detecting windows shell changes - c

Question

I have very limited knowledge of using C Builder, could you give me an example or point me to tutorial showing how to use FindNextChangeNotification in Delphi or ,if it is possible, how to use the C component in delphi?

Answer 1

One option is use the TJvChangeNotify component, The JVCL support Delphi and C++ Builder.
Another option is use the SHChangeNotifyRegister function.
see this link Monitoring System Shell Changes using Delphi
Bye.

Answer 2

The ReadDirectoryChanges seems to be the function that I am looking for. Here is my attempt using mghie's code Why does ReadDirectoryChangesW omit events?
My objective here is to monitor the directory/path or file you will see in Unit1. I just want a simple showmessage dialogue to popup whenever a change at the location is detected. I can't find where I am supposed to pass my notification procedure or function. Unit2 just holds the unchanged code from mghie. When I compile this project and make a simple change in the directory nothing happens. I am using the ReadDirectoryChanges correctly?
here is Unit1:
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, Unit2;
type
TForm1 = class(TForm)
Button1: TButton;
Button2: TButton;
procedure FormCreate(Sender: TObject);
procedure FormDestroy(Sender: TObject);
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
fthread:TWatcherthread;
implementation
{$R *.dfm}
procedure TForm1.Button1Click(Sender: TObject);
begin
//start directory or file watch here
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
fThread := TWatcherThread.Create('C:\Users\abe\Desktop\statcious\mitsu\Demo\abc.txt');
end;
procedure TForm1.FormDestroy(Sender: TObject);
begin
if fThread <> nil then begin
TWatcherThread(fThread).Shutdown;
fThread.Free;
end;
end;
end.
Here is Unit2:
unit Unit2;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs;
type
TWatcherThread = class(TThread)
private
fChangeHandle: THandle;
fDirHandle: THandle;
fShutdownHandle: THandle;
protected
procedure Execute; override;
public
constructor Create(ADirectoryToWatch: string);
destructor Destroy; override;
procedure Shutdown;
end;
type
TForm2 = class(TForm)
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form2: TForm2;
implementation
{$R *.dfm}
constructor TWatcherThread.Create(ADirectoryToWatch: string);
const
FILE_LIST_DIRECTORY = 1;
begin
inherited Create(TRUE);
fChangeHandle := CreateEvent(nil, FALSE, FALSE, nil);
fDirHandle := CreateFile(PChar(ADirectoryToWatch),
FILE_LIST_DIRECTORY or GENERIC_READ,
FILE_SHARE_READ or FILE_SHARE_WRITE or FILE_SHARE_DELETE,
nil, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS or FILE_FLAG_OVERLAPPED, 0);
fShutdownHandle := CreateEvent(nil, FALSE, FALSE, nil);
Resume;
end;
destructor TWatcherThread.Destroy;
begin
if fDirHandle <> INVALID_HANDLE_VALUE then
CloseHandle(fDirHandle);
if fChangeHandle <> 0 then
CloseHandle(fChangeHandle);
if fShutdownHandle <> 0 then
CloseHandle(fShutdownHandle);
inherited Destroy;
end;
procedure TWatcherThread.Execute;
type
PFileNotifyInformation = ^TFileNotifyInformation;
TFileNotifyInformation = record
NextEntryOffset: DWORD;
Action: DWORD;
FileNameLength: DWORD;
FileName: WideChar;
end;
const
BufferLength = 65536;
var
Filter, BytesRead: DWORD;
InfoPointer: PFileNotifyInformation;
Offset, NextOffset: DWORD;
Buffer: array[0..BufferLength - 1] of byte;
Overlap: TOverlapped;
Events: array[0..1] of THandle;
WaitResult: DWORD;
FileName, s: string;
begin
if fDirHandle <> INVALID_HANDLE_VALUE then begin
Filter := FILE_NOTIFY_CHANGE_FILE_NAME or FILE_NOTIFY_CHANGE_DIR_NAME
or FILE_NOTIFY_CHANGE_SIZE or FILE_NOTIFY_CHANGE_LAST_WRITE;
FillChar(Overlap, SizeOf(TOverlapped), 0);
Overlap.hEvent := fChangeHandle;
Events[0] := fChangeHandle;
Events[1] := fShutdownHandle;
while not Terminated do begin
if ReadDirectoryChangesW (fDirHandle, #Buffer[0], BufferLength, TRUE,
Filter, #BytesRead, #Overlap, nil)
then begin
WaitResult := WaitForMultipleObjects(2, #Events[0], FALSE, INFINITE);
if WaitResult = WAIT_OBJECT_0 then begin
InfoPointer := #Buffer[0];
Offset := 0;
repeat
NextOffset := InfoPointer.NextEntryOffset;
FileName := WideCharLenToString(#InfoPointer.FileName,
InfoPointer.FileNameLength);
SetLength(FileName, StrLen(PChar(FileName)));
s := Format('[%d] Action: %.8xh, File: "%s"',
[Offset, InfoPointer.Action, FileName]);
OutputDebugString(PChar(s));
PByte(InfoPointer) := PByte(DWORD(InfoPointer) + NextOffset);
Offset := Offset + NextOffset;
until NextOffset = 0;
end;
end;
end;
end;
end;
procedure TWatcherThread.Shutdown;
begin
Terminate;
if fShutdownHandle <> 0 then
SetEvent(fShutdownHandle);
end;
end.