App Designer basics in MATLAB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is MATLAB App Designer used for?

MATLAB App Designer is a tool to create interactive apps with a graphical user interface (GUI) without needing to write all the code manually.

beginner

Name two main parts of the App Designer interface.

The two main parts are the Design View where you drag and drop UI components, and the Code View where you write the app's behavior.

beginner

How do you add a button to your app in App Designer?

In Design View, drag a Button from the Component Library onto the app canvas.

beginner

What is a callback function in App Designer?

A callback function is a piece of code that runs automatically when a user interacts with a UI component, like clicking a button.

beginner

How do you run your app after designing it in App Designer?

Click the Run button (green triangle) at the top of the App Designer window to start your app and test it.

What view do you use to add buttons and sliders in App Designer?

A Editor

B Code View

C Command Window

D Design View

Design View is where you drag and drop UI components like buttons and sliders.

What happens when you click a button in an app with a callback function?

A Nothing happens

B The app closes

C The callback function runs

D The app restarts

Clicking a button triggers its callback function to run the code you wrote.

Where do you write the code that controls app behavior in App Designer?

A Code View

B Design View

C Command Window

D Help Browser

Code View is where you write the app's programming logic.

Which button do you press to test your app in App Designer?

A Run button (green triangle)

B Save button

C Stop button

D New button

The Run button starts your app so you can test it.

What is the main purpose of App Designer?

A To edit images

B To create interactive apps with GUIs

C To write scripts only

D To compile code

App Designer helps you build apps with graphical interfaces easily.

Explain the two main views in MATLAB App Designer and their purposes.

Think about where you design the look and where you write the code.

Describe what a callback function is and when it runs in an app created with App Designer.

It is code that responds to user actions.

Practice

1. What is the main purpose of uifigure in MATLAB App Designer?

easy

A. To add a button to the app

B. To create the main window for the app

C. To display text labels

D. To plot graphs automatically

Solution

1. Step 1: Understand the role of uifigure

   uifigure creates the main window or figure where the app components appear.

2. Step 2: Differentiate from other components

   Buttons and labels are added inside this window but are created with uibutton and uilabel.

3. Final Answer:

   To create the main window for the app -> Option B

4. Quick Check:

   Main window = uifigure [OK]

Hint: Remember: uifigure = app window [OK]

Common Mistakes:

• Confusing uifigure with uibutton or uilabel
• Thinking uifigure creates buttons or labels
• Assuming uifigure plots graphs automatically

2. Which of the following is the correct syntax to create a button in App Designer?

easy

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

B. btn = uibutton(uifigure, 'Click Me');

C. btn = uibutton('Text', 'Click Me');

D. btn = uibutton('Click Me');

Solution

1. Step 1: Recall uibutton syntax

   In App Designer, uibutton requires the parent figure as the first argument, then property name-value pairs.

2. Step 2: Check each option

   btn = uibutton(uifigure, 'Text', 'Click Me'); correctly uses uibutton(uifigure, 'Text', 'Click Me'). Others miss the parent or property name.

3. Final Answer:

   btn = uibutton(uifigure, 'Text', 'Click Me'); -> Option A

4. Quick Check:

   Button needs parent + 'Text' property [OK]

Hint: uibutton needs parent and 'Text' property [OK]

Common Mistakes:

• Omitting the parent figure argument
• Passing text without 'Text' property name
• Using wrong argument order

3. What will be the output when the following code runs in App Designer?

fig = uifigure;
lbl = uilabel(fig, 'Text', 'Hello');
lbl.Position = [100 100 100 22];

medium

A. No label appears because uilabel needs a callback

B. An error because Position is not a valid property

C. A label appears but text is empty

D. A label with text 'Hello' appears at position (100,100)

Solution

1. Step 1: Understand label creation

   The code creates a figure, then a label with text 'Hello' inside it.

2. Step 2: Position property sets label location

   Setting Position = [100 100 100 22] places the label at x=100, y=100 with width 100 and height 22.

3. Final Answer:

   A label with text 'Hello' appears at position (100,100) -> Option D

4. Quick Check:

   uilabel + Position sets label location [OK]

Hint: Position sets label location and size [OK]

Common Mistakes:

• Thinking Position is invalid property
• Assuming label text is empty by default
• Believing callback is needed to show label

4. Identify the error in this App Designer code snippet:

fig = uifigure;
btn = uibutton('Text', 'Press');
btn.Position = [50 50 100 30];

medium

A. Missing parent figure argument in uibutton

B. Position property cannot be set for buttons

C. Text property should be set after creating button

D. uifigure must be called after uibutton

Solution

1. Step 1: Check uibutton creation syntax

   uibutton requires the parent figure as the first argument to attach the button to the window.

2. Step 2: Identify missing parent

   The code calls uibutton('Text', 'Press') without specifying fig as parent, causing an error.

3. Final Answer:

   Missing parent figure argument in uibutton -> Option A

4. Quick Check:

   uibutton needs parent figure first [OK]

Hint: Always pass parent figure first to uibutton [OK]

Common Mistakes:

• Forgetting to specify parent figure
• Thinking Position can't be set for buttons
• Calling uifigure after uibutton

5. You want to create a button that changes a label's text to 'Clicked!' when pressed. Which code snippet correctly sets up the callback in App Designer?

hard

A. btn = uibutton(fig, 'Text', 'Press'); btn.Callback = @(btn,event) lbl.Text = 'Clicked!';

B. btn = uibutton(fig, 'Text', 'Press', ButtonPushedFcn, @(btn,event) lbl.Text = 'Clicked!');

C. btn = uibutton(fig, 'Text', 'Press'); btn.ButtonPushedFcn = @(btn,event) lbl.Text = 'Clicked!';

D. btn = uibutton(fig, 'Text', 'Press', 'Callback', @(btn,event) lbl.Text = 'Clicked!');

Solution

1. Step 1: Understand callback property name

   In App Designer, the button's callback is set using the ButtonPushedFcn property, usually assigned after creation.

2. Step 2: Check syntax correctness

   btn = uibutton(fig, 'Text', 'Press'); btn.ButtonPushedFcn = @(btn,event) lbl.Text = 'Clicked!'; correctly creates the button then assigns ButtonPushedFcn with an anonymous function to change label text.

3. Final Answer:

   btn = uibutton(fig, 'Text', 'Press'); btn.ButtonPushedFcn = @(btn,event) lbl.Text = 'Clicked!'; -> Option C

4. Quick Check:

   Set ButtonPushedFcn after button creation [OK]

Hint: Assign ButtonPushedFcn after creating button [OK]

Common Mistakes:

• Using 'Callback' instead of 'ButtonPushedFcn'
• Trying to set callback inside uibutton arguments
• Using wrong property names for callback