Developing C# Apps for iPhone and iPad using MonoTouch: iOS Apps Development for .NET Developers

500 Pages·2011·45.01 MB·English

by  Bryan Costanich

Companion
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Making .NET skills pay off
Developing C# Applications for iPhone and iPad using MonoTouch teaches you D in the iOS World
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how to use your existing C# skills to write apps for the iPhone and iPad.
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Over the course of the book, you’ll learn how to use MonoTouch to write C# l
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code that executes in iOS as a native app; you’ll take advantage of the unique
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functions of the iPhone, iPod Touch, and iPad; and you’ll integrate off-the-shelf
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Objective-C libraries in your C# apps. And the big plus? You needn’t learn any n
Objective-C to master MonoTouch. g

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Developing C# Applications for iPhone and iPad using MonoTouch takes you from #
your first Hello World example through the major APIs and features of iOS. The
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coverage is comprehensive and makes use of frequent examples, complete
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with sample code you can download and reuse to create your own powerful
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and playful apps. s

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What You’ll Learn: r
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How to use your existing C# skills to develop applications on iOS devices P
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Working with CocoaTouch’s UIKit to create iOS applications using native h
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controls
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Device-specific features, including the camera, GPS and compass,
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and the accelerometer
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• Accessing shared resources such as photos and contacts nd DDeevveellooppiinngg CC## AAppppss
• How to persist and retrieve data using SQLite and .NET libraries i
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Complex drawing and animation using Core Graphics and Core Animation
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This book shows you how to use the tools you already know to create native
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apps in iOS. You’ll master the elegant and rich Cocoa environment, provided by s iPhone iPad
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MonoTouch, without the need to learn a new programming language. You’ll be n
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writing apps for iOS devices with the minimum of fuss. for and using
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MonoTouch
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iOS Apps Development for .NET Developers
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ic Bryan Costanich
COMPANION eBOOK h
Shelve in:
Programming Languages / C#
SOURCE CODE ONLINE
User level:
www.apress.com Beginning–Intermediate
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For your convenience Apress has placed some of the front
matter material after the index. Please use the Bookmarks
and Contents at a Glance links to access them.
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Contents at a Glance
Contents .............................................................................................................. v
About the Author ............................................................................................... xiv
About the Technical Reviewer ........................................................................... xv
Acknowledgments ............................................................................................ xvi
Preface ............................................................................................................ xvii(cid:1)
■Chapter 1: Getting Started with MonoTouch ................................................... 1(cid:1)
■Chapter 2: Our First Application .................................................................... 11(cid:1)
■Chapter 3: Creating Multi-Screen Applications Using the MVC Pattern ........ 43(cid:1)
■Chapter 4: iPad and Universal (iPhone/iPad) Applications ........................... 59(cid:1)
■Chapter 5: More on Views and Controllers .................................................... 73(cid:1)
■Chapter 6: Introduction to Controls ............................................................... 93(cid:1)
■Chapter 7: Standard Controls ...................................................................... 107(cid:1)
■Chapter 8: Content Controls ........................................................................ 155(cid:1)
■Chapter 9: Working with Tables .................................................................. 193(cid:1)
■Chapter 10: Working with Keyboards .......................................................... 223(cid:1)
■Chapter 11: Multitasking ............................................................................. 233(cid:1)
■Chapter 12: Working with Touch ................................................................. 247(cid:1)
■Chapter 13: Working with Shared Resources .............................................. 271(cid:1)
■Chapter 14: User and Application Settings .................................................. 303(cid:1)
■Chapter 15: Working with CoreLocation ...................................................... 321(cid:1)
■Chapter 16: Drawing with CoreGraphics ..................................................... 331(cid:1)
■Chapter 17: Core Animation ........................................................................ 361(cid:1)
■Chapter 18: Notifications ............................................................................. 377(cid:1)
■Chapter 19: Working with Data ................................................................... 393(cid:1)
■Chapter 20: Publishing to the App Store ..................................................... 407(cid:1)
■Chapter 21: Third-Party Libraries ................................................................ 419(cid:1)
■Chapter 22: Using Objective-C Libraries and Code ...................................... 433(cid:1)
Index ............................................................................................................... 463
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1
Chapter
Getting Started with
MonoTouch
When most people think about developing applications for the iPhone, iPad, or iPod
Touch, they think of writing applications in a low-level language like Objective-C. But the
truth is, as the iOS ecosystem has matured, a number of ways to develop apps for it has
emerged.
The reason is largely developer-driven. For many developers, learning Objective-C was
seen as a huge barrier to entry. For .NET developers, many of whom have never had to
worry about memory management, pointers, and other C language concepts,
Objective-C also forced on them many responsibilities that they were unfamiliar with.
Many also feel that the tools for developing in Objective-C are lacking. Apple’s XCode
Integrated Development Environment (IDE) lacks many of the features found in other
modern IDEs, such as Visual Studio.
All this has changed, however, as more players have entered the iOS space. In addition
to MonoTouch, Adobe has entered it with Flash CS5, and Unity for the iOS powers some
of the best-selling games available on the iPhone and iPad.
The MonoTouch framework itself is part of Novell’s Mono project. The Mono project is an
open-source implementation of the Microsoft .NET platform published standards. It
allows you to run .NET applications on nearly any platform, including Apple, FreeBSD,
Linux, Unix, and others.
MonoTouch was introduced in the fall of 2009, and extends Mono by allowing you to write
applications using C# and the .NET platform Base Class Library (BCL) that run on the
iOS, using Cocoa Touch’s UIKit API.

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2 CHAPTER 1: Getting Started with MonoTouch
MonoTouch is an extremely powerful way to write applications for the iOS because it
combines a number of features:
(cid:1) Ability to call Objective-C, C, and C++: MonoTouch harnesses all the
power of low-level languages such as Objective-C, C, and C++. You
can use libraries written in Objective-C, et al. from your MonoTouch
code.
(cid:1) Modern language constructs: Because MonoTouch is based on the
.NET Platform, you get nearly all of the modern language features
available from it, such as automatic memory management, typed
exceptions, etc.
(cid:1) Modern IDE: The MonoDevelop IDE has all the features you have come
to expect in modern development environments, including automatic
code completion, an integrated debugger, intregrated source control,
and code refactoring tools.
Developing for the iPhone and iPad
The iPhone and iPad are tremendous devices, and MonoTouch goes a long way toward
making the transition between traditional .NET applications and applications for the iOS
easier. However, it’s important to take in consideration that developing for these devices
is very different than working with traditional .NET applications. Let's look at how mobile
development for the iOS differs from traditional application development.
Limited Multitasking
While the iOS v4.0 introduced multitasking to the iPhone 3GS (and newer) and the iPad,
it’s not true multitasking. In nearly any modern desktop operating system, multiple
applications can be running at once without issue. However, in the iOS, if your app
needs to keep processing when it’s not the foreground application, it needs to tell the
iOS what type of background tasks it wants to perform, and then it is given limited
processing time. Because of this, if you wish to support background processing, you
have to design your application very carefully. We’ll cover this in greater depth in
Chapter 11.
Limited System Resources
The iPhone has a very small amount of RAM (128MB for the 3G, 256MB for the 3GS and
iPad, and 512 for the iPhone 4). Because of the complex nature of the graphics that
support iPhone applications, and the fact that it’s fairly normal for OS processes to take
up more than half of your RAM, you can run out of memory very quickly on the iOS.
When the device is running low on memory, it will try and terminate known internal
memory-hungry applications (such as Safari) to reduce memory pressure, and then it will
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CHAPTER 1: Getting Started with MonoTouch 3
let your application know that the system is low on useable memory and you should
take steps to clean up unused objects in memory.
Small Screen Size
While the iPad sports a much larger screen (1024x768) than the iPhone (960x640 for the
4G and 320x480 for 3Gs and older models), they’re both small by comparison to the
standard screen size many desktop applications are built for.
While the iPad allows some flexibility in how you design screens, in the iPhone it’s
especially important to try to simplify screens into one task at a time in the UI. However,
this limitation is actually mitigated considerably by Apple’s UI Framework controls,
which are designed specifically to provide a pleasant and efficient user experience, even
with the small screen.
Device-specific Technology
Each device that runs the iOS may have different features specific to it. For instance, the
GPS and/or Compass feature isn’t available on all devices. Some devices have a camera
on the front, some devices can shoot video with their camera, some can only do still
photos. Some allow multitasking, some don’t. The list goes on and on.
Because of this, it’s important check for the presence of and ability to use a feature
before actually trying to use it.
Constrained Response Time
In order to retain the responsive feel that users have come to expect from iOS
applications, several operations in iOS are response-time sensitive. For instance, if your
application takes longer than ten seconds to start up, the iOS will abort its launch. When
a user clicks the home button to close your application, you have 5 seconds of
processing time to save any settings or state information before it’s terminated. The
same goes for multitasking features: your application is given a certain amount of time
to perform certain tasks, and if it fails, it can be terminated.
As a result, you need to design your application in such a way as to handle these
transitions very quickly in order to prevent the loss of state and/or data.
Constrained Access
iOS applications run in what’s called a sandbox. That is, they have limited permissions on
the device. For instance, they can only write files to their own directory, and can read
files from their directory and certain system directories. They can’t, for instance, write to
or read from any other application’s sandbox. They also can’t make low-level device
calls, etc. Therefore, when developing iOS applications, you must take this constrained
access into consideration.
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4 CHAPTER 1: Getting Started with MonoTouch
MonoTouch Background
Now that we have an understanding of the basics of iOS development, let’s examine
some of the basics of developing MonoTouch applications.
iPhone vs. iPod Touch vs iPad?
It’s important to note that developing for the iPod Touch is nearly identical to developing
for the iPhone, except for the fact that it doesn’t have a cellular radio. Additionally, both
the iPhone and the iPad run iOS and, besides User Interface (UI) concerns, developing
for them is nearly identical. We’ll explore the differences between them in Chapter 2.
How Does It Work?
The MonoTouch.dll (the base library that all MonoTouch applications are built against) is
equivalent to the Silverlight .NET 4.0 profile with some things added back in, such as
System.Data and System.Net. This allows you to write applications using many of the
.NET Framework technologies that you’re already familiar with, including Windows
Communication Framework (WCF), Workflow Foundation (WF), etc.
It also includes nearly all of the Base Class Library (BCL), including things like garbage
collection, threading, math functions, cryptography, and parallel processing framework.
For a list of available standard .NET assemblies in MonoTouch see
http://monotouch.net/Documentation/Assemblies.
This is accomplished through a MonoTouch-specific set of base .NET libraries, similar to
how Silverlight and Moonlight (Mono’s implementation of Silverlight) work.
This means that you can compile standard .NET 4.0 code libraries using the MonoTouch
core assemblies and use them in your application. So if, for example, you have a
specialized library that does advanced math functions for engineering problems that you
use for other applications, you can simply include the code library in your MonoTouch
solution, and reference it. When you build your solution, it will compile it using the
MonoTouch libraries, and it will then be available in your application.
MonoTouch also includes wrappers to the native iOS APIs, such as Location (GPS and
Compass), the accelerometer, address book, etc. It also gives you the ability to bind to
native Objective-C libraries that are not wrapped, so you can interop directly with
existing Objective-C code.
How Do I Build a User-Interface (UI); Can I Use Silverlight?
MonoTouch application UIs are typically built using Apple’s Interface Builder (IB)
application that ships with the iOS SDK. Interface Builder uses Cocoa Touch (Apple’s UI
Framework for iOS, also known as UIKit) objects that are native to the iOS. This means
that you have all the standard iOS controls available to your application, including
Pickers, Sliders, and Buttons, etc.
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CHAPTER 1: Getting Started with MonoTouch 5
You can also create your interface programmatically by instantiating Cocoa Touch
objects and adding them to your application’s Views (more on Views later).
You cannot, however, create your MonoTouch interface using traditional .NET
technologies such as Silverlight, WPF, or Winforms. You can, however, build games
using Microsoft’s XNA Toolkit that target the Windows 7 phone and port them using the
open-source XNA Touch project (we’ll cover this in Chapter 21). Additionally, there are
indications from the MonoTouch team that Moonlight will be supported at some point in
the future. Time will tell if that bears fruit.
Cocoa Touch uses a rough amalgamation of the Model View Controller (MVC) pattern
that we’ll discuss in Chapter 3.
By utilizing the UIKit, developers can make iOS applications using the same familiar
control set as applications written in Objective-C. However, if you wish to branch
beyond that, you can. MonoTouch also exposes the underlying graphics framework so
that you can create rich 2D and 3D applications that allow you to go well beyond the
UIKit control framework.
How Do I Distribute My Apps?
MonoTouch applications are distributed the exact same way that traditional iOS
applications are distributed, either via the Apple App Store, Enterprise, or ad-hoc
deployment.
The App Store is an online repository that allows users to pay for applications (if they’re
not free), and download them. It is available from within iTunes, or directly from the
iDevice itself. In order to get a license to distribute via the App Store, you must register
with Apple, and pay $99/year. For more information, go to http://developer.apple.com
and read about their development program.
Enterprise deployment is for those wishing to develop internal applications for a
company and distribute them, for example, to employees, without listing them with the
App Store.
Ad-hoc deployment allows you to deploy to a limited number of devices mainly for the
purpose of testing and development.
What Is the Licensing Model?
Unlike Mono, MonoTouch is not open source—it is a commercial product. That means, if
you want to do anything useful with it, you have to purchase a license to use it.
MonoTouch comes in three flavors and prices:
(cid:1) Professional ($399): A single personal developer license that allows
you to develop applications and distribute them via the Apple App-
Store
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6 CHAPTER 1: Getting Started with MonoTouch
(cid:1) Enterprise ($999): A single corporate developer license that allows
you to develop applications and distribute via the App-store, or via
enterprise deployment
(cid:1) Enterprise, 5 Seat ($3,999): The same as the Enterprise license, but
includes 5 seats
(cid:1) Academic ($99): A single personal developer license that only allows
non-commercial distribution via ad-hoc deployment
All three options include a year of free updates.
There is also an evaluation edition that allows you deploy to the simulator only (the
simulator is part of the iOS SDK, which I'll talk about later in this chapter). For the
purposes of most of this book, the evaluation edition of MonoTouch is all you need. If you
wish to try out any of your code on an actual device, you will have to purchase a
licensed copy of MonoTouch.
Are There Any Limitations of MonoTouch?
As powerful as MonoTouch is, it has some limations that the larger .NET Framework does
not. Let’s examine them.
No Just-in-Time (JIT) Compilation
Per Apple’s iOS policy, no application can include code that requires just-in-time (JIT)
compilation. But wait a second, that’s exactly how .NET works, right? This is correct;
however, the MonoTouch framework gets around this limitation by compiling your
application down to a native iOS assembly. This, however, introduces several limitations.
(cid:1) Generics: Generics are instantiated by the JIT compiler at run-time.
However, Mono has an ahead-of-time (AOT) compilation mode that will
generate all the methods and properties for things like List<T>. Other
uses of Generics, such as Generic virtual methods, P/Invokes in
Generic types, and value types that don’t exist in the core library in
Dictionary<TKey, TValue> are not supported (although there is a
workaround for Dictionary<TKey, TValue>).
(cid:1) Dynamic code generation: Because dynamic code generation
depends on the JIT compiler, there is no support for any dynamic
language compilation. This includes System.Reflection.Emit,
Remoting, runtime proxy generation for WCF, JIT’d RegEx, JIT’d
serializers, and the Dynamic Language Runtime.
C# Is Currently the Only Language
Additionally, currently, the only .NET language available for writing MonoTouch
applications is C#.
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CHAPTER 1: Getting Started with MonoTouch 7
More Information
For a full list of limitations and more information, including workarounds, see
http://monotouch.net/Documentation/Limitations.
Getting Started
In order to get started building MonoTouch applications for the iPhone we’ll need a few
things:
(cid:1) An Intel Mac computer running 10.6 (Snow Leopard) or better
(cid:1) The latest Apple iOS SDK
(cid:1) The current version of Mono
(cid:1) The MonoTouch SDK
(cid:1) An IDE such as MonoDevelop or XCode, or a text editor program
Mac Computer Running Snow Leopard
This is an important and easily missed requirement. While theoretically you could build
most of your application on other platforms, the iOS SDK (and therefore the iOS device
simulator and Interface Builder) are only available for Snow Leopard. Additionally, the
compiler itself uses some low-level magic specific to the Intel Mac machines, so having
one is an absolute must.
MonoTouch is currently working on tools that will allow you to write in Visual Studio via
their MonoTouch Tools for Visual Studio. However, it has yet to be released, and you
will still need a Snow Leopard machine to run the simulator and to compile for the actual
device.
Apple’s iOS SDK
Available at http://developer.apple.com/devcenter/ios, the iOS SDK is a free download,
but you must register with Apple to get access to it. Along the way, Apple may ask you
to pay $99 to get an iOS developer account, which allows you to deploy your
applications, but for the purposes of this tutorial, you just need the SDK. The iOS SDK
includes Interface Builder, the iOS device simulator, Xcode, and a few other things.
After you have installed the iOS SDK, make sure you can launch the iOS Simulator. You
can find the simulator by opening Spotlight and typing “iOS Simulator.”
Mono for OSX
Once you’ve tested out the iOS simulator, install the latest version of Mono for OSX.
Mono can be downloaded from http://mono-project.com/Downloads. Make sure you click
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