John Barrat wrote:
> I'm dragging and dropping files from Explorer to my Application using the
> ShellAPI unit.
>
> On my form I have a listbox to which I want to drag files.
>
> In form.create I add
>
> DragAcceptFiles(lstFiles.Handles, True); //where lstFiles is my list box.
>
> This appears to work - i.e. cursor changes to Accept drop but the
> WM_DROPFILES message is not received.
>
> If I use the form's handle it works but of course the Accept Drop Cursor
> appears anywhere on the form.
>
> The form is not the main form of the application and is brought up as a
> modal dialog. I have the same code running successfully with a listbox
> control on the Main form in another application. Could this be the
> difference?
>
> Also, how do I determine what files are attempting to be dropped? Ideally I
> would like to test what was being dropped while it was being dragged and
> only show the Accept Drop mouse cursor when files of the correct type were
> being dropped.
I've appended a simple unit that shows how you can tweak TListBox
to recognize Shell drag and drop. This should get you started,
but you're welcome to Email me if this gives you any trouble.
I've used what I call an "interposer" class to implement this
quickly; but if you're going to be using this a lot, there may
some percentage in wrapping this functionality into a new component.
Alternatively you might care to download the old TurboPower
ShellShock library off SourceForge, it has a component to attach
shell drag-drop functionality to any windowed control.
HTH
Stephen Posey
[EMAIL PROTECTED]
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unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics,
Controls, Forms,
Dialogs, StdCtrls,
ShellAPI;
type
TListBox = class(StdCtrls.TListBox)
procedure WMDropFiles(var Msg: TWMDropFiles);
message WM_DROPFILES;
end;
TForm1 = class(TForm)
ListBox1: TListBox;
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
procedure TForm1.FormCreate(Sender: TObject);
begin
DragAcceptFiles( ListBox1.Handle, True );
end;
{ TListBox }
procedure TListBox.WMDropFiles(var Msg: TWMDropFiles);
var
Count: Integer;
i: Integer;
Buff: array [0..255] of Char;
S: string;
begin
// passing $FFFFFFFF for the second parameter
// returns a count of dropped files
Count := DragQueryFile(Msg.Drop, $FFFFFFFF, nil, 0);
ShowMessage(IntToStr(Count) + ' file(s) dropped.');
for i := 0 to Count-1 do begin
DragQueryFile(Msg.Drop, i, @Buff[0], SizeOf(Buff));
S := Buff;
Items.Add( S );
end;
end;
end.
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