**Course Title:** MATLAB Programming: Applications in Engineering, Data Science, and Simulation **Section Title:** Application Development with MATLAB **Topic:** Event-driven programming and callback functions. ## Introduction to Event-driven Programming Event-driven programming is a paradigm where the flow of a program is determined by events or user interactions. In MATLAB, event-driven programming allows you to create interactive applications that respond to specific events, such as button clicks, mouse movements, or keyboard input. This topic introduces you to event-driven programming in MATLAB using callback functions. ## Understanding Callback Functions Callback functions are the backbone of event-driven programming in MATLAB. A callback function is a function that is executed in response to a specific event or user interaction. When an event occurs, MATLAB calls the associated callback function, which then handles the event. ### Types of Callbacks There are several types of callbacks in MATLAB, including: 1. **Button-down callback**: Triggered when a button is clicked. 2. **Button-up callback**: Triggered when a button is released. 3. **Key-press callback**: Triggered when a key is pressed. 4. **Mouse-motion callback**: Triggered when the mouse is moved. 5. **Mouse-click callback**: Triggered when the mouse is clicked. ## Using Callback Functions in MATLAB To use callback functions in MATLAB, you need to follow these steps: 1. **Create a callback function**: Define a function that handles the event. 2. **Set the callback property**: Set the `Callback` property of the object (e.g., button, figure) to the name of the callback function. 3. **Trigger the event**: The event is triggered, and MATLAB calls the callback function. ### Example 1: Basic Button Callback Create a simple GUI with a button that displays a message box when clicked: ```matlab % Create a figure and button f = figure; b = uicontrol(f, 'Style', 'pushbutton', 'String', 'Click me!'); % Set the callback property set(b, 'Callback', @callback_Function); % Define the callback function function callback_Function(hObject, eventdata) msgbox('You clicked the button!'); end ``` ### Example 2: Passing Arguments to Callback Functions Create a GUI with a button that accepts user input and displays a message box with the input value: ```matlab % Create a figure, button, and edit box f = figure; b = uicontrol(f, 'Style', 'pushbutton', 'String', 'Enter value'); e = uicontrol(f, 'Style', 'edit'); % Set the callback property set(b, 'Callback', @(src, eventdata) callback_Function(src, eventdata, get(e, 'String'))); % Define the callback function function callback_Function(hObject, eventdata, value) msgbox(['You entered: ', value]); end ``` ### Example 3: Using Anonymous Functions as Callbacks Create a GUI with a button that uses an anonymous function as a callback: ```matlab % Create a figure and button f = figure; b = uicontrol(f, 'Style', 'pushbutton', 'String', 'Click me!'); % Set the callback property to an anonymous function set(b, 'Callback', @(src, eventdata) disp('You clicked the button!')); ``` ## Advanced Topics ### Using `appdata` to Share Data between Callback Functions In MATLAB, `appdata` is a mechanism for storing and accessing data that is shared between callback functions. You can use `appdata` to store data that needs to be accessed by multiple callback functions. ### Using ` guidata` to Store GUI Data `guidata` is a function that allows you to store and retrieve data associated with a GUI. You can use `guidata` to store data that is specific to a particular GUI. ## Conclusion Event-driven programming using callback functions is a powerful tool for creating interactive applications in MATLAB. By understanding callback functions and how to use them, you can create GUIs that respond to user interactions and perform complex tasks. ## Practical Takeaways * Understand the concept of event-driven programming and callback functions. * Learn how to create and use callback functions in MATLAB. * Use `appdata` and `guidata` to share data between callback functions and store GUI data. * Practice creating interactive GUIs using callback functions. ## External Resources * MATLAB Documentation: [Callback Functions](https://www.mathworks.com/help/matlab/creating_flexible_callbacks.html) * MATLAB Documentation: [Using `appdata` to Share Data](https://www.mathworks.com/help/matlab/using-appdata-to-share-data.html) * MATLAB Documentation: [Using `guidata` to Store GUI Data](https://www.mathworks.com/help/matlab/using-guidata-to-store-gui-data.html) ## What's Next? In the next topic, we will cover packaging and deploying standalone MATLAB applications. This will include how to use MATLAB's built-in tools to package and deploy your applications, as well as how to create standalone executables. If you have any questions or need further clarification on any of the topics covered in this section, please feel free to ask.

% Create a figure and button
f = figure;
b = uicontrol(f, 'Style', 'pushbutton', 'String', 'Click me!');

% Set the callback property
set(b, 'Callback', @callback_Function);

% Define the callback function
function callback_Function(hObject, eventdata)
    msgbox('You clicked the button!');
end

% Create a figure, button, and edit box
f = figure;
b = uicontrol(f, 'Style', 'pushbutton', 'String', 'Enter value');
e = uicontrol(f, 'Style', 'edit');

% Set the callback property
set(b, 'Callback', @(src, eventdata) callback_Function(src, eventdata, get(e, 'String')));

% Define the callback function
function callback_Function(hObject, eventdata, value)
    msgbox(['You entered: ', value]);
end

% Create a figure and button
f = figure;
b = uicontrol(f, 'Style', 'pushbutton', 'String', 'Click me!');

% Set the callback property to an anonymous function
set(b, 'Callback', @(src, eventdata) disp('You clicked the button!'));