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What MIT App Inventor Is and How It Works

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Imagine the student council at your school wants a simple phone app to announce the class meeting schedule. Building an Android app usually requires a programming language such as Java or Kotlin. With MIT App Inventor, you can build that app by snapping code blocks together, like solving a puzzle, right in your browser.

What is MIT App Inventor?

MIT App Inventor is a free tool made by the Massachusetts Institute of Technology (MIT) for creating Android apps. Your apps can also be tried on an iPhone through its companion app. You simply open ai2.appinventor.mit.edu and sign in with a Google account. There is no heavy program to install on your computer.

Two main workspaces

Every App Inventor project has two parts that you switch between with the buttons at the top right:

  • Designer: where you lay out the app's screen, such as buttons, text, images, and input boxes. It is like arranging the desks, whiteboard, and chairs in a classroom.
  • Blocks: where you build the app's logic or instructions. It is like the class rules: "when the bell rings, students enter the classroom".

How an app gets built

  1. You place components in the Designer, for example a Button and a Label.
  2. You set the components' properties, for example changing the button text to "See Schedule".
  3. In Blocks, you write the rule: when the button is pressed, change the label text to the class meeting schedule.
  4. You try the app live on your phone with the MIT AI2 Companion app. Every change appears immediately without reinstalling.
  5. When it is finished, you create an .apk file from the Build menu so the app can be installed and shared with friends.

Why is this approach good for beginners?

With code blocks, you cannot mistype a semicolon or a bracket, because blocks only snap together when their shapes fit. You can focus on what matters most in programming: thinking in order, making decisions, and storing data. These concepts are exactly the same ones professional programmers use, so later it is easy to continue to HTML, CSS, and JavaScript.

Remember: the Designer controls how the app looks, the Blocks control how the app works.

In the next lesson you will create an account, start your first project, and see it appear on your own phone.