MIT App Inventor Update

An update to MIT App Inventor was pushed out on 16 June, and users will see a pop-up screen alerting them to this on their first sign-in after that date. None of the updates described in the release notes should have an impact on existing Smart Skills apps. The new Pedometer component may be of interest for the development of exercise and fitness apps.

If you have installed the AI2 Companion App on an Android device in order to use the WiFi or USB 'live debug' methods, it will need to be updated to use the new features in this App Inventor release. If you installed the Companion App from the Google Play store, it will update automatically; if you installed it directly to your device, you will need to manually update to version 2.37 at appinv.us/companion.

Nox App Player

We are investigating Nox App Player as an alternative to ARC Welder for PC-based testing of apps built with App Inventor. Nox is an Android 4.4.2 emulator, allowing Android apps to be run on a PC.

The installer is just over 250MB and can be downloaded from http://en.bignox.com/. Installation requires Administrator privileges, and an email address is requested though appears not to be used. Installation and startup is a little slow. Nox recommends that virtualisation (VT-x) is enabled in the computer BIOS to improve performance, but this is not required and the emulator performs well without it.

To test an app with Nox, build and save the APK file in App Inventor as usual. The APK file can be dragged and dropped onto the Nox emulator, or there is a Load APK button in the vertical control panel to the right of the emulator. Once installed, apps are retained in the emulator until manually deleted. Switching between landscape and portrait orientation requires Nox to be restarted.

BlueStacks App Player

We are investigating BlueStacks App Player as an alternative to ARC Welder for PC-based testing of apps built with App Inventor. BlueStacks is primarily intended as a games platform, allowing Android games to be played on a PC or Mac and streamed live if desired.

The installer is just over 300MB and can be downloaded from http://bluestacks.com/. Installation requires Administrator privileges. Some apps are installed automatically, though most of the apps shown in the channels are links to the App Store. * There is no need to connect a Google account in order to test APKs, so the One Time Setup tab can be closed. ** The BlueStacks TV window opens every time BlueStacks is started; it can be closed or ignored.

To test an app with BlueStacks, build and save the APK file in App Inventor as usual. Double-click the APK file to install it in BlueStacks, or click the APK icon in the control panel and select the file. (If your browser is configured to open a dialog box for downloads, APKs can be installed directly to BlueStacks without saving them first). Installed apps appear on the Android tab; click on All Apps in the Recently Played section to see newly installed apps. Apps can be switched between landscape and portrait by clicking the rotate icon at the top of the control panel. Usually this will close and restart the app in the new orientation, though it may need to be manually restarted. To overcome this, the ScreenOrientation property of Screen1 in App Inventor should be set to Portrait when creating the app.

BlueStacks includes a browser app; it is therefore possible to use App Inventor within BlueStacks, though the emulated screen resolution of 1280x720 is not ideal, and it may not be as responsive as a native browser. Build and download the APK as normal, then 'swipe' down with the mouse on the download notification indicator to install.

Online reviews indicate that the free version of BlueStack may install additional apps automatically from time to time. A thorough review of the licensing terms has not been conducted at this point.

* Update, 8th September 2016:
The latest version of BlueStacks (2.4.44) requires the user to log in to Google during the initial setup. This was previously optional, with a One Time Setup screen being displayed from time to time: that screen is now gone, as is the Welcome screen, with the result that the new setup procedure is more predictable and the overall user experience is cleaner. Performance and stability have also been improved steadily over the last few months.

* Update, 23rd June 2017:
The latest version of BlueStacks (2.7.320) has a more conventional tablet-like appearance than earlier versions, and BlueStacks TV is no longer automatically launched on startup.

Note: The Google account is not logged out when BlueStacks is closed, so users should consider manually disconnecting their Google account when using BlueStacks on a shared machine: go to Settings - Accounts - Google and select Remove account from the dropdown menu in the top right. Alternatively, a school may choose to create a dedicated Google account for use with BlueStacks, and leave that account logged into all instances of BlueStacks. Students would still use their individual Google accounts with App Inventor.

Coding: Best Practices

It is important when writing software, in any language, that attention should be paid not only to the correct functioning of the code, but also to how the code is written and organised. Well written code is easier to understand, debug, maintain, enhance, and test. This can make or break a team software development project, and great emphasis is placed on adherence to coding standards and best practices in software design. It is equally important for solo developers who share their code with an Open Source community, or even when returning to one’s own code written some time in the past.

This document contains some guidelines which may be useful when programming with App Inventor, and which represent practical implementations of widely accepted programming principles.

Web Quiz App

A new app has been added to the UniTY section of the App Library. WebQuiz is a picture quiz similar to the quizzes in the APPlied and Smart Skills sections of the library, but using the Web Connectivity component of App Inventor to dynamically retrieve the images and answers from a web server. Only the minimum functionality to retrieve files from a web server is implemented: error handling and cache control have been omitted in the interest of clarity, but would be necessary for a production app. The sample files were uploaded to the web server via FTP, though creation of a web application to create and administer quizzes would be an interesting project in its own right.

ARC Welder Problems

If you are using ARC Welder to test apps, the latest update (24th March) appears to have caused problems for some users. In some cases, when downloading and installing ARC Welder, the first part completes (download of ARC Runtime) but the second part (download of ARC Welder itself) fails with a "Manifest Invalid" message. In some cases, the download and installation completes normally, but when an APK is loaded into ARC Welder, it crashes with the 'broken plugin' black screen. At this point we have not been able to confirm if these are widespread experiences, or whether a new release is planned to address them.

The workaround that we are using is to install Chrome Portable and use it instead of the normal Chrome browser. Chrome Portable runs the current version of Google Chrome from a self-contained folder, rather than integrating with the OS in the way that a normal installation does. There is no need to uninstall Google Chrome in order to install Chrome Portable. Download it from the green Sourceforge link on this page: http://portableapps.com/apps/internet/google_chrome_portable and run the executable to install. Tick the checkbox to run Chrome Portable after the installation completes. No shortcuts are created. Once this is installed, quit the standard Chrome browser, and continue as normal within Chrome Portable.

Amazon Fire tablet safety notice

Amazon have issued a recall for the power adapters supplied with Fire 7" tablets, and are asking customers to stop using the adapters. They are offering a free replacement service. Please follow the link below for more information.

https://www.amazon.co.uk/b?node=9730244031