UI components in MATLAB - Step-by-Step Execution

Concept Flow - UI components

Create UIFigure

↓

Add UI Components

↓

Set Properties

↓

Display UI

↓

User Interaction

↓

Callbacks Triggered

↓

Update UI or Data

↓

End or Repeat Interaction

This flow shows how a MATLAB UI starts with a figure, adds components, sets properties, displays the UI, and handles user interactions with callbacks.

Execution Sample

MATLAB

fig = uifigure();
btn = uibutton(fig, 'Text', 'Click Me');
btn.ButtonPushedFcn = @(btn,event) disp('Button clicked');

Creates a UI figure with a button that prints a message when clicked.

Execution Table

Step	Action	Variable State	Output/Effect
1	Create UI figure	fig = UIFigure object	Window appears
2	Add button to fig	btn = UIButton object linked to fig	Button appears on window
3	Set button text	btn.Text = 'Click Me'	Button label set
4	Assign callback to button	btn.ButtonPushedFcn set	Button ready to respond
5	User clicks button	No variable change	Console prints 'Button clicked'
6	No further action	State unchanged	Waiting for next interaction

💡 Execution waits for user interaction; program runs until UI is closed.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	Final
fig	undefined	UIFigure object	UIFigure object	UIFigure object	UIFigure object	UIFigure object	UIFigure object
btn	undefined	undefined	UIButton object	UIButton object with Text='Click Me'	UIButton object with callback	UIButton object with callback	UIButton object with callback

Key Moments - 3 Insights

Why doesn't the button do anything immediately after creation?

Because the callback function is only triggered when the user clicks the button, as shown in step 5 of the execution_table.

What is the role of the UIFigure object 'fig'?

It acts as the main window container for UI components, created in step 1 and used to parent the button in step 2.

How does MATLAB know what to do when the button is clicked?

The callback function assigned in step 4 tells MATLAB what code to run on button click, which is executed in step 5.

Visual Quiz - 3 Questions

Look at the execution_table, what is the state of 'btn' after step 3?

A Undefined

B UIButton object without text

C UIButton object with Text='Click Me'

D UIFigure object

💡 Hint

Check the 'Variable State' column for step 3 in the execution_table.

At which step does the program print 'Button clicked' to the console?

A Step 5

B Step 4

C Step 2

D Step 6

💡 Hint

Look at the 'Output/Effect' column in the execution_table for the printing action.

If we remove the callback assignment in step 4, what happens when the button is clicked?

A Button text changes automatically

B Nothing happens on click

C UIFigure closes

D Error message appears

💡 Hint

Refer to the key_moments explanation about callbacks and step 5 in the execution_table.

Concept Snapshot

UI Components in MATLAB:
- Create a UIFigure as main window
- Add components like buttons with uibutton
- Set properties (e.g., Text)
- Assign callbacks for interaction
- UI waits for user events
- Callbacks run code on events

Full Transcript

This visual execution trace shows how MATLAB UI components work step-by-step. First, a UIFigure window is created to hold UI elements. Then, a button is added to this figure and its text label is set. A callback function is assigned to the button to define what happens when it is clicked. When the user clicks the button, the callback runs and prints a message to the console. Variables 'fig' and 'btn' track the UI figure and button objects through these steps. Beginners often wonder why the button does nothing until clicked; this is because the callback triggers only on user action. The UIFigure acts as the container for all UI components. Without assigning a callback, clicking the button has no effect. This trace helps learners see how UI components are created, configured, and respond to user interaction in MATLAB.

Practice

1. Which MATLAB function is used to create a new interactive window for UI components?

easy

A. window

B. uifigure

C. uiwindow

D. figure

Solution

1. Step 1: Understand the purpose of UI windows

   MATLAB uses a special function to create windows that support interactive UI components like buttons and sliders.

2. Step 2: Identify the correct function for UI windows

   The function uifigure creates a window designed for UI components, unlike figure which is for plots.

3. Final Answer:

   uifigure -> Option B

4. Quick Check:

   UI window = uifigure [OK]

Hint: Use uifigure for UI windows, not figure [OK]

Common Mistakes:

• Confusing uifigure with figure
• Using non-existent functions like uiwindow
• Assuming window creates UI windows

2. Which of the following is the correct syntax to add a button to a UI figure named fig?

easy

A. btn = uibutton();

B. btn = button(fig);

C. btn = addbutton(fig);

D. btn = uibutton(fig);

Solution

1. Step 1: Recall the function to create buttons in UI figures

   MATLAB uses uibutton to create buttons inside a UI figure.

2. Step 2: Check the syntax for specifying the parent UI figure

   The parent figure must be passed as an argument to uibutton, so uibutton(fig); is correct.

3. Final Answer:

   btn = uibutton(fig); -> Option D

4. Quick Check:

   Button creation = uibutton(fig) [OK]

Hint: Always pass the figure handle to uibutton [OK]

Common Mistakes:

• Using button() instead of uibutton()
• Not passing the figure as argument
• Using non-existent addbutton() function

3. What will be the output when running this code?

fig = uifigure();
btn = uibutton(fig, 'Text', 'Click Me');
disp(btn.Text);

medium

A. Click Me

B. uibutton

C. btn

D. Error: Text property not found

Solution

1. Step 1: Understand button creation with text

   The button is created with the text property set to 'Click Me'.

2. Step 2: Display the button's Text property

   Using disp(btn.Text) prints the string assigned to the Text property.

3. Final Answer:

   Click Me -> Option A

4. Quick Check:

   Button text = 'Click Me' [OK]

Hint: disp(btn.Text) shows button label text [OK]

Common Mistakes:

• Expecting the variable name instead of text
• Thinking btn.Text is invalid property
• Confusing output with object type

4. Identify the error in this code snippet:

fig = uifigure();
btn = uibutton(fig);
btn.Callback = @(src,event) disp('Button clicked');

medium

A. Property name should be ButtonPushedFcn, not Callback

B. uifigure() cannot have buttons

C. Anonymous functions cannot be used as callbacks

D. disp cannot be used inside callbacks

Solution

1. Step 1: Check the correct callback property for uibutton

   In MATLAB UI buttons, the callback property is named ButtonPushedFcn, not Callback.

2. Step 2: Understand the effect of wrong property name

   Assigning to Callback does nothing; the button won't respond to clicks.

3. Final Answer:

   Property name should be ButtonPushedFcn, not Callback -> Option A

4. Quick Check:

   Button callback = ButtonPushedFcn [OK]

Hint: Use ButtonPushedFcn for button callbacks [OK]

Common Mistakes:

• Using Callback instead of ButtonPushedFcn
• Thinking anonymous functions are invalid
• Believing buttons can't be added to uifigure

5. You want to create a UI with a slider that updates a label text showing the slider value in real-time. Which approach correctly sets this up?

hard

A. Create slider and label, then use a loop to constantly check slider.Value and update label.Text

B. Create slider and label, then set label's ValueChangedFcn to update slider.Value inside the callback

C. Create slider and label, then set slider's ValueChangedFcn to update label.Text inside the callback

D. Create slider and label, then set slider's ButtonPushedFcn to update label.Text

Solution

1. Step 1: Understand slider and label interaction

   The slider's ValueChangedFcn triggers when the slider moves, perfect for updating the label.

2. Step 2: Set callback to update label text

   Inside the slider's callback function, update the label's Text property to show the current slider value.

3. Final Answer:

   Create slider and label, then set slider's ValueChangedFcn to update label.Text inside the callback -> Option C

4. Quick Check:

   Slider update uses ValueChangedFcn callback [OK]

Hint: Use slider's ValueChangedFcn to update label text [OK]

Common Mistakes:

• Using label's ValueChangedFcn instead of slider's
• Using ButtonPushedFcn on slider (not valid)
• Using loops instead of callbacks