Lecture Mobile Application Development (119310)

iOS Development Introduction

Agenda

iOS Overview
- System Architecture, Runtime Environment
Application Life Cycle
Development Tools

iOS Overview - Facts

Formerly known as iPhone OS, introduced on 29th July 2007 with the Apple iPhone
Derived from Mac OS X, based on Darwin a free, Unix like OS
Kernel type: Hybrid
Supported platforms: ARM
Size: approx. 600 MB
Current version: 12.2
Current iOS devices: iPhone, iPod Touch, iPad, Apple TV (derivate tvOS), Apple Watch (derivate watchOS)

iOS Architecture

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Application Runtime Environment

Applications run in a UNIX based environment and have full support for threads, sockets, etc. but differences to Mac OS X exist, e.g.:
Virtual Memory
- Virtual Memory is constrained to physical available memory (no paging to disk)
- Read-only pages are released when more memory is needed
- No Garbage Collector
Multitasking (iOS > 4.0)
- Apps in background are suspended
- Apps can ask system for background execution

Application Runtime Environment

Security features
- Application sandbox
  - iOS Apps are restricted to a unique location in the file system
- File protection (iOS > 4.0)
  - Allows to encrypt files and make them inaccessible when the device is locked
- Keychain
  - similar to Mac OS X keychain, allows to store passwords
  - Stored outside the application sandbox

Application Structure

Each iOS app is composed of at least the following parts:

Datamodel (app dependent)
- Class: e.g. UIDocument
Controller
- Classes: UIApplication, UIViewController
- Protocol: UIApplicationDelegate
View
- Classes: UIWindow, UIView based classes

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Application Life Cycle

Different application states

State	Description
Not running	The application has not been launched or was running but was terminated by the system
Inactive	The application is running in the foreground but is currently not receiving events
Active	The application is running in the foreground and is receiving events.
Background	The application is in the background and executing code (only iOS > v.4)
Suspended	The application is in the background but is not executing code (only iOS > v.4)

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Application Life Cycle

Launching an application into the active state

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Application Life Cycle

Handling events

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Source: Apple

Application Life Cycle

Handling application interruptions

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Application Life Cycle

Moving an application to the background
If more time is needed the application can call beginBackgroundTaskWithExpirationHandler() within applicationDidEnterBackground()

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Application Life Cycle

Resuming foreground execution

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Application Life Cycle

iOS Memory Management example video by Fraser Speirs:

http://vimeo.com/34660348

Development Tools

Xcode: IDE including Debugger
- IDE for Mac OS X and iOS
- Sourcecode editor
- Debugging in simulator and remote on device supported
- Compiler: Apple LLVM Compiler
- Current version: 10.x

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Development Tools

Simulator (not an emulator)
Simulating the iOS devices using iOS libraries on Mac OS X
Uses Intel code, simulates GPS, multitouch (pressing alt), shaking the device and orientation changes
Logs error messages to console

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Development Tools

Interface Builder: tool for creating GUIs

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Development Tools

Storyboards: Interface Builder feature since Xcode 4.2, before using XIBs
Allows to specify screens and the triggers and transitions between them

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Development Tools

Instruments: tracing and profiling tool

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Assignment

Conduct iOS Assignment: First App
- Create your first simple iOS App using the Interface Builder

Recap Questions

iOS is based on which operation system?
What are the different states an iOS app can be in?
What is the purpose of the event queue?
What is the purpose of the event loop?
Can an iOS app run in the background and if yes, under which circumstances?
What is the difference concerning Memory Management between iOS and MacOS?