Android App Development

As students create Android applications that performs specific functions, guided by the steps of the engineering engineering design process, they are doing just what software engineers do as they develop applications that we all encounter on a daily basis. This includes business software, communication software, compilers, computer graphics, and more. Ultimately, students must plan what the application will do, decide what it looks like, decide how to structure the software, test and edit to ensure the app works correctly. Thus, students act as software engineers in this hands-on application of the engineering design process.

After this activity, students should be able to:

• Design a mobile app for an Android device.
• Create a mobile app for an Android device using MIT's App Inventor.
• Apply the software/system (engineering) design process.

Students should have a basic understanding of computer programming design and control structure. Students should also have a basic knowledge of how MIT's App Inventor works. If this activity is conducted with students who have not previously worked with App Inventor, allow additional time for students to work through the MIT tutorials (http://appinventor.mit.edu/explore/learn.html) to gain an understanding of how App Inventor works.

In this activity, you will develop an app for an Android device. However, the activity is about more than the single app you develop. It is about the skills that you gain while you interact with the software that helps you develop your app. At the end of the activity, you should have the skills in place to write other apps for an Android device that use the internal sensors to collect data and store that data. If you desire, you can use the skills that you learn to write other apps for Android devices that can be published for public access and use.

Background

Students develop an app for an Android device that stores data collected during an experiment that can be used for analysis later. The Storing Android Accelerometer Data: App Design lesson has students complete online tutorials based on using MIT's App Inventor. At the end of this lesson, students should be prepared to write applications that can access an Android device's internal sensors.

The procedure is an outline and does not provide specific details on exactly what steps students must take to create their Android apps. This is because the purpose of this activity is for students to work through the process themselves. They might not figure out a code that works correctly the first time. This is an expected part of the learning process that forces students to evaluate their mistakes and redesign their codes. If too much information is provided, students never experience this critical part of the design process.

Before the Activity

• Install and set up the App Inventor software. Instructions for how to do this are provided in a tutorial on the MIT website: https://appinventor.mit.edu/explore/install-app-inventor-software.html
• The teacher and students should have a basic working knowledge of programming and how App Inventor works. Refer to MIT's tutorials for App Inventor at: http://appinventor.mit.edu/explore/  

With the Students

Part I:

Students plan a mobile android app that can access the accelerometer on an Android device. This planning consists of the first two steps in the software/system design process, namely the requirement analysis and design steps. When working through these steps, facilitate a lot of discussion about how the application should function. No actual code is written at this point; rather, students write pseudo-code.

Pseudo-code is a rough draft of written computer code. It is syntax independent; meaning the language being used is irrelevant, so the pseudo-code simply puts the blueprint or plan for all or part of a program into words that can next be translated into a specific programming language using that language's particular syntax. Refer to the attached Pseudo-code Example (PDF).

Writing pseudo-code is a computer programming method in which the designer determines what an application must do without writing any code in the programming language's syntax. It might take the form of a flow chart or block diagram. In each stage of the pseudo-code, students need to think about the ordering, control structures and algorithms that are necessary to accomplish that stage. Have students work in groups of 2-3 to each discuss and figure out a design that allows them to create code that directs an android device to store and recall data. During the discussion, encourage them to use markers and large sheets of paper or dry-erase boards. Once group comes consensus on how to build the code is achieved, have students draw detailed diagrams of the necessary App Inventor blocks to share with the class. The diagram should include labels, colors and the correct connection types.

Part II:

Students use MIT's App Inventor to create an application that stores the accelerometer data from an Android device. This part of the activity is the implementation, testing and evolution phases of the software/system design process. Students create the software code using App Inventor (implementation), test to see if the code functions, and look for possible improvements (evolution). The program they create also allows students to retrieve the data and manually transfer it for analysis using Microsoft Excel, Geogebra, or a similar programs.

Follow this general process to create a program within App Inventor. Encourage students to add or modify these basics in order to make the program user-friendly. These steps are provided only as a guideline to help facilitate the implementation phase.

1. Create a new application titled "AccelerometerData."
2. The program needs a clock (the clock should not be enabled; wait until the start button is clicked to enable the clock), labels for displaying the data, start, stop and submit buttons, a TinyDB, and an AccelerometerSensor. Drag these in from the Palette.
3. Open the Blocks Editor.
4. In the Blocks Editor, the program needs the following:

• A variable to keep track of the timer
• A StartButton. Click that resets and enables the timer
• A Clock1.Timer thT increments the timer by one, sets the acceleration text box to the chosen value of the accelerometer sensor (x, y or z), and stores that value in the TinyDB, using the timer value as the tag
• A StopButton.Click that disables the timer and clears any text boxes
• A SubmitButton.Click that sets the text of the acceleration text box to the value from the TinyDB using the number typed into the timer text box as the tagThe App Inventor user interface.CopyrightCopyright 2010 Pùnsa, Wikimedia Commons: http://commons.wikimedia.org/wiki/File:Interf%C3%ADcie_App_Inventor.png

Pre-Activity Assessment

Review the software/system (engineering) design process with students and how it can be applied to this type of activity. Ask students to list each step in the process and write an example of what they might do during each step. Ask students to share their response with the class. (Details on the steps of the engineering design process and the software development life cycle may be found in the Background section of the associated lesson.

Activity Embedded Assessment

Circulate around the room while students are designing (writing pseudo-code) to assess their progress. Later, when the designs are implemented, be available to assess progress and assist with implementation.

For the teacher's use, refer to screenshots of example App Inventor Code for this program in the App Inventor Code for Accelerometer Activity (PDF), and the Android App developed in App Inventor is provided in Accelerometer Android App (ZIP). Use these files as an answer key or teacher guide.

Post-Activity Assessment

Have students complete the following performance assessment: Create an application that stores your GPS locations over a given time interval.

This code looks similar to the acceleration application, but requires a "Location Sensor" from App Inventor instead of an "Accelerometer Sensor." To grade this challenge, look at the design elements that students created as well as the code. The ultimate test of the program is to run the developed Android app and see if it indeed stores GPS locations over a time interval. Base part of the assessment on how students applied the software/systems design (engineering) process in the completion of the mobile app.

For the teacher's use, example screenshots of the GPS Location Storing App created in App Inventor are provided in App Inventor Code for GPS Location (PDF), and the Android App for storing GPS data is provided in GPS Location Android App (ZIP).

Assign students to complete one of the following writing assessments. Answers are provided in the attached file: Android App Design Assessment Solutions (PDF).

• Describe the purpose of the TinyDB when creating an Android app.
• Create a button that toggles off and on in an Android app. Explain what steps you would have to include in App Inventor to create this button and draw some pseudo-code that represents the programming of the button.

Have students create other mobile apps of their choosing to solve a problem or challenge decided by the teacher or the class.