UI components in MATLAB - Mini Project: Build & Apply

Building a Simple MATLAB UI with Buttons and Text

📖 Scenario: You are creating a simple user interface (UI) in MATLAB to greet users. The UI will have a button and a text label. When the button is clicked, the text label will change to say "Hello, User!".

🎯 Goal: Build a MATLAB UI with a button and a text label. When the button is clicked, the label updates to greet the user.

📋 What You'll Learn

Create a figure window named fig

Add a button named btn with the label "Click Me"

Add a text label named txt with initial text "Waiting..."

Write a callback function named buttonCallback that changes the text label to "Hello, User!" when the button is clicked

Assign the callback function to the button's ButtonPushedFcn property

💡 Why This Matters

🌍 Real World

Creating simple graphical user interfaces helps users interact with programs easily without typing commands.

💼 Career

UI programming skills are useful for engineers and scientists who build tools for data visualization and user interaction.

1

Create the main figure window

Create a figure window and assign it to a variable called fig using uifigure.

MATLAB

# Create a figure window and assign it to 'fig'
# Your code here

Hint

Use fig = uifigure(); to create the window.

2

Add a button and a text label

Add a button to fig named btn with the text "Click Me" using uibutton. Also add a text label named txt with the initial text "Waiting..." using uilabel.

MATLAB

fig = uifigure();
# Add a button named 'btn' with text "Click Me"
# Add a text label named 'txt' with text "Waiting..."
# Your code here

Hint

Use uibutton(fig, 'Text', 'Click Me') and uilabel(fig, 'Text', 'Waiting...').

3

Write the button callback function

Write a function named buttonCallback that takes two inputs (src and event) and changes the txt.Text property to "Hello, User!".

MATLAB

fig = uifigure();
btn = uibutton(fig, 'Text', 'Click Me');
txt = uilabel(fig, 'Text', 'Waiting...');

# Write the function 'buttonCallback' below
# Your code here

Hint

Define buttonCallback with inputs src and event. Change txt.Text inside.

4

Connect the button to the callback and run

Set the button's ButtonPushedFcn property to the function handle @buttonCallback. Then run the program and observe the output when clicking the button.

MATLAB

fig = uifigure();
btn = uibutton(fig, 'Text', 'Click Me');
txt = uilabel(fig, 'Text', 'Waiting...');

function buttonCallback(src, event)
    txt.Text = 'Hello, User!';
end

# Assign the callback to the button
# Your code here

Hint

Use btn.ButtonPushedFcn = @buttonCallback; to link the button to the function.

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