Chapter 1

Entering Mobile Application Development

In This Chapter

Identifying the market

Following the design process

Entering the world of object-oriented development

Mobile devices are everywhere. These smartphones and tablets run powerful applications and are making a difference in how people live, work, and play.

Many folks already use these devices as they do computers: to create and edit documents; to interact with others via e-mail, telephone, and chat; to play highly entertaining games; and to shop and manage money. Even schools, which used to ban cellphones in the classroom, are considering delivering educational materials to students via smartphones. Because they're common and robust, tablets and smartphones are now the primary computing and communication devices for many people.

A mobile device, in particular a smartphone, is more than a computing and communication device, however. Because it goes everywhere with you, you can be constantly connected to work and with other users. Also, because a smartphone can retain information about people you talk to, where you’ve been, and how much you spend, it in a sense "knows" you intimately. Mobile applications can take advantage of this device-user relationship to provide personalized and targeted services that users will depend upon and love.

Apps for a Mobile Platform

This book assumes that you’ve written applications for other platforms, such as desktop or laptop computers or the web. You can transfer a lot of this experience to writing applications for mobile devices like cellphones and tablets, including iOS devices.

However, when writing applications for iOS, you need to consider these differences:

• Tiny keyboards: iOS device keyboards make data entry very difficult. Data entry is no easy task to begin with, and touchscreen virtual keyboards, which you press with your thumbs, are prone to data-entry errors (for example, your app should provide smart spell-checking or allow the user to simply select from a set of options rather than making him type text).

  Some applications are created primarily to enter data (think Twitter or e-mail apps). However, try to limit data entry by doing things such as prefilling commonly used default values and providing drop-down lists that users can select from.

• Small display area: Displays on iOS devices come in these three shapes and sizes (see Figure 1-1):
  • 4-inch iPhone and iPod Touch
  • 7.9-inch iPad mini
  • 9.7-inch iPad

    Figure 1-1: Here are the three iOS device sizes.

  Compare these sizes to laptop screens, which are usually 15 inches or larger, and you’ll see what I mean by limited screen space.

  In order to be usable on small screens, an application must be designed so as to allow users to

  • Move intuitively in the program (without getting confused by a maze of screens).
  • Use controls (buttons, for example) that are large enough to press easily and place them in a way that helps to prevent click errors.
• Universal applications needed: In order for an iOS application to be popular, it must run on a range of devices with varied capabilities — that is, the iPhone, the iPad mini, and the 9.7-inch iPad (refer to Figure 1-1).

  Applications need to function well on the smallest and largest iOS displays.

  Note that previous generations of iOS devices had even smaller screens (iPhones prior to iOS 5 and iPod Touches prior to the 5th generation all had 3.5-inch displays). Also, Apple TV runs iOS. If Apple opens these platforms for app development with the latest iOS versions, the problem of creating universal apps will become even more complicated.

• Limited storage: iOS devices can store only about one-tenth of the information that PCs can, in both memory and persistent storage (flash or disk).

  Don’t store too many images, music, or (especially) video on the device because it can run out of space pretty darn quickly.

• Unreliable networks: It’s a fact of life: Mobile devices periodically lose network connectivity. Even when a device has a stable connection, the amount of data that can be sent or received varies based on the strength of the connection. So make your app
  • Buffer incoming data when the network connectivity is good.
  • Save outgoing data locally.
  • Receive and transmit data on a separate background thread.
• Device unavailability: A mobile device can be turned on and off depending on a user's situation (for example, when boarding a plane). A device can also be damaged (say, by being dropped), its computing speed can slowly degrade, and it can even shut down as its battery is consumed.

  Your application must deal with all these situations. For example, it could periodically check-point its state and have low-power modes of operation (for instance, a video-playing app might switch to playing only audio when the battery is low).

• A range of uses: Mobile devices are used in a variety of locations: rooms with low ambient lighting or sports stadiums with high levels of background noise, for example.

  Your applications must be able to adapt to these types of situations. For example, your app may lower the brightness of the screen when the ambient light is low or increase its audio volume when background noise is high.

• Coding in Objective-C: Apple made an early and highly innovative decision to base its development platform on Objective-C, well before standard object-oriented (sometimes referred to as OO) programming languages (such as Java, C++, and C#) came on the scene. Objective-C has an unusual syntax (as I explain in Chapter 3). It also has object-oriented semantics that are more like the early object-oriented languages like Smalltalk, but it's different from the later and now standard object-oriented languages like C++ and Java that most programmers are used to.

  Apple has provided a robust, highly reliable framework and excellent documentation to help build up strong skills in iOS app development.

iOS Benefits

Although many types of smartphones and mobile devices are still on the market today, the battle for market share is now pretty much between iOS and Android.

The lure of Apple and its wonderful set of innovative devices are what make the iOS platform so popular, and developing on the iOS platform offers you several benefits:

• Wide acceptance: iOS has legs — it’s inside millions of devices and is a major platform for application developers. So your app has a readymade market.
• Powerful, built-in, reusable capabilities: The iOS framework has lots of existing capabilities and services. It has built-in support for rich graphics, location finding, and data handling. In other words, you don’t have to write all the code for your application from scratch.
• Framework-based guidance for developers: Because iOS is a framework — not just a toolkit composed of a set of libraries — it imposes a structure on applications by using an application model. In return for this imposition, you receive a lot of benefits. You get to follow a systematic path in designing a robust application, which frees you to focus on providing rich capability rather than on figuring out the application's structure and high-level design or on nonfunctional tasks, such as managing your application's lifecycle. (You know what I mean — the starting-it-up stuff and the restoring-its-state-after-shutdown stuff, for example.)

Doing the sample application thing

This book uses a simple Tic-Tac-Toe game as an example. Each player claims a symbol, usually an O or an X. Players alternately place their symbol in empty locations on a 3 x 3 grid, with the goal of placing the same symbol in three grid spaces in a straight line, either in a horizontal row, a vertical column, or on a diagonal. The figure shows a sample sequence of plays. This Tic-Tac-Toe application allows two players to play against each other or for one player to play against the device.

You want the application to offer the following game-related functionality (in these examples, a user is playing against a computer):

• Allow the user to create a profile, consisting of a playing name and who goes first in the game — the user or the computer (see Chapter 6).
• Allow the user to start and play the game (see Chapter 7).
• Allow the user to exit the game at any time (see Chapter 10).
• Identify when the game progresses to a draw, a victory for the user, or a victory for the computer, and show the results (see Chapter 7).
• Record and save the results of a completed game (see Chapter 6).

In addition to the basic gameplay features, an application intended for the Android market needs to be robust: reliable and secure. Here I show you how to give the app these additional benefits (for more on these topics, see Chapter...