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All right, so I want to talk about Ruby and Ruby-like tools for Android. The first thing we need to address is how to get Ruby running on Android. Well, not exactly Ruby; we don't start with Ruby, because first, you have to install the Android SDK. That needs to be available so that you can run an emulator and build packages.
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You need to do that first, but then you can use a tool called Roboto, which is a modified version of JRuby that runs on Android. This is really cool! If you want to create an app using that, you first need to install the gem. I think the gem can actually be installed on MRI because it essentially controls the build process.
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The gem itself doesn't necessarily run your tests; it packages JRuby with your application, so you can generate an app using a command that specifies the version of Android you want to target, using the Android IDs provided. You will also need to specify the package name, as it still operates within the Java environment.
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This generates a whole bunch of files. I was going to show you the basic activity example that it generates, which can be quite verbose. So, Android has a concept of an activity, which is similar to a page on a web app—it has buttons and other elements.
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The default activity simply displays "Mr. Roboto" as the title and includes a button that changes some text when pressed. While this may not be particularly interesting, it gives you a basic idea of how to modify things. The initialize method behaves a bit differently on Android due to the object creation process.
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Now, let's talk about Ruby's role in all of this. There's also a project called Mirro, which is similar to Ruby but compiles directly to JVM bytecode and uses Java's object model. It resembles Ruby but differs in many ways. It also has a framework for writing Android applications.
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With that, you run a similar command to generate the necessary framework for your project. The code for projects using Mirro looks simpler, as shown in some example code I have.
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For instance, one example is an Android tutorial that walks you through creating a Sudoku game app. Just like the previous activity examples, in the onCreate method, you set up the state and listeners for the various components within your app.
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You will respond to different events, and the code typically resembles Ruby syntax. However, with Mirro, you will need to include some type information for the compiler to understand the types of objects you are using.
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If you inherit from existing classes, the compiler can infer the types more easily. This simplifies the coding process, which is pretty cool.
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I wrote a little test app called Guess My Number, which is a simple game. The game creates a random number and allows you to keep guessing it while tracking the number of attempts. You can ask the game for advice, and it will compare your last guess to the target number, letting you know whether you won or lost.
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I created an activity for this app; unfortunately, I don't have an emulator running right now, but if I did, I would show you how it works. You can click a button to make a guess and fill in a text field.
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The user interface isn't as polished as those created with RubyMotion. However, there is a fairly nice DSL for building UIs.
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You can download an app from the App Store that allows you to run Ruby code on your phone. There's even an IRB app for performing calculations on the go, which is pretty neat!
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Anyway, thanks for listening!