UI components in MATLAB

Introduction

UI components help you build simple windows and controls to interact with your data. They make your program easy to use by adding buttons, sliders, and text boxes.

You want to create a small app to explore data visually.

You need buttons to run different analysis steps without typing commands.

You want users to enter values or select options easily.

You want to show results or messages in a window.

You want to build a tool that anyone can use without coding.

Syntax

MATLAB

fig = uifigure;
btn = uibutton(fig, 'Text', 'Click me');
slider = uislider(fig);
label = uilabel(fig, 'Text', 'Value:');

uifigure creates a new window.

Other components like uibutton, uislider, and uilabel add controls inside the window.

Examples

This creates a window with a button labeled 'Press'.

MATLAB

fig = uifigure;
btn = uibutton(fig, 'Text', 'Press');

This creates a slider in the window that goes from 0 to 100.

MATLAB

fig = uifigure;
slider = uislider(fig, 'Limits', [0 100]);

This adds a text label showing 'Hello!' in the window.

MATLAB

fig = uifigure;
label = uilabel(fig, 'Text', 'Hello!');

Sample Program

This program creates a window with a slider and two labels. When you move the slider, the number next to it updates to show the current value.

MATLAB

function simpleUI
    fig = uifigure('Name', 'Simple UI');
    lbl = uilabel(fig, 'Position', [100 150 100 22], 'Text', 'Move the slider');
    sld = uislider(fig, 'Position', [100 100 150 3], 'Limits', [0 50]);
    valLabel = uilabel(fig, 'Position', [260 90 50 22], 'Text', '0');

    sld.ValueChangedFcn = @(src, event) updateLabel(src, valLabel);
end

function updateLabel(slider, label)
    label.Text = num2str(slider.Value);
end

Important Notes

UI components need a uifigure window to appear.

You can connect actions like button clicks or slider moves to functions using callbacks.

Positions are given as [left bottom width height] in pixels inside the window.

Summary

UI components let you build interactive windows in MATLAB.

Use uifigure to create the window, then add buttons, sliders, and labels.

Callbacks let your UI respond when users interact with components.

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