Using Firebase in a real app – “Here I AM!” GPS Demo app

A previous post introduced the experimental Firebase component in MIT App Inventor. Firebase is a cloud-based database that may be used by App Inventor apps, and which makes exchanging data between users easy. Note: Firebase is experimental and may change in the future. At the present time, there is one Firebase database that is shared by all users. See comments in previous post for more information.

This post uses the GPS location sensors in phones to determine the phone’s position in latitude and longitude. Pressing a button labeled “Send GPS” sends the latitude and longitude coordinates to another phone, which then draws the position on a map. In this way, two phone users can wander about and transmit their location to each other, sending the data through the Firebase cloud database. I named this app “Here I AM!” – pressing the Send GPS tells another user that “I am here!”

User Interface

To use this app, the exact same app should be running on two separate phones. You can run it on a single phone but obviously, you will not be getting updates from anyone else!

The first time you run this app on Android 6, you will be asked to give permission to use location information. Also, be sure to set Location services to on, in Android Settings.

As you move about, press the Send GPS button.  Your latitude and longitude will be sent to Firebase, the other app will be alerted to an updated location, and your location will be displayed on the Google maps on their phone. If they press Send GPS, then their location will be updated on your phone.

The Lat/Long. textbox displays either the latitude, longitude or is prefixed with “THEM:”. “THEM:” means the textbox is showing the other phone’s location; if “THEM:” is not shown, then the textbox is showing your own latitude, longitude.


Press Retrieve GPS to retrieve and display the latitude/longitude value currently stored in Firebase.

Press Show Map to display the  last retrieved location on the map.

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Some computer joke in this

Saw this sign at a campground, identifying 4 separate roadway loops where people may camp.

For programmers, this sign is amusing. “A Loop”, and “BCD Loops”. BCD stands for binary coded decimal, which is a way of storing decimal numbers for financial calculations. I know, bad joke – but one of those things that makes us software developers have a good laugh 🙂



MIT Professor Seymour Papert, passed away 31 July 2016

MIT Professor Seymour Papert was a forward looking visionary who pioneered the adoption of computing concepts in children’s education, including the development of Logo, Mindstorms and turtle programming. His distant work back in the 1960s and 1970s lay the foundation for today’s use of MIT App Inventor in children’s education. His contributions to education and computing are greatly appreciated.

Much more about Paupert’s background may be read in the NY Times or in this essay by a colleague here.

Demonstration app for using FirebaseDB in AppInventor

FirebaseDB provides for sharing between users all running the exact same app on their device. Read “What is FirebaseDB?” to learn more about FirebaseDB and what it does for your applications.

This is a quick and very short app that demonstrates the fundamental operation of FirebaseDB when used in MIT App Inventor. I hope to create a more interesting demo app a bit later.

Caution: FirebaseDB is an experimental component offered by MIT App Inventor. FirebaseDB remains under development and is subject to change; apps written today might not work in the future. Apps containing the FirebaseDB component will not work in the emulator – run on your phone or tablet instead. At this time, the cloud-based database is a shared database, shared among multiple users, and cannot – yet – be linked to your personal Google account.

FirebaseDB is Similar to TinyWebDB

The programming interface for FirebaseDB is nearly the same as that used for TinyWebDBTinyWebDB is a simple cloud-based database – to use, you need to set up the TinyWebDB on your own server or on Google’s servers. With your data stored in the “cloud”, your data may be shared among many apps. For the FirebaseDB demo, you do not need to set up your own server, nor do you need to use TinyWebDB:

For details on setting up and using TinyWebDB – including some tricks that enable sharing of TinyWebDB data between apps – please see my book,

  • App Inventor 2 Databases and Files (Volume 3 e-book)
    Step-by-step TinyDB, TinyWebDB, Fusion Tables and Files
    Buy from: Amazon, Google Books, Kobo Books

For more information, including a sample chapter, please see my App Inventor books page.

Sample App User Interface

Our simple demonstration app stores and retrieves a text value to and from the FirebaseDB. As with TinyDB or TinyWebDB, enter a “tag” value to use to look up the value. For example, a tag value could be a part number, and the value could be the text description of the part’s name. Or the tag could be a phone number and the value could be the name of the person who has that phone number.


The program is operated by entering a tag and a value and then pressing the Store Value button. The value entered is written to the FirebaseDB database in the cloud.

After a value has been stored, you retrieve values by entering the original tag and pressing Retrieve Value. The data corresponding to the tag is retrieved from FirebaseDB and display in the Value field, on screen.

If the app is run simultaneously on other devices, any data updates made on the other devices result in all devices receiving a data changed notification. When the data in the FirebaseDB is changed, the new data is displayed on all devices.

Designer View

A combination of vertical and horizontal layouts is used to organize the positions of the controls (see the Components list, below, or download the sample code).

Store Value and Retrieve Value are buttons. Tag and Value are labels, followed by text boxes for data entry.  Data Changed Event and the status message are both labels.

Drag the FirebaseDB component from the Experimental section of the Designer controls palette. You will receive a warning that FirebaseDB is experimental.



Blocks View

(Sorry for the image quality on these three blocks – the screen capture utility I used for these did not do a very good job)

The btnStoreValue event handler reads the enter tag and data value from the text boxes on screen, and then stores those to the FirebaseDB. Find the FirebaseDB StoreValue component by clicking on the FirebaseDB component in the Blocks list.


Fetching a store value is simple – call FirebaseDB’s GetValue method and pass to it the tag. Unlike TinyDB (but similar to TinyWebDB), the value is not read instantaneously but instead, once the data is read and available, an event called GotValue occurs.  A GotValue event handler processed the incoming data; in our simple app, the data is stored back in to the Value text box, on screen.


A unique feature of FirebaseDB is the database’s ability to alert apps that data inside the database has been changed. This alert caused a DataChanged event to occur – and which delivers the tag and value that were updated to the app.



FirebaseDB is experimental and incomplete, is subject to change, and should not be relied upon at this time for production code. However, you may use it for learning and experimentation.

Download Source Code

Download: FirebaseDB_Demo.aia

After downloading to your computer, you may upload the file to your App Inventor account using Projects | Import project (.aia) from my computer

Related Tutorials


Fewer professional coders in the future?

That is the actual future of software development: It will become so easy and second nature, that for ordinary tasks you won’t even have to think about it.

Source: Dear Google, the future is fewer people writing code | TechCrunch

Tools like MIT App Inventor, and others, are making programming so easy that it no longer requires extensive training and high levels skills to create many types of useful programs.


Writing code will become less and less necessary, making software development more accessible to everyone. This will allow people to solve new and unique problems for themselves, and true software engineers will continue to find ways to empower others through various platforms.

We used to call people who wrote programs, programmers. Later, this was change to titles like software developer, software engineer or sometimes computer engineer. Today, the media has short circuited the entire field to just “coders”, which seems like a downgrading of skills and title.

What is the FirebaseDB?

Hidden at the bottom of the Designer palette, is a category labeled Experimental and within that, there is a single item, the FirebaseDB:


What is FirebaseDB?

FirebaseDB provides a database “in the cloud” for your MIT App Inventor apps and supports the sharing of data between users simultaneously. When data in your FirebaseDB is changed, all apps are alerted to the updated data.

At this time, FirebaseDB is an experimental feature with critical limitations – notably you cannot yet set up your own personal FirebaseDB account but must instead use a single FirebaseDB run by MIT as a “shared account”. Sharing is limited to all users of a single app, and is not available between different apps.

FirebaseDB is Similar to TinyWebDB

The programming interface for FirebaseDB is nearly the same as that used for TinyWebDB. TinyWebDB is a simple cloud-based database – to use, you need to set up the TinyWebDB on your own server or on Google’s servers. With your data stored in the “cloud”, your data may be shared among many apps.

For details on setting up and using TinyWebDB – including some tricks that enable sharing of TinyWebDB data between apps – please see my book,

  • App Inventor 2 Databases and Files (Volume 3 e-book)
    Step-by-step TinyDB, TinyWebDB, Fusion Tables and Files
    Buy from: Amazon, Google Books, Kobo Books

For more information, including a sample chapter, please see my App Inventor books page.

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What day is today? Finding the “Day of the Week” in App Inventor

A reader recently asked how to determine the day of the week – Monday, Tuesday, Wednesday and so on, using MIT App Inventor code. Obtaining the day of the week is easy, although not obvious.

Using TimePicker and DatePicker

I previously posted a tutorial titled “Using TimePicker and DatePicker for entering time and data information“. Refer to that tutorial for basic information on the handling of time and data information in App Inventor.

Converting Time Instants into Different Formats

App Inventor has built-in functions to convert the date into different formats. However, the function to convert a calendar date into the day of the week is not in the DatePicker component, but in the Clock component.

To demonstrate, we use the original app from the TimePicker and DatePicker tutorial (you may download the sample code from the original tutorial page) and then we add two small bits of code to do identify the day of the week.

In the original sample code, the screen’s Initialize event handler displays the current date and time on screen. To that code, we add the block shown within the yellow rectangle, below:

Voila_Capture 2016-08-01_03-02-47_PM

call Clock1.Now” returns a value called a time instant. The time instant contains both date and time in a special format: the format is not important to us as App Inventor provides routines to convert the time instant into common values like year or hours and minutes.

The Clock component has a method “call Clock1.WeekdayName” that extracts the date information and calculates the day of the week, returning a text string with values like “Sunday” or “Monday”.

In the original tutorial, the DatePicker is used to select a new calendar date (different than what ever the current date is). Once the data is selected with that user interface, the event “.AfterDateSet” is thrown. Within the AfterDateSet event handler, we extract the Year, Month, Day and also the “WeekdayName” name. To convert the date instant to a day of the week format, we use the WeekdayName method of the Clock component – easy but not obvious!

Voila_Capture 2016-08-01_03-03-18_PM


Converting a date or time instance into normal formats like Year, Month, Day or day of the week is easy when you use the appropriate conversion functions built in to the App Inventor components.

The weekday value conversion is a little odd in that its hidden in the Clock component. But once you find it, obtaining the day of the week is easy!

Introducing my “Internet of Things” Blog

The “Internet of Things” refers to connecting all types of products and sensors to the Internet.

Sensors, microcontrollers and communications are so inexpensive they can be built in to many objects and devices.

For example, a light bulb (or light switch) can detect the presence or absence of people in a room – and automatically turn a light on or off. A light bulb that can detect people in a room could also become part of a security system by transmitting the room status to another device (security alarm) or to a smart phone app or to an Internet application running in “the cloud”.

In this way, a “dumb” device (light bulb) becomes enhanced to perform new functions and become more valuable than “just a light”.

The Internet of Things (or IoT) refers to adding sensors, controllers and communications to all sorts of “things”. Devices become connected to the Internet – and even our lightbulbs might end up with IP addresses!

I just launched a new web site – “Coldstreams Internet of Things” – that will focus on the Internet of Things, and the related subjects of robotics and automation.

Regarding robotics and automation, the same inexpensive technology that makes IoT possible is creating new opportunities for robotics and automation. We will see the development and adoption of new kinds of automation, far sooner than most people realize. These technologies are not in the distant future but are available now, particularly in business and industry.

To visit the web site, go here: Coldstreams Internet of Things

Follow on Facebook here:

While IoT is separate from App Inventor, there will be overlap. I am sure many of us are dreaming of MIT App Inventor apps that interface with external devices! I know I am!

Why the name Coldstreams? Long story but I’ve had that name and URL for a very long time. It was used in the past for a small business and then for a blog on technology and business. I have relaunched the web site to focus on Internet of Things. That said, about 2,000 original and now dated blog posts are still there – and on the Facebook page!