MIT App Inventor Exam Guide

MIT App Inventor Exam Guide

• WebViewer Component: Displays web content in an app
  • Loads a website using WebViewer.GoToUrl("https://www.example.com")
  • Can be used with buttons to open webpages on click

Event Handlers

• User-Initiated Events: Triggered by user actions, like button clicks

  • Example: Changing label text on button click: Button1.Click → Label1.Text = "Hello, World!"

• Sensor Events: Triggered by device sensors (e.g., accelerometer)

  • Example: Resetting app on shaking: When AccelerometerSensor.Shaking → ResetAllValues()

• Automated Events: Triggered automatically, like timers

  • Example: Incrementing label value every second: Clock1.Timer → Label1.Text = Label1.Text + 1

Properties

• Description: Define the appearance and behavior of components
  • Example: Set button text: Button1.Text = "Click Me!"
  • Example: Set background color: Screen1.BackgroundColor = Color.Red

Data Types

• Numbers: Used for calculations

  • Example: Result = Number1 + Number2

• Strings: Alphanumeric data

  • Example: FullName = "John" + " " + "Doe"

• Booleans: True or False values

  • Example: Check if positive: If Number > 0 → BooleanValue = True

Variables

• Description: Data storage that changes during app execution
  • Example: Store a score: Score = 0
  • Example: Update a variable: Score = Score + 10
  • Naming rules: Use underscores (e.g., user_name)

Arithmetic Operators

• + / - / × / ÷: Standard mathematical operations
  • Modulus (%): Returns the remainder
    • Example: Check for even number: If Number % 2 = 0 → Label.Text = "Even"

Logical Operators

• && (AND): True if both conditions are true

  • Example: Check if both inputs are positive: If Number1 > 0 && Number2 > 0 → Label.Text = "Both Positive"

• || (OR): True if at least one condition is true

• ! (NOT): Reverses a condition

  • Example: Toggle a condition: BooleanValue = !BooleanValue

Blocks Overview

• Text Blocks: String manipulation

  • Example Result = Text.ToUpperCase("hello")

• Math Blocks: Calculations

  • Example: Result = Math.Sqrt(Number)

• Data Blocks: Data storage and retrieval

  • Example: Item = List.GetItem(3)

• Logic Blocks: True/false conditions

  • Example: If Number > 10 → Label.Text = "Greater than 10"

Assignment Operators

• =: Assign a value.
• +=: Increment a value.
• -=: Decrement a value.
• *=: Multiply a value.
• /=: Divide a value.
  • Example: Increase score: Score += 5
  • Example: Halve a value: Value /= 2

Conditional Statements

• If-Else: Executes code based on a condition
  • Example: Check age eligibility: If Age >= 18 → Label.Text = "Eligible" Else → Label.Text = "Not Eligible"

Loops

• For Loop: Repeat a block a set number of times

  • Example: Display numbers 1 to 5: For Each Number From 1 To 5 → Label.Text = Number

• While Loop: Repeat while a condition is true

  • Example: Keep adding 1 until a number is 10: While Number < 10 → Number += 1

Lists

• Description: Collections of items
  • Example: Create a list: MyList = ["Apple", "Banana", "Cherry"]
  • Example: Add item: List.AddItem("Date")
  • Example: Remove item: List.RemoveItem(1)

Procedures/Functions

• Description: Reusable code blocks
  • Example: Define a procedure to calculate area: Procedure CalculateArea → Area = Length × Width
  • Example: Calling the procedure: CalculateArea(5, 10)

User Interface Components

• Examples: Buttons, Labels, TextBoxes, Layouts (e.g., Vertical Arrangement) 

Sensors

• Examples:
  • Accelerometer Sensor: Detects motion (e.g., When AccelerometerSensor.Shaking → ResetGame())
  • Location Sensor: Gets GPS coordinates (e.g., Latitude = LocationSensor.Latitude)

Database Integration

• TinyDB: Local data storage

  • Example: Save user score: TinyDB.StoreValue("Score", Score)

• FirebaseDB: Cloud data storage

Error Handling

• Examples: Check for null values: If Input = Null → ShowError("Invalid Input")

Test your knowledge of the MIT App Inventor with this comprehensive exam guide. It covers essential components like WebViewer, event handlers, properties, and data types. Perfect for anyone looking to enhance their app development skills.