);
    WhichFiles.Free;
  end;
end;