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Introduction to Xamarin

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How Xamarin Works

3:19 with Heath Hodgert

In this video we will discuss some of the elements that make Xamarin work for the iOS and Android operating systems. We'll see how the Xamarin platform leverages the powerful C# programing language to build native apps.

New Terms:

  • .NET -- Software framework developed by Microsoft
  • BCL -- Basic class library
  • JIT -- Just in time compilation
  • AOT -- Ahead of time compilation
  • SDK -- Software development kit

Further Reading:

Xamarin for Objective-C Developers
Xamarin for Java Developers
Getting Started: Xamarin Cross Platform
Binding iOS Native Libraries
Binding Java (Android) Native Libraries

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    Now that we've discussed some of the challenges with mobile development and 0:00
    how Xamarin can help, let's look at how it works. 0:04
    Each platform has its own feature set, application framework, and 0:09
    execution differences. 0:13
    Xamarin has Base Class Libraries, or 0:16
    BCLs which provide many features usually found in the .NET framework. 0:18
    They're implemented on the native platform and exposed through the BCL. 0:24
    For example, in the BCL there's support for Streams, IO, 0:29
    XML, Databases, and Networking. 0:32
    These provided base class libraries have the same signature as the dot net BCL. 0:38
    So we can write the same code for each platform. 0:44
    There are libraries provided by Xamarin that are included in each platform project 0:47
    that provide implementation for platform SDKs. 0:52
    All these features are plugged into Visual Studio and 0:57
    include IntelliSense, tools and compilation features. 1:00
    Xamarin provides bindings to the native libraries and SDKs for each platform. 1:06
    Bindings are strongly typed and are designed to follow C# standards. 1:12
    This gives developers a single consistent programming syntax 1:18
    regardless of the target platform. 1:22
    For example, Java does not have a concept of properties. 1:25
    So you use Get and Set methods to update a class variable. 1:29
    But, Xamarin wraps them in a property to match C# standards. 1:34
    Other than that, 1:38
    converting Java code to C# is relatively simple cuz they share a lot of syntax. 1:39
    For Objective-C developers, there are many differences between Objective-C and C#. 1:46
    So if you're converting from Objective-C, 1:52
    there's some articles in the teacher's notes to help with the transition. 1:54
    Xamarin also allows us to create an interop between 1:58
    any of our favorite Objective-C or Java libraries. 2:02
    Using a declared syntax we can bind any pre-existing library, and 2:06
    make it look like a C# class and use it in our app. 2:11
    Compilation is where all the magic happens, so 2:16
    we'll spend a few minutes talking about how it works. 2:19
    As I said earlier, Android and iOS have fundamental execution differences. 2:22
    Android uses a just in time execution model or 2:27
    JIT which means that it compiles to an intermediate language 2:30
    that is interpreted and executed when the app launches. 2:35
    iOS on the other hand uses an ahead-of-time execution model or 2:40
    AOT which means everything is compiled directly to native assembly code and 2:44
    nothing is interpreted. 2:49
    All of this compilation happens through special platform specific MS built targets 2:51
    that put all the pieces together and produce the executable artifacts. 2:57
    It's important to know when compiling for iOS you need a Mac. 3:02
    Because Apple's licensing does not permit compiling on any other platform. 3:06
    Android requires your target SDKs and 3:12
    tools to be on your machine, which can be downloaded when needed. 3:15

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