Mega Code Archive
Drag and drop files into delphi
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This code demonstrates how to drag files from Windows into a Delphi-application. The source application could be anything with drag&drop functionality: Explorer, OutLook, WinZip...
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls;
type
TForm1 = class(TForm)
Memo1: TMemo;
procedure FormCreate(Sender: TObject);
private
// The drop action is trapped by looking for WM_DropFiles messages
procedure FileIsDropped(var Msg: TMessage); message WM_DropFiles;
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
uses ShellAPI;
{$R *.DFM}
procedure TForm1.FormCreate(Sender: TObject);
begin
// Tell Windows that this form accept dragged files
DragAcceptFiles(Handle, true);
end;
procedure TForm1.FileIsDropped(var Msg: TMessage);
var
Drop: THandle;
FileName: array[0..254] of Char;
NumberOfFiles: integer;
FileCounter: integer;
begin
Drop:= Msg.WParam;
// If the indexno is 4294967295, the number of dragged items will be retrieved
// with DragQueryFile command.
// ( The API-manual tells me that the indexno should be -1, which is not a
// possible Cardinal-value. 4294967295 is the maximum Cardinal-value, and it
// seems to work fine!? Could anybody give me a hint about this? )
NumberOfFiles:= DragQueryFile(Drop, 4294967295, FileName, 254);
for FileCounter:= 0 to NumberOfFiles - 1 do
begin
// Copy the filename,-s with the corresponding value to the buffer FileName.
DragQueryFile(Drop, FileCounter, FileName, 254);
// Write the filename (without path) to Memo.
Memo1.Lines.Add(ExtractFileName(FileName));
end;
// Release memory that Windows allocated for use in transferring filenames to
// the application.
DragFinish(Drop);
end;
end.
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