This example shows the usage of TSxChangeNotifier component. Use this component if you have a need to monitor file modification, creation or deletion. The component allows you to monitor a single file as well as a group of files, you can use masks and monitor several directories in the folders tree. When file event occurs the TSxChangeNotifier calls corresponding event handler and reports the name of file that was changed.

    The example below shows how to use TSxChangeNotifier to monitor all files in a single directory.

    Create a new project: File -> New... -> Application and drop the TSxChangeNotifier onto its main form. Then add a couple of controls as shown below (you can download a ready example using a links below):

    Save the project now.

    The next step is a configuration of TSxChangeNotifier properties. Use the data from the table below to set the properties:

Set button's event handlers now.  Code for the "Start" button is:

procedure TTestNotifierWindow.StartClick(Sender: TObject);
begin
  ChangeNotifier.Start;
end;

  The following code should be used for the "Stop" button:

procedure TTestNotifierWindow.StartClick(Sender: TObject);
begin
  ChangeNotifier.Stop;
end;

  The "Pause" works as:

procedure TTestNotifierWindow.btnPauseResumeClick(Sender: TObject);
begin
  if not ChangeNotifier.Paused then
  begin
    ChangeNotifier.Paused:=True;
    btnPauseResume.Caption:='Resume';
  end
  else
  begin
    ChangeNotifier.Paused:=False;
    btnPauseResume.Caption:='Pause';
  end;
end;

     The next handler is for "Clear" button:

procedure TTestNotifierWindow.StartClick(Sender: TObject);
begin
  ListView.Items.Clear;
end;

     Now it is a time to add code to component's event handlers. All three handlers are similar. The AddFile event should look like:

procedure TTestNotifierWindow.ChangeNotifierAddFile(Sender: TObject;
  FileInfo: TSxFileInfoEventData);
var
  ListItem:TListItem;
begin
  ListItem:=ListView.Items.Add;
  ListItem.Caption:='Created';
  ListItem.SubItems.Add(FileInfo.Filename);
  ListItem.SubItems.Add(DateTimeToStr(FileInfo.NewLastAccessTime));
end;

     The TSxChangeNotifier.OnChange event is handled as:

procedure TTestNotifierWindow.ChangeNotifierChange(Sender: TObject;
  FileInfo: TSxFileInfoEventData);
var
  ListItem:TListItem;
begin
  ListItem:=ListView.Items.Add;
  ListItem.Caption:='Modified';
  ListItem.SubItems.Add(FileInfo.Filename);
  ListItem.SubItems.Add(DateTimeToStr(FileInfo.OldLastWriteTime));
end;

     And the TSxChangeNotifier.OnDelete event should contain a code:

procedure TTestNotifierWindow.ChangeNotifierDelete(Sender: TObject;
  FileInfo: TSxFileInfoEventData);
var
  ListItem:TListItem;
begin
  ListItem:=ListView.Items.Add;
  ListItem.Caption:='Deleted';
  ListItem.SubItems.Add(FileInfo.Filename);
  ListItem.SubItems.Add(DateTimeToStr(FileInfo.OldLastAccessTime));
end;

    Save the project and compile it - it is ready now! Launch it and press the "Start" button. First of all the application will search for files that match the mask and will collect their data into internal database. These data will be used later to monitor changes.

    You can save this database to avoid re-scanning when application restarts. Use the PersistentRoot и RootImageFileName properties to do it. When the monitoring is stopped the database is dumped into the file, when monitoring is restarted the database will be restored. Another use of this feature - you can monitor changes even if the monitoring process was restarted.

    Use links below to download source codes of this example as well as binary files:

  Top