Monitor Changes to .TXT File

This example uses the System.IO.FileSystemWatcher class in the System assembly to monitor changes to a .TXT file in the C:\work\temp folder. Create the following event handler, eventhandlerChanged.m:

function eventhandlerChanged(source,arg)
disp("TXT file changed")
end

Create a FileSystemWatcher object fileObj and watch the Changed event for files with a .txt extension in the folder C:\work\temp.

file = System.IO.FileSystemWatcher("c:\work\temp");
file.Filter = "*.txt";
file.EnableRaisingEvents = true;
addlistener(file,"Changed",@eventhandlerChanged);

If you modify and save a .txt file in the C:\work\temp folder, MATLAB displays:

TXT file changed

The FileSystemWatcher documentation says that a simple file operation can raise multiple events.

To turn off the event handler, type:

file.EnableRaisingEvents = false;

Monitor Changes to Windows Form ComboBox

This example shows how to listen for changes to values in a ComboBox on a Windows^® Form. This example uses the SelectedValueChanged event defined by the System.Windows.Forms.ComboBox class.

To create this example, you must build a Windows Forms Application using a supported version of Microsoft^® Visual Studio^®.

Create a 64-bit Windows Forms Application, myForm, in your C:\work folder. Add a ComboBox control to Form1, and then add one or more items to ComboBox1. Build the application.

To add a listener to the form property, create the following MATLAB class, EnterComboData, which uses the attachListener method.

classdef EnterComboData < handle
properties
    form
end
methods
    function x = EnterComboData
        NET.addAssembly("C:\work\myForm\myForm\bin\x64\Debug\myForm.exe");
        x.form = myForm.Form1;
        Show(x.form)
        Activate(x.form)
    end
    function r = attachListener(x)
        % create listener
        r = addlistener(
            x.form.Controls.Item(0),
            "SelectedValueChanged",
            @x.anyChange);
    end
    function anyChange(~,~,~)
        % listener action if comboBox changes
        disp("Field updated")
    end
end
end

To execute the following MATLAB commands, you must create and load the application named myForm.exe. To create a form and call its attachListener method, use the EnterComboData class.

form = EnterComboData;
form.attachListener;

To trigger an event, select an item from the drop-down menu on the ComboBox. MATLAB displays:

Field updated