Category Archives: Components

Components, Programming Method

Example of the new App Inventor “Responsive Design” Feature

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MIT App Inventor introduced today their new “responsive design” features so that apps can work “better” on different sized screens. Using these new features, you can create a single app that should run on both a smart phone and a tablet, yet still display proportional user interface controls. Prior to this, your nicely designed smart phone app could end up having very small buttons or text boxes when run on a tablet; now, these components will resize as needed.

The name “responsive” comes from the ability of the app to “respond” to the size of the device and to change the size of controls so they maintain a similar size on each device. The terminology “responsive web design” also refers to web sites that are designed to work with different sized mobile device screens – here is a link to a great article about responsive web site design, passed to us by reader David – thanks!

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App Inventor News, Components, Documentation

App Inventor to add “Responsive Design” features next week

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MIT App Inventor upgrade coming next Monday – the upgrade will support apps running on devices with different size screens, such as a smart phone versus a tablet.

There’s one important rule when using App Inventor to create apps with responsive design:

Specify widths and heights of components as percentages of the screen width and height, rather than as fixed numbers of pixels.

For example, to make a button whose width is half the screen width, set the button’s width to be 50 percent rather than setting it to a specific number of pixels.

See Responsive Design in App Inventor

Please see the link for details on this upcoming change.

Apps written in Java and the Android SDK have access to additional methods of creating flexible design layouts, or even multiple layouts, for different screen sizes.

App Inventor News, Components

MIT begins testing “App Inventor Extension Components”

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MIT has begun testing a new App Inventor feature that will enable developers to create their own “extension components”. Extension components are written in Java. Once created and tested, these new components may be shared with other App Inventor developers for use in programs.

What this means: if App Inventor lacks a feature or capability, then a Java developer familiar with App Inventor and its components software development kit will be able to add new features to App Inventor. Over time, the capabilities and power of App Inventor are likely to grow enormously – and rapidly. The ability to extend App Inventor’s features/components is an exciting and tremendously important development for the future of App Inventor!

For now, this feature is in “test mode”.

Source: App Inventor Extension Components available for testing | Explore MIT App Inventor

Components, General

App Inventor Stores Numbers as “Floating Point” Format

When you type a number, such as “123”, computers convert the text values of “123” into an internal representation used by the computer. There are many possible ways that numbers can be represented inside a computer. For example, the computer could:

  • keep numbers in their original text format “123” (decimal format)
  • convert them into a binary representation (binary integers)
  • a “floating point” representation (floating point or “float” format)
  • or even a “binary coded decimal” (BCD) representation.

Each internal format has benefits and drawbacks, depending on the application. Most computers (and programming systems) convert entered numbers from their original text format into either integer format or floating-point number format.

App Inventor converts values to floating point format. Which is fine, except that you will encounter some odd and subtle issues. As the link below notes, in App Inventor arithmetic, 0.3 + 0.6 does not equal 0.9!

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App Inventor News, Components

New App Inventor 2 “Companion” app released today; new features

Changes between nb143i and nb144 (June 30, 2015)

  • When a component is renamed in the designer, any related collapsed blocks will be properly renamed now.
  • Screen1 now has properties that permit you to hide both the top “Status” and “Title” Bars
  • The selected item in a ListView is now highlighted
  • Activity Starter component now has a “Activity Canceled” event
  • Fix to the Player Component so it doesn’t spontaneously start playing after a phone call or other interruption
  • Bugfix to Image Sprite rotation which had left screen artifacts on some devices
  • Add Math blocks to convert between decimal, Hexidecimal and Binary representation
  • Clock Component now permits you to format a date or time arbitrarily. You provide a “format string”
  • You can now have both a Background Image and a Background Color and the “right thing” happens
  • TextToSpeech: The designer now uses dropdown menus to select Country and Language. Added blocks to fetch the supports countries and languages on a given device

Source: Release Notes for MIT App Inventor 2 (Beta)

Components, Programming Method, Tips

Can you make a video player in App Inventor? Not really, unfortunately.

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A question from a reader: Can we make a video player in App Inventor?

The short answer is, unfortunately, not really.

In the App Inventor Designer, in the Palette’s Media section, you can drag a Video Player into the viewer. But this Video Player only plays video files (WMV, MP4) that are stored inside your app (not on the web) and these files are limited to just 1 megabyte in size. Therefore, the Video Player feature in App Inventor is so limited as to not be very useful for most applications.