CODEWITHSUNDEEP
delphilistviewfiledrag-and-drophandle
Nanik
Nanik

Reputation: 43

Delphi - Drag & Drop with ListView

Good evening :-)!

I have this code to use Drag & Drop method for files:

TForm1 = class(TForm)
...
public
    procedure DropFiles(var msg: TMessage ); message WM_DROPFILES;
end;

procedure TForm1.FormCreate(Sender: TObject)
begin
    DragAcceptFiles(ListView1.Handle, True);
end;

procedure TForm1.DropFiles(var msg: TMessage );
var
  i, count  : integer;
  dropFileName : array [0..511] of Char;
  MAXFILENAME: integer;
begin
  MAXFILENAME := 511;
  count := DragQueryFile(msg.WParam, $FFFFFFFF, dropFileName, MAXFILENAME);
  for i := 0 to count - 1 do
  begin
    DragQueryFile(msg.WParam, i, dropFileName, MAXFILENAME);
    Memo1.Lines.Add(dropFileName);
  end;
  DragFinish(msg.WParam);
end;

In area of ListView is DragCursor, but in Memo1 aren't any records. When I use for example ListBox and method DragAcceptFiles(ListBox1.Handle, True) ever is fine.

ListView property DragMode I set to dmAutomatic.

Thanks :-)

Upvotes: 4

Views: 6222

Answers (2)

Andreas Hausladen
Andreas Hausladen

Reputation: 8141

You've called DragAcceptFiles for the ListView, so Windows sends the WM_DROPFILES to your ListView and not to your Form. You have to catch the WM_DROPFILES message from the ListView.

  private
    FOrgListViewWndProc: TWndMethod;
    procedure ListViewWndProc(var Msg: TMessage);
  // ...
  end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  // Redirect the ListView's WindowProc to ListViewWndProc
  FOrgListViewWndProc := ListView1.WindowProc;
  ListView1.WindowProc := ListViewWndProc;

  DragAcceptFiles(ListView1.Handle, True);
end;

procedure TForm1.ListViewWndProc(var Msg: TMessage);
begin
  // Catch the WM_DROPFILES message, and call the original ListView WindowProc 
  // for all other messages.
  case Msg.Msg of
    WM_DROPFILES:
      DropFiles(Msg);
  else
    if Assigned(FOrgListViewWndProc) then
      FOrgListViewWndProc(Msg);
  end;
end;

Upvotes: 8

Sertac Akyuz
Sertac Akyuz

Reputation: 54772

Your problem is, you're registering the list view window as a drop target, but handling the WM_DROPFILES message in the form class. The message is sent to the list view control, you should handle the message there.

Upvotes: 1

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