MATLAB: Using .NET FileSystemWatcher to listen for new files

filesystemwatcherlistenernet

Hi,
I want to write a simple program that runs continuously and listens for the FileSystemWatcher events i.e. a new file has appeared in a folder. When the file arrives I want to process that file in some way. The following is code that I have been playing with:
function ImageSorter
%Start listeners for file new notifications
   fileObj = System.IO.FileSystemWatcher('C:\Dicom\');
   fileObj.EnableRaisingEvents = true;
   l1 = addlistener(fileObj, 'Created', @eventhandlerChanged);
%now I want the program to stop and listen for the events and not 
% continue to the end.
   h = figure('visible','off');
   waitfor(h);
   delete(l1);
end
function eventhandlerChanged(source,arg)
    arg.FullPath
end
If I insert a break point at the end of the ImageSorter program then it works and the eventhandlerChanged function is called when a new file appears in the folder C:\DICOM.
How do I make the function stop running to the end and wait for the listening events?
Jonathan

Best Answer

Jonathon, Here is an example of how to do it. Note you need to listen on the changed event and not the created event
function FileWatch(pathToWatch)
txtDetectedFiles = createFigure;
fileObj = System.IO.FileSystemWatcher(pathToWatch);
fileObj.EnableRaisingEvents = true;
changeListener =addlistener(fileObj, 'Changed', @onChange); %need to keep in scope
    function txtDetectedFiles = createFigure
        figHdl = figure('Name','FileWatcher',...
                              'Menubar','none',...
                              'Toolbar','none',...
                              'NumberTitle','off',...
                              'Units','normalized',...
                              'Position',[0.4,0.4,0.4,0.2]);
        uicontrol('Parent',figHdl,...
                     'Style','text',...
                     'Units','normalized',...
                     'Position',[0.1,0.9,0.8,0.08],...
                     'String',['Path Watched: ',pathToWatch]);
        uicontrol('Parent',figHdl,...
                      'Style','pushbutton',...
                      'String','Write a file to the watched path.',...
                      'Units','normalized',...
                      'Position',[0.1,0.6,0.5,0.2],...
                      'Callback',@cmdWriteFile);
        txtDetectedFiles = uicontrol('Parent',figHdl,...
                                                 'Style','edit',...
                                                 'Enable','inactive',...
                                                 'Units','normalized',...
                                                 'Position',[0.1,0.05,0.8,0.45],...
                                                 'Max',3);
    end %createFigure
    function cmdWriteFile(varargin)
        %create a simple text file in the watched folder
        tName = tempname;
        [~,tName] = fileparts(tName);
        fName =fullfile(pathToWatch,[tName,'.txt']);
        dlmwrite(fName,1:5);
    end %cmdWriteFile
    function onChange(~,evt)
        existStr = get(txtDetectedFiles,'String');
        if isempty(existStr)
            existStr = {};
        end %if
        existStr{length(existStr)+1} = ['New file Detected: ',char(evt.FullPath.ToString())];
        set(txtDetectedFiles,'String',existStr);
    end %onChange
end %FileWatch
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