Global Nerdy

Android

Click the screenshot to see it at full size.

• Android Studio 2.0 is out of beta and in general release! Among the goodies in this version are:
  • a much faster, more fully-featured emulator,
  • faster builds with Instant Run
  • Cloud test lab integration to test your app on a wide variety of devices from within Android Studio
  • Better findability for your app in Google searches via app indexing code generation and test
  • GPU debugger preview for OpenGL-based development
  • IDE features from IntelliJ 15
• Smaller, faster Android apps with ReDex. Facebook uses ReDex, their in-house bytecode-optimizing tool, to make their apps faster and smaller, and they’re now open sourcing their tool and making it available for all Android developers. Here’s the link to the GutHub repo.
• Rumors that Google is considering making Swift a “first class” language for Android development. The Next Web says that they heard this from “sources”. Read the article, and follow it up with this one: 4 no-bull reasons why Swift on Android won’t come swiftly.
• Android Marshmallow (a.k.a. version 6.0, a.k.a. API 23) doubled from 2.3% to 4.6% over the month of March. I’m part of that statistic, as the update for my 2nd-gen Moto G came out during that time, and I installed it.

Regrets and mistakes, part one

This question appeared on Server Fault on Sunday:

I run a small hosting provider with more or less 1535 customers and I use Ansible to automate some operations to be run on all servers. Last night I accidentally ran, on all servers, a Bash script with a rm -rf {foo}/{bar} with those variables undefined due to a bug in the code above this line.

All servers got deleted and the offsite backups too because the remote storage was mounted just before by the same script (that is a backup maintenance script).

How I can recover from a rm -rf / now in a timely manner?

Most of the answers were along the lines of: “If you’ve got backups, you’ll be fine. If you don’t, you’re about to go out of business.”

iOS and Swift

• If you read only one blog about Swift programming, make it Erica Sadun’s. She’s forgotten more about iOS development that I’ll ever learn. In a recent post, she tells us all about getting ready for the API pruning that’ll happen when Swift 3.0 — which is coming soon — is released.
• When to use an enum, and when to use a protocol. Be sure to read the whole thing, but the practical upshot is, if you’re trying to represent a finite number of cases or variants for a type, such as days of the week, shirt sizes, planets, and so on, an enum will work just fine. However, the more you’re trying to model different behaviors or add functionality for each case or variant, and especially if you expect to add more cases or variants, you’re probably better off going with a protocol or class.
• Here’s a good reason to avoid using class names in #selector.
• This one intrigued me, so I bookmarked it for my own reading later: Oscar Swanros explains how he deals with JSON in Swift.
• If you’re an experienced Swift developer and are willing to move to Cupertino, your dream job just opened up:
  

  We’re hiring on the Swift team. We don’t need wizards, rockstars, or ninjas, just experienced devs interested in compilers. Hit up @jopamer!

  — Joe Groff (@jckarter) April 11, 2016

Regrets and mistakes, part two

From My Biggest Regret as a Programmer:

I could go on and on but the key is that you can’t make changes in how people do things in a technical sense unless you have the ability, the authority and the opportunity. Once you make that call and assuming you find the right places to grow, the sky is really the limit.

When I was on TV (Computer Chronicles) in early 1987 showing our product Trapeze the other presenter was Mike Slade who was product manager of Excel. At the time young me thought him some random marketing weenie (young people can be pretty stupid). Yet he started all these companies later including ESPN, worked for Apple in various leadership roles, was a good friend of Steve Jobs and started his own VC firm.

And today I am still just a programmer. Who’s the weenie now? I doubt I will ever be able to really retire. Thankfully I am still good at delivery (I was recruited into my present job by a former manager who needed what he knew I can do) but still all I will be until I croak is what I am now.

Marvel Comics are doing some interesting things with characters that aren’t that well-known outside comic book fandom, not just with the Guardians of the Galaxy, a (very radically altered) Big Hero 6, and Ant-Man on the big screen and Jessica Jones, Peggy Carter, and various agents of S.H.I.E.L.D. on smaller ones, but even in their comic books, with Ms. Marvel and, more recently, the incredibly cute and unbeatable (it says right so in the title) Squirrel Girl.

Conceived as a throw-away character in the early ’90s when most comic book series were trying to be like The Dark Knight Returns, the 1982 Wolverine solo series, or the X-Men, Squirrel Girl has become important enough to merit her own book, The Unbeatable Squirrel Girl, written by Ryan North of Dinosaur Comics fame.

Ryan North has a computer science background, with a bachelor’s degree from Ottawa’s Carleton University and a master’s from the University of Toronto (that’s right, he’s Canadian). That background is what drives some of Squirrel Girl’s story; when she’s not fighting criminals and supervillains, she’s Doreen Green, first-year student (that’s a Canadianism; most Americans would say freshman) of computer science at Empire State University.

Sometimes her computer science studies are the backdrop, as in this scene, where she shows up a little bit late for her class on databases…

…and other times, it plays a key role in defeating A-list supervillains like Victor von Doom. Doom’s primary flaw is that he’s a supreme egomaniac. Although he’s a science and engineering genius, he’s too proud to have learned programming languages that weren’t of his own design.

So when Squirrel Girl sends a message in C++ to her friends backing her up…

Click the comic to see it at full size.

(By the bye, here’s the code that she called out…)

string lw(int arr[], int arrsize) {
  string ret = "";
  for (int i = 0; i < arrsize; i++) {
    ret += itoa(arr[i]);
    return ret;
  }
}

lw({90, 65, 80, 77, 69, 87, 84, 73, 77, 
69, 77, 65, 67, 72, 73, 78, 69, 80, 76, 
90}, 20) + "!!!!!";

…Doom doesn’t understand what she’s saying, since he only programs robots in his own “Doomsembly language” and never learned any real programming languages because it would mean learning from others…

Click the comic to see it at full size.

Before you go spoiling the fun by saying “there’s no way you can formulate and yell out that code in that little time, and then have a friend do ASCII conversions in her head that quickly”, remember that all this is happening in a confrontation between a villain in a mechanical suit powered by both super-science and sorcery and a young woman with squirrel powers.

Also amusing: how the comic book often starts with Twitter conversations:

In case you’re wondering, the jingle she’s referring to is from the 1960’s Iron Man cartoon…

…and it gets referenced in the first Iron Man movie as his mobile phone ringtone…

The Unbeatable Squirrel Girl is a fun read, and the computer science bits just make it even more fun for a former computer science major like myself.

Keeping an eye out for mobile device procurement fraud

 

In the CFO.com article, Cell Phone Fraud: Who’s Watching IT?, corporate forensics specialists Jesse Daves and Celyna Frost talk about the very profitable business of mobile device procurement fraud. With aftermarket prices for a new iPhone 6S ranging from $1,000 in the U.S. to as much as $3,000 in China, it’s often tempting for people in IT departments to use their authority and access to procure mobile devices on their company’s behalf using company funds, make them disappear from the books and resell them at a completely cost-free profit.

Without the internal controls and systems to provide visibility into its inventory and procurement process, it’s much simpler for internal fraud. The article lists a number of “red flags” that indicate the potential for procurement fraud, including:

• IT’s resistance to sharing access to the mobile provider’s billing web portal
• When accounts payable receives only a summary of the mobile bill
• Blanket charges that are simply summarized as “international data charges” or “roaming fees” without any substantiation
• An unusual number of suspended or frozen accounts
• Unusually large orders of devices
• Recurring shipments to unknown parties

Suggestions for reducing the likeliness of mobile procurement fraud include:

• Separating responsibilities so that employees with the authority to order equipment are not the same ones as those who receive them upon delivery
• Controlling the process for payment approval and cost allocations (one fraud trick is to allocate costs for improperly-purchased goods to another business unit)
• Maintaining comprehensive and complete records so that every item on every bill can be traced back to a device, circuit, or service in the company’s telecom inventory
• Performing regular audits to ensure that all telecom charges can be connected to valid employees.

In the end, clear visibility into your telecom environment is your best defense against internal fraud.

Mobile Ate the World: A presentation by Andreesen Horowitz

Benedict Evans of $4 billion venture capital firm Andreesen Horowitz gave a presentation at The Guardian’s Changing Media Summit titled Mobile Ate the World, a play on his firm’s motto, “Software is eating the world”.

In it, he talks about how mobile is now the universal technology, scaling up to everyone on earth…

…how mobile isn’t just a screen size, but an ecosystem…

 

…and how mobile doesn’t just mean “mobile” — a lot of mobile use happens at home, and nearly 50% of smartphone traffic happens on wifi:

If you’re as interested in the future of mobile as we are, it’s worth reading Mobile Ate the World.

RootMetrics’ Mobile Network Performance in the US report

The cellular carriers are in hot competition and expanding the reach of their LTE networks and grow their network capacities — how are they doing, and who’s offering the fastest and most reliable mobile experiences? The cellular analytics firm RootMetrics published regular reports on this topic, and their latest one looks at the service offered by AT&T, Sprint, T-Mobile, and Verizon in the second half of 2015.

ExpressJet replaces 50-pound flight bags with Surface tablets running Windows 10

If you fly often, you’ve probably seen pilots walking to or from their flights lugging large bags like one pictured above (perhaps not as well-worn). These flight bags have traditionally carried a lot of paper documentation in binders: operating manuals, navigation charts, reference handbooks, flight checklists, logbooks and weather information, and together, they can weigh anywhere from 30 to 50 pounds. This documentation is updated regularly, so often before each flight, pilots have to collect updated documentation, remove the outdated material from their binders and insert the new pages. It’s a lot of paperwork to lug around and sort through; now imaging trying to find a key piece of information while you’re trying to fly a plane at the same time.

As far back as 2011 — a mere year after the introduction of the iPad — airlines have been replacing all this paper documentation with “EFBs” (Electronic Flight Bags), which are tablets running apps specifically designed for pilots. United Airlines committed to deploying 11,000 iPads running Jeppesen’s FliteDeck app to pilots as their EFBs in the late summer of 2011, and more recently, ExpressJet got FAA approval to hand out Surface 3s running Windows 10 to their pilots to replace all that paper that went into their flight bags.

Here’s a video by Microsoft with ExpressJet pilot Renee Devereux talking about her new Surface 3 EFB:

The electronic flight bag is a good example of mobile devices playing to their strengths in the workplace:

• As electronic replacements for large volumes of often-updated paper documents
• Providing quick access to crucial data in routine and (literally!) mission-critical scenarios
• Portable computing devices with significantly greater battery life than traditional laptops
• An employee perk (as shown in the video, ExpressJet pilots are allowed to use their tablets to stay in touch with their families while on the “road”)

This roundup of mobile developer news has a theme: making money with your apps, with both practical advice and tutorials, as well as bigger-picture discussions of the topic.

Under the Radar is David Smith and Marco Arment’s podcast on indie iOS app development. They make sure that none of their podcasts runs longer than half an hour. Their latest podcast, the 21st in the series, is titled App Store Rejection, in which they provide suggestions on how to avoid rejections from Apple’s App Store review staff, and what to do when your app gets rejected.

Their two previous podcasts also cover the App Store: Improving the App Store, Part 1 and Improving the App Store, Part 2.

I had no idea that mobile games were a bigger business than PC and console gaming. Here are the sizes of the game markets, according to App Annie and IDC:

• Mobile games are a $34.8 billion market worldwide,
• PC/Mac games are a $29 billion market,
• Console games are an $18.5 billion market, and
• Games for handheld game devices are a $3 billion market.

At the time of writing,”Application Category Distribution” section of PocketGamer.biz’s App Store metrics page showed the following breakdown of apps:

1. Games (527,017 active)
2. Business (234,930 active)
3. Education (210,991 active)
4. Lifestyle (198,844 active)
5. Entertainment (144,613 active)

They also report these numbers for app pricing:

• Current Average App Price: $1.12
• Current Average Game Price: $0.54
• Current Average Overall Price: $0.99

Ray Wenderlich’s site may have started out as iOS-specific, but they’ve expanded their coverage to include Android and Unity development. Their latest Android article is titled Android App Distribution Tutorial: From Zero to Google Play Store, and it shows you how to get your newly-created Android app into Google Play’s store.

App Annie, the mobile app analytics service, published their inaugural app economy forecast a couple of months ago, where they make the following predictions:

• This year, the global app market is expected to grow 24% and hit $51 billion in gross revenues across all app stores
• The global app market will exceed $100 billion is gross revenues by 2020
• China surpassed the US in mobile app downloads last year, and is expected to surpass them in app spending this year.

In-app purchases can help you generate more money with your apps, and this article can help you with setting them up on iOS apps: In-App Purchase Tutorial: Getting Started.

In case you missed it, The Verge recently published Life and Death in the App Store, an article which on one level is the story of Pixite, a mobile development shop that had some early successes and is now treading water, and on another level is the story of the changes in the app market between its inception less than a decade ago and the present day, and what that means for developers who plan to make a living off it.

About 150 airports in the U.S. have TSA PreCheck, an expedited security line for pre-screened travellers. If you fly often, you’ll find it very convenient as the line’s usually short, and you can forego having to remove your shoes, jacket, and belt, as well as having to separate your laptop and “3-1-1 liquids” from the rest of your carry-on luggage. There is a price to be paid for this — a registration fee, along with providing the U.S. Customs and Border Protection agency enough info to do a background check on you, and there’s an interview as well. If you’re an American or Canadian with a NEXUS card, you’re already in the TSA PreCheck program.

Even the pre-screened people going through TSA PreCheck get some additional random screening every now and again. The TSA PreCheck line often has two lanes, one on the left, one on the right, and they pick people for additional security screenings from one of them. In order to keep people from trying to guess which line that is, the TSA commissioned the development of a “randomizer”, which is an iPad app that randomly determines which line you should use.

The video below shows the randomizer in action:

The app would make a good “iPad programming 101” assignment; a newbie developer should be able to complete it in a day, and someone with even a couple of months’ of experience should be able to complete it in an hour.

Developer Kevin Burke wondered how much the TSA paid to have the app developed. As a government agency, they’d have put out an RFP to companies that do contracts for government work, and none of them come cheap. He filed a Freedom of Information Act request, and mirabile dictu, he got some answers in the form of two documents:

• A letter explaining that some of the information they provided had to be redacted, and
• a contract dated September 30, 2013 between the TSA and the development contractor, IBM.

Here’s the most eye-catching part of the contract:

Burke posted his findings online, and Pratheek Rabala, who does interactive graphics for TIME, pointed out that not only the information was readily available to the public, but that the payment shown above was just one in a series of payments totalling $1.4 million.

It turns out that the $1.4 million dollars covers the cost of a larger project, which includes other mobile applications, software to support an “enhanced staffing model” for the TSA, and all the project management that such an undertaking requires.

The TSA, when asked, pointed out that the “development costs for the TSA Randomizer Application were $47,400 in total.”

With that in mind, it’s time to fire up Xcode and start on the path to that sweet, sweet government contract money. Why should IBM have all the fun?

If you’re new to iOS programming or even programming in general, the TSA Randomizer app is a good starter project. You might want to try writing it on your own before following the steps below. Here’s a hint that should help — you’ll need to know how to do these things in order to write the app:

• How to generate a random number
• How to display an image on the screen
• How to change the contents of an image on the screen
• How to know when the user has tapped on the screen

How to write the app

Open up Xcode and do the File → New → Project… dance. As you may have already suspected, you’re going to specify that this is a Single View Application:

Give the project a name (I called mine TSARandomizer), and select iPad from the Devices drop-down menu:

Once you’ve chosen a place to save the project and it’s been written to disk, you’ll be taken to the General page for your project. Under Device Orientation, make sure that Portrait is checked and that all other orientations are unchecked:

Click the screenshot to see it at full size.

Edit ViewController.swift and change its contents to the following:

import UIKit

class ViewController: UIViewController {
  
  @IBOutlet weak var arrowImageView: UIImageView!
  
  let leftArrowImage = UIImage(named: "arrow-left")!
  let rightArrowImage = UIImage(named: "arrow-right")!

  override func viewDidLoad() {
    super.viewDidLoad()

    let tapGestureRecognizer = UITapGestureRecognizer(target:self, action:#selector(arrowImageViewTapped))
    arrowImageView.userInteractionEnabled = true
    arrowImageView.addGestureRecognizer(tapGestureRecognizer)
    
    displayRandomizedArrow()
  }

  override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
  }
  
  func arrowImageViewTapped() {
    displayRandomizedArrow()
  }
  
  func displayRandomizedArrow() {
    if arc4random_uniform(10) < 5 {
      arrowImageView.image = leftArrowImage
    }
    else {
      arrowImageView.image = rightArrowImage
    }
  }

}

This is all the logic needed to make the app work. The displayRandomizedArrow method is currently set so that 50% of the time, the left arrow is selected, and the other 50% of the time, the right arrow appears. You can adjust this to taste.

Time to build what little user interface there is. Open Main.storyboard and put an Image View control on the view. This will contain the arrows. We want it to fill up the screen, so set its constraints so that all its sides are 20 pixels from the view:

Click the screenshot to see it at full size.

In our code, we have an outlet variable named arrowImageView. We need to connect it to the image view we just added. Select the view and open the Connections Inspector. Drag from the circle to the right of New Referencing Outlet to the View Controller icon above the view, as shown in the screenshot below.

Click the screenshot to see it at full size.

Select arrowImageView from the pop-up menu that appears.

Click the screenshot to see it at full size.

Finally, we need to add the arrow images to our app: arrow-left.png and arrow-right.png. Open Assets.xcassets and drag the left-arrow and right-arrow images into it.

Click the screenshot to see it at full size.

Fire it up in the simulator or deploy it to your iPad, and start bidding on some TSA RFP’s — you’ve got a functioning TSA randomizer app!

I’ve zipped up my project and made it available for download (it’s a mere 300KB zipped). Enjoy!

One of the big changes that came from Microsoft’s acquisition of the cross-platform development tool company Xamarin is that their IDE, which once required a subscription fee for a version for building non-trivial projects, is now free-as-in-beer for the following:

• individual developers,
• small professional teams (5 or fewer users in an organization that isn’t considered an “enterprise”, which Microsoft defines an organization with more than 250 PCs or makes more than US$1 million in annual revenues),
• open source projects (that is, projects released under Open Source Initiative-approved licences),
• use in on-line or in-person classroom training and education, and
• use in academic research projects

If Windows is your development platform, Xamarin’s cross-platform mobile dev tools come baked into all editions of Visual Studio, even the free-as-in-beer Community Edition, which you can download from the Visual Studio page. If your preferred development platform is Mac OS, Xamarin Studio, a full-featured stand-alone IDE that borrows a few tricks from Visual Studio. In this article, I’ll take you on a quick tour of Xamarin Studio Community, as seen on my MacBook Pro, iPhone 6S, and Moto G running Android Marshmallow.

The installation process is pretty straightforward, and the length of time it takes will depend largely on your internet connection speed. Here’s a screenshot that I took of the installer at the start of the process:

Once installed, I did the oh-so-familiar File → New → Solution… dance and was presented with this window:

Note the options offered in the left column:

• Cross-platform development, which you can do in one of two ways:
  • Using Xamarin.Forms, a “universal” UI framework that allows you to target a single cross-platform UI that tries to be a native as possible on both Android and iOS, and
  • a more “traditional” way, where you write Android- and iOS-specific UI code while writing common logic that both with use
• iOS apps,
• Android apps,
• Mac applications, and
• “other” applications, which include:
  • console projects,
  • GTK# 2.0 projects,
  • NUnit libraries,
  • F# tutorials,
  • ASP.NET and ASP.NET MVC projects

For this walkthrough, I’m going to go with Xamarin.Forms to write something to deploy to both Android and iOS. When you do this, you’re presented with a couple of configuration dialogs, shown below. I’m going to name my project Magic8Ball…

Once past the configuration dialogs, you’re presented with your project. Xamarin Studio’s interface is a pretty standard IDE: solution tree in the left column, editor in the upper right-hand quadrant, and debug and console panes below the editor:

If you look at the left-hand solution tree column, you should notice that it’s divided into three parts:

1. Magic8Ball, the main project
2. Magic8Ball.Droid, the Android-specific parts of the solution, and
3. Magic8Ball.iOS, the iOS-specific parts of the solution.

Right now, Magic8Ball.iOS is marked in bold, which indicates that it’s the startup project. If you were to run the app right now with an iOS simulator as the target, here’s what you’d see:

Left-clicking on Magic8Ball.Droid and selecting Set As Startup Project makes it the startup project…

…and here’s what it looks like on the emulator. Note that Xamarin’s Android projects, by default, use a dark color scheme (which you can change with a simple configuration tweak):

In the newly-created “Hello World” template that you get when you first create a Xamarin.Forms solution, everything happens in the Application class instance. In the case of my app, that instance lives in Magic8Ball.cs. Not how the entire UI is set up in the constructor, App():

using System;
using Xamarin.Forms;

namespace Magic8Ball
{

	public class App : Application
	{
	
		public App ()
		{
			// The root page of your application
			MainPage = new ContentPage {
				Content = new StackLayout {
					VerticalOptions = LayoutOptions.Center,
					Children = {
						new Label {
							XAlign = TextAlignment.Center,
							Text = "Welcome to Xamarin Forms!"
						}
					}
				}
			};
		}

		protected override void OnStart ()
		{
			// Handle when your app starts
		}

		protected override void OnSleep ()
		{
			// Handle when your app sleeps
		}

		protected override void OnResume ()
		{
			// Handle when your app resumes
		}

	}

}

I changed the code to pass off the UI creation to a view class that I’m calling MainPage:

using System;
using Xamarin.Forms;

namespace Magic8Ball
{
	public class App : Application
	{

		public App ()
		{
			// The root page of your application
			MainPage = new MainPage();
		}

		protected override void OnStart ()
		{
			// Handle when your app starts
		}

		protected override void OnSleep ()
		{
			// Handle when your app sleeps
		}

		protected override void OnResume ()
		{
			// Handle when your app resumes
		}
	}

}

I decided to create a class called EightBall to handle all the predictions. Using File → New → File…, I was presented with the New File dialog, where I selected General on the left-hand column and Empty Class in the center column:

Here’s the contents of the file as given to me by Xamarin…

using System;

namespace Magic8Ball
{
	public class EightBall
	{
		public EightBall ()
		{
		}
	}
}

…and here it is once I’d filled it in:

using System;
using System.Collections.Generic;

namespace Magic8Ball
{
	public class EightBall
	{
		List<string> answers = new List<string>() {
			"Yes.",
			"Sure thing.",
			"But of course!",
			"I'd bet on it.",
			"AWWW YISSS!",
			"No.",
			"Nuh-uh.",
			"Absolutely not!",
			"I wouldn't bet on it",
			"HELL NO.",
			"Maybe",
			"Possibly...",
			"Ask again later.",
			"I can't be certain.",
			"Clouded by the Dark Side, the future is."
		};

		Random randomAnswerSelector = new Random();

		public string getAnswer() {
			return answers[randomAnswerSelector.Next(answers.Count)];
		}

	}
}

With the model class done, it was time for a view class, created with File → New → File… again. This time, I selected Forms from the left-hand column, and Forms ContentPage from the center column, specifying that I wanted a ContentPage, an onscreen container for containing a single view. It’s often used to represent a “screen” in an app:

Here’s the contents of the file when initially generated by Xamarin…

using System;

using Xamarin.Forms;

namespace Magic8Ball
{
	public class MainPage : ContentPage
	{
		public MyPage ()
		{
			Content = new StackLayout { 
				Children = {
					new Label { Text = "Hello ContentPage" }
				}
			};
		}
	}
}

…and here it is once I’ve defined my user interface and added a reference to the EightBall class:

using System;
using Xamarin.Forms;

namespace Magic8Ball
{
	public class MainPage : ContentPage
	{
		EightBall eightBall = new EightBall();

		public MainPage ()
		{
			var layout = new StackLayout {
				Padding = 20,
				VerticalOptions = LayoutOptions.Center
			};

			var answerButton = new Button {
				Text = "  I need an answer!  ",
				BackgroundColor = Color.Blue,
				TextColor = Color.White,
				FontSize = Device.GetNamedSize(NamedSize.Medium, typeof(Button)),
				FontAttributes = FontAttributes.Bold,
				HorizontalOptions = LayoutOptions.CenterAndExpand
			};

			var answerLabel = new Label {
				Text = " ",
				FontSize = Device.GetNamedSize(NamedSize.Large, typeof(Label)),
				FontAttributes = FontAttributes.Bold,
				HorizontalOptions = LayoutOptions.CenterAndExpand,
				XAlign = TextAlignment.Center
			};

			answerButton.Clicked += (object sender, EventArgs e) => {
				answerLabel.Text = eightBall.getAnswer();
			};

			layout.Children.Add (answerButton);
			layout.Children.Add (answerLabel); 

			Content = layout;
		}
	}
}

…and that’s it — we have a basic “Magic 8-Ball” app! Here’s what it looks like running on iOS 9…

Screenshot taken on my iPhone 6S running iOS 9.2.

…and here’s what it looks like running on Android Marshmallow:

Screenshot taken on my Moto G (second generation) running Android Marshmallow (6.0).

You can download the project (70KB zipped) to try it for yourself.

More about Xamarin

Charles Petzold, the guy who literally wrote the book on Windows development, was commissioned to write a book on building cross-platform mobile apps with Xamarin.Forms. At 27 chapters and nearly 1,200 pages, Creating Mobile Apps with Xamarin.Forms is the most complete document on the topic, and it’s free-as-in-beer to download. You’ll definitely want to get your hands on this.

For those of you looking for an online course, edX is offering a course called Introduction to Xamarin.Forms. It’s an introductory-level course, and is available for free. However, if you’d like to get a “Verified Certificate” for completing the course, you can apply for one for a mere $25.

The two videos below, shot at Microsoft’s recent Build 2016 conference, show more about Xamarin and its tools in action. Here’s the shorter one (27:19 long)…

…and here’s the longer one, running at one hour, which features a complete session from the conference, Cross-Platform Mobile with Xamarin: