HelloPurr: Build, Conceptualize, Customize


Build It

  1. Open a browser and navigate to http://beta.appinventor.mit.edu. Login with your Google account.
  2. Now build your first app, HelloPurr. Follow the instructions in App Inventor chapter 1, using either the paperback version, the pdf version, or the step-by-step video lesson. You can find your own kitty picture and meow sound on the web, or use the ones at: http://examples.oreilly.com/0636920016632/

Conceptualize It

After completing the Hello Purr tutorial, discuss these questions with a partner or small group, jotting down notes while you discuss. Later, create a portfolio page with answers to the questions in your own words. Topics: Events, event-handlers, components, properties, function calls, parameters, testing and deploying an app.

  1. App Inventor has two main windows. What are they and what do you do with them?
  2. Testing and Running an App
    • a. How do you test an app while you're developing it?
    • b. How can you download an app you build to your phone?
    • c. What if you didn't have a phone, but wanted to program some apps. Could you? How?
  3. For the HelloPurr app, name the:
    • visual components:
    • non-visual components:
    • properties:
    • events:
    • event-handlers:
    • function calls:
  4. There are no Image components in the app, yet a picture appears. Explain.
  5. One function call in the HelloPurr app requires an argument (also known as parameter). Which function is it and what is the parameter?

Customize It

  1. As you shake the phone, the meows will sound strange, as if they are echoing. That is because the accelerometer sensor is triggering the shaking event many times a second, so the meows are overlapping. If you look at the Sound component in the Designer, you will see a property called Minimum interval. That determines how close together successive sounds can start. It is currently set at a half-second (500 milliseconds), which is less than the duration of a single meow. By playing with the minimum interval, you can change how much the meows overlap.
  2. If you run the packaged app and walk around with the phone in your pocket, your phone will meow every time you move suddenly, something you might find embarrassing. Android apps are typically designed to keep running even when you are not looking at them; your app continues to communicate with the accelerometer and the meow just keeps going. To really quit the app, press the menu button and choose close application.