General

An Update on the Tip Calculator App, and How to share on social media

I have added buttons after each post on the App Inventor Tutorial so you can quickly share these posts on Facebook, Twitter, Google+ and so on. Please feel free to share! Your friends might like to know how they can create their own Android apps too (unless they are stuck using an iPhone … oh dear!)

An Update on the Tip Calculator App

I said there would be 3 versions and I was going to publish version 3 this evening … but we ate at a restaurant tonight and I used version 3 to calculate the tip and promptly thought of improvements!

So this evening I rewrote Version 3 (whose tutorial will appear shortly) and then created two more versions!

  • Version 3 will introduce a refined user interface that eliminates user data entry errors completely.
  • Version 4 introduces “procedures” to clean up the code in preparation for version 5 and introduces the concept of “refactoring” where we rewrite the code to make it better.
  • Version 5 revises Version 4 to make the calculation of the tip fully automatic.

So scratch those previous references to three Tip Calculator versions – we are going for five!

Tips

Tip: Copy and Paste within the App Inventor Block Editor

This is not obvious but … you can select a group of blocks and press Ctrl-C (on Windows) and then press Ctrl-V (on Windows) to copy and paste your blocks.

Press Ctrl-X (on Windows) to delete  a selected group of blocks.  If you did not mean to delete those blocks, press Ctrl-V and paste them back!

Another trick is to select a block or blocks and then press right-click on your mouse (or Ctrl-click on Mac OS X) and then select Duplicate from the popup menu. Copy and paste should also work on Mac OS X using the standard Mac OS X keystrokes but I have not yet tested it there.

 

Components, User Interface/Design

Tip Calculator App (version 2) for App Inventor

What the App Does

This is a simple app to calculate the tip and total bill at a restaurant – or other service provider where a tip is common place.

This is the second of 3 apps that implement a tip calculator.

  • Version 1 introduced the basic app and the use of error checking to handle user data entry mistakes.
  • Version 2 (this tutorial) introduces the Slider user interface component to select the tip amount. Using the Slider, the user selects a tip from 0% to 30%. Since there is no text entry, it is not possible for an incorrect tip value to be entered.
  • Version 3 will introduce a way to avoid all user data entry errors – by designing the app in such a way that the user can enter only correct values.

The Tip Calculator User Interface

In version 2, we eliminate the text box for tip percentage and replace it with a Slider component and we use a Label component to display the current setting of the Slider. A slider is something you drag with your finger, as shown in this screen shot:

Screenshot_2014-11-05-12-31-57

We set the tip amount by putting our finger on the “thumb” and dragging the thumb left or right. “Thumb” is the name given to the moveable control that appears on the slider.

As we drag the “thumb” control on the slider, the amount of the selected tip is shown – which is 20% in this screen shot.  Using this design with a Slider, it is impossible for someone to enter an invalid tip!

Continue reading Tip Calculator App (version 2) for App Inventor →

App Inventor News

Lenovo and NAF sponsor App Inventor-based STEM curriculum

Students will be using App Inventor:

Lenovo and the National Academy Foundation (NAF) today announced 10 NAF Academies have been selected to participate in the Lenovo Scholar Network, a program designed to enable the next generation of developers and entrepreneurs through a rich application development curriculum and creation of apps. As part of the program, students will participate in a project-based competition that tasks them with designing and developing a mobile app and a business plan for taking the app to market.

via Lenovo and the National Academy Foundation Announce Academies Selected to the Lenovo Scholar Network | Business Wire.

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