Cross-platform Mobile Development

Xamarin
Seminar
19th April 2012
Copyright 2012 © Xamarin Inc. All rights reserved

Agenda
Cross-Platform Mobile Development

Greg Shackles
Senior Software Engineer
OLO Online Ordering
greg@gregshackles.com

gregshackles.com
@gshackles
github.com/gshackles
Xamarin

Introduction
This session will discuss how to use C# to develop
iOS, Android and Windows Phone applications.

We’ll cover:

•Why use C#?
•Code sharing techniques and patterns
•Useful libraries

Xamarin

Native Platform Languages

Xamarin

Write Once, Run Anywhere?

!= !=

Xamarin

C# to the Rescue!

Xamarin

Beneﬁts

•C# and .NET are mature and powerful
•Skill reuse on all platforms
•Apps are still completely native
•Code can be reused across platforms
(even non-mobile platforms!)

Xamarin

Architecture
Mono#for#
UI# Silverlight# MonoTouch#
Android#

C## Business#Logic#

Run)me# .NET# Mono#

Pla/orm# WP7# iOS# Android#

Xamarin

What Code Can Be Shared?

•Most non-UI or platform code
•Core application logic
•Entities
•LINQ (objects, XML)
•Network access (System.Net)
Xamarin

Requirements
•MonoTouch
•Mac OS X
•MonoDevelop
•Mono for Android
•Mac OS X or Windows
•MonoDevelop or Visual Studio 2010
•Windows Phone
•Windows
•Visual Studio 2010

Xamarin

File Linking

•All profiles are not created equal
•Single copy of file
•Compile-time verification
•Project Linker extension for VS2010
http://msdn.microsoft.com/en-us/library/ff648745

Xamarin

Abstraction

•Separate common logic from UI
•Interfaces, base classes, etc.
public interface IContactManager
{
IList<Person> GetContacts();
}

public class AndroidContactManager : IContactManager
{
public IList<Person> GetContacts()
{

return null;
}
} Xamarin

Library: Xamarin.Mobile

•Abstraction layer over platform APIs
•Contacts
•Geolocation
•Camera
•...
http://xamarin.com/mobileapi

Xamarin

Observer Pattern

•Decouple UI from business logic
•Business layer can publish updates
•UI layer subscribes to updates
public EventHandler<EventArgs> MessageReceived;

MessageReceived += (sender, args) =>
{
Console.WriteLine("Message received");
};

Xamarin

Library: TinyMessenger

•Event aggregator/messenger
•Publish/subscribe
•Single ﬁle
•Supports iOS, Android, Windows Phone
https://github.com/grumpydev/TinyMessenger

Xamarin

Partial Classes and
Methods
public partial class MyClass
{
// partial methods are private, and must return void
partial void Foo();

public void Bar()
{
Foo();
}
}

public partial class MyClass
{
partial void Foo()
{
Console.WriteLine("Foo");
}
}

Xamarin

Conditional Compilation

#if __ANDROID__
Console.Write(“Only on Android”);
#elif WINDOWS_PHONE
Console.Write(“Only on Windows Phone”);
#else
Console.Write(“Everything else”);
#endif

Xamarin

Conditional Compilation
•MonoTouch
•No default symbols
•Mono for Android •Windows Phone
•__ANDROID__ •WINDOWS_PHONE
•__ANDROID_1__ •SILVERLIGHT
•__ANDROID_2__
•...

Xamarin

File Access
•Direct ﬁle access
•System.IO
•Works on iOS and Android
•Not supported by Windows Phone
•Paths are different on iOS and Android
File.WriteAllText(
Environment.GetFolderPath(Environment.SpecialFolder.Personal),
"Writing directly to a ﬁle");

Xamarin

File Access
•Isolated Storage
•Works on iOS, Android, and Windows Phone
•Higher level API
•Don’t need to worry about ﬁle paths

using (var store = IsolatedStorageFile.GetUserStoreForApplication())
using (var writer = store.OpenFile("MyFile", FileMode.Create))
{
// write to the ﬁle
}

Xamarin

Database Access

•iOS and Android
•SQLite
•Native APIs or ADO.NET
•Windows Phone
•SQL Server CE
•LINQ to SQL
Xamarin

Library: C#-SQLite

•C# port of SQLite database
•File based
•Useful for Windows Phone, Silverlight
http://code.google.com/p/csharp-sqlite

Xamarin

Library: sqlite-net

•Layer over SQLite database
•Strongly-typed queries
•Single ﬁle
http://code.google.com/p/sqlite-net

Xamarin

Library: TinyIoC

•Inversion of Control container
•Single ﬁle
https://github.com/grumpydev/TinyIoC

Xamarin

Library: MonoCross

•Cross-platform MVC framework
•Shared models and controllers
•Views speciﬁc to platforms
•Sits atop MonoTouch, Mono for Android
http://code.google.com/p/monocross/
Xamarin

More Links

MWC 2012 App
https://github.com/xamarin/mobile-samples/tree/master/MWC

NYC Code Camp 6 App
https://github.com/gshackles/NycCodeCamp6

Mobile Development in C#
http://amzn.com/1449320236

Xamarin

Xamarin
Seminar
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19th April 2012

Cross-platform Mobile Development

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