How to Use wm_dropfiles messages? On the same interface, how can multiple components support Windows external file drag and drop at the same time. Dragacceptfiles.

How to Use wm_dropfiles messages? On the same interface, how can multiple components support Windows external file drag and drop at the same time. Dragacceptfiles. Delphi/Windows SDK/API
Http://www.delphi2007.net/DelphiAPI/html/delphi_20061114152826236.html
Unit unit1;
Interface
Uses
Windows, messages, sysutils, variants, classes, graphics, controls, forms,
Dialogs, extctrls, shellapi;
Type
Tform1 = Class (tform)
Panel1: tpanel;
Procedure formcreate (Sender: tobject );
Private
Oldwndproc: twndmethod;
Procedure dragfileproc (var msg: tmessage); message wm_dropfiles;
Public
{Public declarations}
End;
VaR
Form1: tform1;
Implementation
{$ R *. DFM}
{Tform1}

Procedure tform1.dragfileproc (var msg: tmessage );
VaR
Filename: array [0 .. MAX_PATH-1] of char;
Sfilename: string;
Count: integer;
Begin
If msg. MSG = wm_dropfiles then
Begin
Count: = dragqueryfile (msg. wparam, $ ffffffff, @ filename [0], max_path); // get the number of Drag and Drop files
If count> 0 then
Begin
Fillchar (filename, sizeof (filename), #0 );
Dragqueryfile (msg. wparam, 0, @ filename [0], max_path); // query the file name
Sfilename: = string (filename );

End;
Dragfinish (msg. wparam); // release the resources used
End else
Oldwndproc (MSG );
End;

Procedure tform1.formcreate (Sender: tobject );
Begin
Dragacceptfiles (panel1.handle, enabled );
Oldwndproc: = panel1.windowproc; // Save the original windowproc
Panel1.windowproc: = dragfileproc; // set the new windowproce
End;

End.

I would like to ask, if I have multiple wincontrol components on one interface at the same time and need to support Windows external file drag and drop, what should I do?

Through (var msg: tmessage); message wm_dropfiles; can you determine which component is returned?

Can I add a method for tpanel to receive wm_dropfiles.
The premise is that you do not need to re-compile the tpanel control. Writing an inheritance class cannot be placed on the interface. Unless compiled into a visual control.

Uses
Stdctrls, shellapi;


Type

Tdragmemo = Class (tmemo)
Procedure dragfileproc (var msg: tmessage); message wm_dropfiles;
End;

Tform1 = Class (tform)
Procedure formcreate (Sender: tobject );
Private
{Private Declarations}
Public
{Public declarations}
End;

VaR
Form1: tform1;

Implementation

{$ R *. DFM}

Procedure tform1.formcreate (Sender: tobject );
VaR
Memo: tdragmemo;
Begin
Memo: = tdragmemo. Create (NiL );
Memo. Parent: = self;
End;

Procedure tdragmemo. dragfileproc (var msg: tmessage );
Begin
// Your code
End;

End.

The above is just to define a class. You can make it a control, inherit the Windows Control directly, and then modify dragfileproc.

Woshihaoge (fragmented) I know.
But in this case, if you want to directly put it on the interface, you need to make the control.

I want edit, panel, listview... and other controls to support the drag and drop of EXPLORER. It feels a bit like this ....

Are there other methods?

There is no way. It can only be subclass like this, or it can be made into a control. I have studied similar issues before. It seems that this method is described in the book.

Can someone answer this question?