Android phones and tablets support Bluetooth communications (“BT”).

BT is a very low power, very short range communication technology used for connecting earphone and headphone adapters, wireless microphones, and wireless keyboards and mice to computers and tablets.

App Inventor supports BT links and can be used to transmit data back and forth between two Android devices.

When two devices communicate, one device acts as a “server” and the other as a “client”, although either send and receive data.

I now have basic Bluetooth communication working between two Android phones. As I finalize the Bluetooth sample app, I will post a tutorial here on how to set up Bluetooth and how to write apps that use Bluetooth communication.

Longer term, I intend to connect an App Inventor app to an Arduino microcontroller board using the Bluetooth link. I will post information on that once it is available.

(Due to volunteering every evening with a FIRST Robotics team, and a few extra things going on, my updates are a little less frequent at the moment – sorry!)

This post is a major update to a previous post on reading and writing text files using App Inventor. This revision includes information on how to locate the text files you create in your App Inventor apps, plus how to transfer those files from your smart phone or tablet to your computer.

An earlier blog post described how to store data using TinyDB so that an app’s data can persist between uses of the program, or even to share data between screens in a program.

Another way to save data is to write the data to a file on your Android device. App Inventor has introduced a File control that lets us write text data to a file and then read it back, later. As we will see, the File control is not the easiest thing to use but with some work, the control can be used to store data from our program into a file.

Once data is in a file, you could, hypothetically, transfer the file from an Android to device to another computer. Because Android stores the files in a way that they may not be readily accessible – or even visible – we need to use some simple tricks to find the file and transfer the file to a computer.

Update: To learn more about text files and transferring data in the CSV file format, check out Volume 3 of “App Inventor 2 Databases and Files” – thanks!

Continue reading Updated: Writing and Reading Text Files Using App Inventor →

How to implement a button that continuously changes color, as demonstrated in this video example:

The Designer View

Create a simple user interface with two buttons – one to start the color change and the other to stop the color changes. In the button properties, set the button shape to “oval”.

Drag a clock component into the Designer – the Clock will appear as a non-visible component at the bottom of the Viewer.

Blocks Code

Continue reading Changing an App Inventor button’s color continuously →

This tutorial covers the simple changing of the color of a button, while the app is running. You may also set a component’s color by changing the color properties on the Properties list in the Designer.

A second tutorial will show how to implement the continuously changing color demonstrated in the video example. That will be posted next!

The Designer View

To demonstrate the “simple” version, create an app with this user interface:

That’s simple!

Each time the button is pressed, the color of the button will change.

Blocks Code

Continue reading Changing the color of a button (or other components) in App Inventor →