Tag Archives: programming

App Inventor 2 Tutorial Volume 2 is now available at Amazon

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Volume 2 of the App Inventor 2 Tutorial is now available at Amazon as an e-book via this link: App Inventor 2 Tutorial Volume 2: Step-by-step: Advanced features including TinyDB.  The e-book will also be available from Google Play shortly.

Description

MIT App Inventor 2 is a fast and simple way to create custom Android apps for smart phones or tablets. Volume 2 in the series introduces debugging methods, explains additional controls not covered in Volume 1, introduces “agile” methods for developing a real world app, and provides sample code for using the TinyDB database.

The App Inventor 2 Tutorial series is targeted at adult learners (high school and up). App Inventor 2 provides a simplified “drag and drop” interface to layout your app’s screen design. Then implement the app’s behavior with “drag and drop” programming blocks to quickly assemble a program in a graphical interface.

Volume 1 of this series covered the basics of the App Inventor user interface Designer and the Blocks programming editor, plus basic “blocks” programming concepts and tools for arithmetic, text processing, event handling, lists and other features. Volume 2 builds upon Volume 1 to provide tips on debugging programs when the apps work incorrectly, how to use hidden editing features, and how to install your own apps on to your phone or tablet for general use. Code samples are provided for using the Notifier component for general use or for debugging, for user interface control tricks such as buttons that change color continuously or implementing the missing “radio buttons” component, using ListPicker and Spinner for list selections, and using the WebViewer to display web pages in your app. The book includes a large section on designing and building a sample real world application and finishes with a chapter on using the TinyDB database.

For readers of the blog, Chapters 4–8 are based on the tutorial already presented here. Chapter 2 and Chapter 9 on TinyDB are all new material.

Chapters

  • Introduction
  • Chapter 1 – App Inventor Tips
  • Chapter 2 – Debugging App Inventor Programs
  • Chapter 3 – User Interface Control Tricks
  • Chapter 4 – Designing and Building a Real World Application
  • Chapter 5 – Tip Calculator Version 2
  • Chapter 6 – Tip Calculator Version 3
  • Chapter 7 – Tip Calculator Version 4
  • Chapter 8 – Tip Calculator Version 5
  • Chapter 9 – Using the TinyDB database

(Volume 3 is now available – App Inventor 2 Databases and Files adds substantially more information on TinyDB, plus TinyWebDB and Fusion Tables and includes the full introduction to TinyDB).

AppInventor_Volume2Cover

“Visual Development” system for Arduino

As you know, MIT App Inventor is a graphical-based programming system, or a “visual development” system where programs are constructed by dragging and dropping “blocks” onto a Blocks editor.

Arduino, which we mentioned in conjunction with our Bluetooth interface code, is a microcontroller system that is normally programmed in a language similar to the C++ programming language – which is text-based.

Mitov Softwware has introduced a new visual programming system for Arduino. I have not yet had a chance to try this out – the software is in “Beta” test phase and is not yet generally available.

The simplicity of an App Inventor type programming environment might then be available for Arduino applications. This is very exciting. It may be helpful for enabling more kinds of people, with different types of backgrounds than software developers(!) to write code for Arduino boards.

Program Arduino boards visually, fast and easy with Visuino #Visuino #Arduino

Source: Visuino – Visual Development for Arduino by Mitov Software

I have used this screen shot from their web site to illustrate the general idea – really looking forward to trying this out!

screenshot-03

App Inventor Classic (version 1) to Shut Down on July 15 

Most users are already using AI 2 and are unaffected by this change. But if you are still using AI Classic (version 1), then this message is very important – please click through the link to read the full story!

May 24, 2015 — MIT App Inventor Classic will shut down on July 15, 2015. After July 15, 2015, you will not be able to access or edit your existing AI Classic projects. It will be impossible to create new AI Classic projects.This shutdown applies only to AI Classic (AI1). App Inventor 2 (AI2) will not be affected.

MIT will not automatically convert your AI1 projects to AI2 projects. But MIT will provide a conversion tool that will help you convert the AI projects that are important to you into AI2 projects. We expect to release this converter in about 2 weeks (i.e., around June 8).

Source: App Inventor Classic to Shut Down on July 15 | Explore MIT App Inventor

How do you know which version you are using?
Login to App Inventor and create or open a project. If the URL address in your browser begins with
http://ai2.appinventor.mit.edu/

then you are using Version 2.

Displaying web pages in your Android apps

Last year, I presented a short tutorial on displaying web pages from inside your App Inventor apps. Now, here is a some what improved version that prompts for a web address URL, checks to see if http:// has been entered, and if not, prepends http:// to the front of the address. Then the web page is displayed.

The Designer View

There is not much to the user interface – a text box to enter the web URL and a button to display the web page. The page then appears below the button, and the content may be scrolled on the screen.

To create this user interface, drag a horizontal layout onto the screen and then add a label for the “Web page URL” prompt, followed by a text box for the data entry. Then add the Display web page button.

From the User Interface section of the Palette, at the left of the Designer screen, drag and drop a WebViewer component on to the design area.

Screenshot_2015-02-10-15-15-17

 

The WebViewer is not a full Internet browser – it is a component that displays the specified web page only. The WebViewer does not support standard browser features, such as saving web page content nor does it provide a history of the web pages visited.

The Blocks Code

Continue reading Displaying web pages in your Android apps

Part 2: Sending numeric data using App Inventor Bluetooth communications

Part 1 of this tutorial introduced Bluetooth communications and implemented a simple method of sending text data back and forth between two Android devices over the Bluetooth wireless link. If you are not familiar with using App Inventor’s Bluetooth component, start with Part 1.

In Part 2, a data packet concept is introduced to guide the communications between devices, and is used to send a combination of text and numeric data. This section introduces the concept of binary numbers so that you can understand why we would handle text and numbers in different ways.

This tutorial modifies the user interface of both the client and server programs introduced in Part 1. Then, blocks code is added to send text and numeric data. Numeric data is sent as binary data using special methods of the Bluetooth components.

Related:

Related:

Continue reading Part 2: Sending numeric data using App Inventor Bluetooth communications

Positive comments about MIT App Inventor from i-Programmer

App Inventor is an amazing way to create Android applications. You don’t need to be able to program to use it, but if you can then all the better.

All I can say is that as a programmer this is the first time in quite a while that a development environment and its associated “language” has brought a smile to my face. It’s not perfect, but if you give it a little room to grown on you might just smile as well.

Although App Inventor is sometime described as an educational toy that you can use to get kids interested in programming, don’t let this fool you into thinking that you can’t do real things with it. It makes a very good prototyping facility and a couple of the prototypes that I have created have actually ended up as final apps that are still in use.

via Getting started with MIT App Inventor 2.

I have the same thoughts about App Inventor too. App Inventor is much bigger than a tool for teaching programming.

Blocks Editing Tip: Arranging and collapsing blocks in the editor

As you develop your App Inventor program using the Blocks editor, do you find your blocks overlapping and crashing in to one another on the screen? You know, like this:

AIBlockMess

You can drag the blocks on the screen so they no longer overlap, but dragging each block is tedious (time consuming). But there is an easy way to automatically re-arrange the blocks.

  • Move the mouse pointer to any part of the white space outside the blocks
  • On Windows, right-click the mouse button
  • On Mac OS X, press Ctrl and click the mouse button

Continue reading Blocks Editing Tip: Arranging and collapsing blocks in the editor

Using TinyDB in App Inventor

(This post was completely rewritten and updated on October 30, 2015)

What is TinyDB?

TinyDB is a simple “database” that stores data on your phone or tablet. Unlike program variables that go away when your app is finished running or your phone is re-set, values stored in TinyDB remain on your phone for use the next time your app is run.

About Memory on your Phone or Tablet

Your smart phone or tablet typically has two primary types of memory: RAM and FLASH memory.

RAM stands for “random access memory” – but today we mostly think of RAM as memory that can be accessed very fast (as compared to Flash or hard drive memory storage). RAM retains values as long as power is applied to the RAM circuity. Once we turn off the power, the values stored in RAM are lost. (In some applications, extra batteries are used to continuously provide power to RAM even when the “normal” power is turned off.)

Flash memory retains values when the power is turned off. But access to Flash RAM is not as fast as access to conventional RAM memory.

Why is it called “Flash”?  There was an early version of memory technology where the memory was erased by literally flashing it with ultraviolet light. However the inventor of Flash RAM chose the name “Flash” for different reasons. Modern Flash RAM is read, written and erased electronically.

App Inventor variables are stored in RAM memory – and the content of RAM is erased or reset whenever the power is turned off. TinyDB, on the other hand, stores values in FLASH RAM, where the values remain even when the power is turned off.

Using TinyDB

TinyDB provides a simple way to store and retrieve data efficiently and to store the data in long-term storage.  TinyDB is based on the concept of a “tag” to identify the stored data, and the data value. Think of a “tag” as like using your name as your identification to look up your address:

Tag value: Martin

Value: 123 Main St, Anytown, USA

or

Tag value: Alexa

Value: 321 Other St, Someplace, USA

TinyDB uses the “tag” (such as Alexa) to quickly locate the corresponding value. Even if you have 100 names and addresses stored in TinyDB, TinyDB can  look up the “tag” quickly and use the tag to find the corresponding value. We do not need to know how TinyDB does its look up so fast – it just does it [see Footnote 1].

In most database programs, the “tag” is known as a “key” or “key value”. App Inventor uses the name “tag” in place of “key”. As I am used to the name “key”, I tend to use “key” were I should have used “tag” in App Inventor! You will see this is the sample program, below!

To learn how to put TinyDB in operation, we construct a very simple app, described below.

Continue reading Using TinyDB in App Inventor