iOS App Development

1  
SERIOUS  ABOUT  SOFTWARE


iOS
 App  Development  
Juha-­‐Ma5
 
Liukkonen
 
Mar  22,  2011  
Contents  
•
 
IntroducCon  to  the  
iOS
 PlaEorm  
•
 
iOS
 Concepts  for  SW  Designers  
•
 
App  Elements  
•
 
CreaCng  and  Deploying  an  App,  step-­‐by-­‐step  
•
 
Advanced  programming  topics  
•
 
DistribuCng  your  App  
 
Extensive  documentaCon  available  at:  
hNp://developer.apple.com
   
2  
Bonus  sector:  brief  introducCon  
to  Windows  Phone  7.  
3  
IntroducCon  to  
iOS
 
iOS
 Basics  
•
 
iOS
 is  a  low-­‐footprint  adaptaCon  of  Apple’s  Mac  OS  X  
•
 
Mach  microkernel  
•
 
BSD  
unix
 derived  libraries  and  
userland
 
•
 
ObjecCve  C  runCme  
•
 
Used  in  iPod  Touch,  
iPhone
,  
iPad
,  Apple  TV  
•
 
Touch  based  user  interface  
•
 
RevoluConized  the  industry  in  2007  
•
 
Mac’s  
AppKit
 replaced  with  touch-­‐centric  
UIKit
 layer  
•
 
Unix  layers  below  the  proprietary  
UIKit
 are  mostly  open  source  
•
 
So^ware  developed  using  ObjecCve  C/C++  
•
 
IniCally  Apple  aNempted  only  Web  apps,  but  that  didn’t  work…  
•
 
Code  runs  naCve,  effecCve  use  of  hardware  resources  
4  
iOS
 Architecture  
5  
The  Core  OS  is  shared  with  the  full  Mac  OS.  
Core  Services  is  a  subset  of  full  Mac  OS.  
Apps  are  wriNen  to  use  Cocoa  Touch  (
UIKit
)  
and  Media  services  layers.  
The  full  Mac  OS  X  has  a  wide  array  of  features,  
as  can  be  expected  from  a  desktop  OS.  There  
are  three  different  app  frameworks,  for  apps  
based  on  three  different  technologies.  
iOS
 APIs  and  compaCbility  
•
 
Apple  has  a  strict  2-­‐major-­‐versions  policy  
•
 
Older  so^ware  versions  are  deprecated  quickly  
•
 
So^ware  upgrades  are  free  and  easy  to  do  -­‐>  most  users  run  the  latest  version  
•
 
Currently  
iOS
 3  and  4  supported  
•
 
Only  the  oldest  devices  (
iPhone
,  iPod  Touch  1
st
 gen)  stuck  with  
iOS
 3  
•
 
iOS
 2  introduced  the  App  Store  (
iOS
 1  was  Web  apps  only)  
•
 
iOS
 3  is  single-­‐tasking,  but  introduced  lots  of  new  (even  basic)  features  
•
 
iOS
 4  =  current  version  
•
 
MulC-­‐tasking  –  having  mulCple  apps  in  memory  simultaneously  
•
 
FaceTime
 videoconferencing  
•
 
iBooks
,  
iAd
,  user  interface  tweaks  
6  
iOS
 variance  
•
 
Android  suffers  from  device  variance…  
iOS
 is  not  immune,  either  
7  
iPod
Touch
iPhone

3GS
iPhone
4
iPad

iPad
2
CPU
800 MHz
armv7
600 MHz
armv7
1 GHz
armv7
1 GHz
armv7
2x1 GHz
armv7
RAM
256 MB
256 MB
512 MB
256 MB
512 MB
Screen
960x640
480x320
960x640
1024x768
1024x768
Cameras
0.7 MP +
VGA front
3.2 MP
5 MP +
VGA front
-
0.7 MP +
VGA front
Sensors
Gyro
Compass,
Accel

Compass,
Accel
,
Gyro
Compass,
Accel

Compass,
Accel
,
Gyro
GPS
-
Yes
Yes
In 3G
models
In 3G
models
Note: only models currently in production.
iOS
 UI  basics  
8  
The  App-­‐centric  user  interface  is  iconic.  
No  widgets  or  distracCons,  just  a  quick  
launch  shortcut  bar  at  the  boNom,  and  
one  hardware  buNon  to  press  for  home.  
User  interface  elements  are  
large  and  easy  to  use  with  a  
finger.  
Text  input  is  performed  with  
an  on-­‐screen  virtual  keyboard.  
9  
iOS
 Concepts  
for  SW  Designers  
App  model  for  mobile  world  
•
 
ApplicaCon  model  inherited  from  Mac  OS  X  
•
 
TradiConal  C  
main()
 to  instanCate  UI  event  loop  
•
 
Strict  Model-­‐View-­‐Controller  hierarchy  
•
 
Data  Model  objects  manage  data  content  
•
 
View  Controller  objects  perform  view  setup  and  most  reacCve  acCons  
•
 
View  objects  manage  on-­‐screen  objects  
•
 
“Quick  launch,  short  use”  
•
 
UI  and  the  event  loop  are  set  up  as  first  things  (generated  code)  
•
 
Usually  View  Controller  
unserializes
 views  from  a  .nib  file  (generated  XML)  
•
 
All  code  is  naCve  
•
 
ObjecCve  C/C++,  preference  to  avoid  garbage  collecCon  
10  
Key for mobile app: save power.
Do work only when you have to.
ObjecCve  C/C++  
•
 
A  cross  between  Smalltalk  and  C/C++  
•
 
Some  say,  “object  oriented  C  done  right”  
•
 
SyntacCcally  quite  different  from  C++,  conceptually  not  so  much  
•
 
Significant  use  of  pre-­‐processor  direcCves  
•
 
Allows  for  run-­‐Cme  binding  of  objects  
•
 
Apple’s  FoundaCon  and  toolkit  libraries  rely  heavily  on  ObjecCve  C  features  
•
 
Original  design  from  
NextStep
 circa  1982  
•
 
Evolved  into  current  Mac  OS  X  circa  1998  
•
 
Proven,  flexible  and  very  
performant
 architecture  
11  
ObjecCve  C/C++  sample  
12  
@implementation
MyClass





- (
id)initWithString:(NSString
*)
aName


{


self = [super init];


if (self) {


name = [
aName
copy];


}


return self;


}





+ (
MyClass
*)
createMyClassWithString
: (
NSString
*)
aName


{


return [[[self
alloc
]
initWithString:aName
]
autorelease
];


}


@end


id
MyClass::initWithString(NSString
*
aName
)
{
this = ::init();
if (this) {
name =
aName
->copy();
}
return this;
}

static
MyClass
*
MyClass::createMyClassWithString(NSString
*
aName
)
{


return (new
MyClass
())->
initWithString(aName
));
}
Objective-C implements
reference counting and
garbage collection via
the
autoreleasepool
.
The  Model-­‐View-­‐Controller  
paNern  
•
 
Strict  separaCon  of  concerns  
•
 
Model  –  data  
•
 
View  –  display  
•
 
Controller  –  mediates  between  the  two,  understanding  applicaCon  state  
13  
The  Delegate  paNern  
•
 
Delegate  objects  handle  app-­‐specific  logic  
•
 
In  C++  or  Java,  you  create  specialized  subclasses  –  in  ObjecCve  C,  you  delegate  
14  
iOS
 app  logical  structure  
15  
iOS
 app  life  cycle  
16  
XCode
 and  Interface  Builder  
•
 
IDE  =  Integrated  Development  Environment  
•
 
XCode
 is  Apple’s  IDE  for  
iOS
 and  Mac  OS  development  
•
 
Code  compleCon,  online  help,  debugger,  deployment  to  target  device,  …  
•
 
Interface  Builder  for  building  the  UI  
•
 
Instruments  for  profiling  and  analyzing  
•
 
iPhone/iPad
 emulator  for  tesCng  
•
 
Also  used  to  manage  developer  idenCCes  
•
 
Must  have  a  developer  idenCty  to  deploy  apps  to  real  devices  
•
 
Developer  idenCty  obtained  from  Apple  Store,  67  €  /  year  
•
 
XCode
 3  is  free  for  everyone,  new  
XCode
 4  costs  4  €  for  non-­‐developers  
•
 
Registered  (i.e.  paid)  developers  get  the  new,  streamlined  IDE  for  free  
•
 
Based  on  screen  shots,  worth  the  investment  
17  
Ge5ng  ready  to  develop  
•
 
Follow  instrucCons  in  
hNp://developer.apple.com/
 
•
 
Download  
XCode
 3  or  4,  your  preference  
•
 
Run  the  installer  
•
 
OpConally:  run  
XCode
 and  enter  your  developer  informaCon  
•
 
Required  to  deploy  apps  to  real  devices  
•
 
Real  devices  are  recognized  when  they  are  plugged  in  
•
 
The  download  is  4+  GB  
•
 
InstallaCon  takes  another  30..45  minutes  but  is  generally  painless  
18  
Step 1: Get started
Step 2: …
Step 3: Victory!
19  
App  Elements  
The  
Info.plist
 file  
•
 
The  
Info.plist
 defines  your  applicaCon  
•
 
Display  name  of  your  applicaCon  
•
 
Executable  name  of  your  applicaCon  
•
 
Device  environment  that  your  applicaCon  may  require  (
iPhone/iPad
)  
•
 
Main  .nib  file  name  to  load  your  UI  from  (created  by  Interface  Builder)  
•
 
UIRequiredDeviceCapabiliCes
 to  require  GPS,  Camera,  etc.  
•
 
Cannot  request  all  differenCaCng  factors,  some  need  to  be  checked  in  code  
•
 
Important,  but  much  simpler  than  an  Android  Manifest  
•
 
Rarely  need  to  touch  the  
XCode
 generated  file  
20  
Resources  
•
 
Stored  in  subdirectory  
Resources  
in  your  applicaCon  source  tree  
•
 
Drawables
:  icons,  bitmaps  
•
 
Layouts  and  menus:  XML  view  definiCons  (the  .nib  and  .
xib
 files)  
•
 
Strings:  a  .strings  plain  text  file  mapping  logical  names  to  values  
•
 
LocalizaCon  
•
 
Get  Info  on  a  resource  file  in  
XCode
,  click  Make  Localizable  
•
 
Generates  a  copy  you  can  localize,  including  UI  layouts  and  graphics  
•
 
LocalizaCon  should  be  done  only  a^er  your  UI  layouts  are  final  
•
 
Command  line  tool  
ibtool
 can  be  used  to  synchronize  updates  
•
 
Results  in  
Language1.lproj
,  
Language2.lproj
 subdirectories  in  your  app  bundle  
•
 
System  will  load  resources  from  current  language  
.
lproj
 –  or  use  the  
development  language  defined  in  your  
Info.plist
 if  the  localizaCon  is  not  found  
21  
Source  files  
•
 
The  .
h
 files  for  declaraCons,  .
m
 files  for  code  
•
 
Forward  declaraCons  using  @class  
name
 
•
 
Interface  declaraCons  using  @interface  
name
 …  @end  
•
 
Class  member  
accessor
 declaraCons  using  @property  (…)  
name
 
•
 
Headers  included  using  tradiConal  #include  “
filename
”  
•
 
ImplementaCon  using  @implementaCon  
name  
…  @end  
•
 
Class  member  
accessor
 implementaCons  using  @synthesize  
name
 
•
 
AppDelegate
 implements  life  cycle  methods  
•
 
Including  instanCaCng  your  iniCal  view  
•
 
ViewController
 binds  your  views’  UI  elements  to  your  data  and  logic  
•
 
Implements  the  behavior  of  your  app  
22  
23  
CreaCng  and  Deploying  an  App  
Basic  steps  
•
 
In  
XCode
,  File  -­‐>  Create  New  Project,  
iOS
 ApplicaCon  
•
 
Select  the  View-­‐based  ApplicaCon  to  get  a  View  and  a  Controller  
•
 
XCode
 generates  the  directory  structure  and  skeleton  files  for  you  
•
 
Add  funcConality  to  your  
ObjC
 code  
•
 
For  example,  a  buNon  click  handler  
•
 
Add  resources  
•
 
For  example,  a  picture  (drag-­‐and-­‐drop  to  Resources  folder)  
•
 
Open  the  
.
xib
 
file  and  add  some  user  interface  elements  
•
 
E.g.  a  buNon;  bind  your  code  objects  to  UI  objects  with  drag-­‐and-­‐drop  
•
 
Run  your  app!  
•
 
Either  in  emulator,  or  over  USB  on  your  
iOS
 device  (if  you  have  paid!)  
24  
XCode
:  create  
iOS
 project  
25  
XCode
:  project  structure  
26  
XCode
:  add  UI  elements  
27  
XCode
:  add  resources  
28  
IB:  Add  UI  elements  
29  
IB:  Bind  code  to  UI  
30  
Right-click
Drag the circle to
the UI object to bind to
XCode
/IB:  localizaCon  
31  
The last step is to edit all .
xib
file
variants in Interface Builder for
proper localization.
XCode
:  run  on  Target!  
32  
Click the “Run” button
in the
XCode
toolbar.

If you have an
iOS

device, your app can run
directly in your device.
Choose your target in
XCode
.
33  
Advanced  programming  topics  
State  saving  
•
 
When  user  presses  the  Home  buNon,  
•
 
In  
iOS
 3,  your  app  will  be  killed  –  
iOS
 invokes  your  delegate’s  
applica;onWillTerminate
   
•
 
In  
iOS
 4,  your  app  will  remain  in  memory  –  
iOS
 invokes  your  delegate’s  
applica;onDidEnterBackground
   
•
 
Even  in  
iOS
 4,  if  resources  become  scarce,  your  app  will  be  killed  
•
 
Best  to  save  state  in  a  dicConary
 
(name,  value  pairs)  whenever  either  state  
change  method  is  invoked  by  
iOS
 
•
 
When  your  app  starts  up  
•
 
In  your  delegate’s  
applica;on:didFinishLaunchingWithOp;ons
 
method,  read  
and  restore  your  state  data  from  the  parameter  dicConary  (if  not  
nil
)  
•
 
Data  stored  as  (an  XML  format)  
plist
 
in  your  app  configuraCon  area  
34  
Game  programming  
•
 
iOS
 apps  run  naCve  code  
•
 
Maximum  performance  
•
 
All  hardware  resources  in  use  
•
 
Direct  access  to  OpenGL  ES  
•
 
Complex  3D  user  interfaces  possible  
•
 
Need  to  honor  the  app  life  cycle  noCficaCons  
•
 
Immediately  stop  animaCons,  sounds,  etc  when  told  to  go  to  background  
•
 
Device  must  react  to  incoming  calls,  SMS,  etc  immediately  
35  
36  
DistribuCng  your  App  
The  App  Store  
•
 
The  definiCve  on-­‐line  app  store  
•
 
300000  app  Ctles  (Android:  200000)  
•
 
62000  unique  developers  (Android:  180000)  
•
 
33%  free  apps,  66%  paid  apps  (Android:  60%  free,  40%  paid)  
•
 
Average  paid  app  price  in  2010:  $2,43  
•
 
50%  of  apps  between  $0,99  ..  $2,99,  only  1%  at  $24,99  or  more  
•
 
30%  of  revenue  goes  to  Apple,  70%  to  developer  (out  of  which  you  pay  taxes)  
•
 
The  67  €  /  year  fee  buys  you  fairly  good  QA  
•
 
Easy  to  submit  apps  to  the  Store  
•
 
Apple  engineers  verify  that  your  app  works,  keeps  quality  high  
•
 
Apple  has  a  strict  acceptance  policy  
•
 
Any  content  which  
might
 get  Apple  into  liability  court  is  rejected  /  removed  
37  
In  Conclusion  
•
 
Apple’s  
iOS
 sets  the  bar  for  others  
•
 
Harded
 to  get  into  than  Android  –  ObjecCve-­‐C  language  and  fairly  complicated  
design  paNerns  required  
•
 
NaCve  code  runs  efficiently,  maximum  performance  and  capabiliCes  
•
 
Has  a  reputaCon  of  high  quality,  people  expect  that  and  are  willing  to  pay  
•
 
Developer  tools  extensive  but  fairly  complicated  
•
 
New  
XCode
 4  streamlines  development  
•
 
Excellent  and  extensive  documentaCon  
•
 
Sample  code  in  developer  portal  (requires  membership  =  money)  
•
 
Rich  and  mature  APIs  
•
 
Data  access,  mulCmedia,  wireless  services,  …  
•
 
Reasonably  easy  to  create  simple  apps,  complex  apps  require  liNle  more  
38  
39  
Quick  IntroducCon  to  WP7  
Windows  Phone  7  basics  
•
 
Based  on  Windows  CE  6.0,  replaces  clunky  Windows  Mobile  6.5  
•
 
All  APIs  now  .NET  based,  no  direct  C/C++  API  
•
 
Simple  apps  using  
Silverlight
 and  C#  assemblies  
•
 
Games  using  XNA  and  C#  assemblies  
•
 
Strict  conformance  requirements  for  devices  
•
 
800x480  
mulCtouch
 display,  512  MB,  armv7,  camera,  hardware  keys,  …  
•
 
Very  specific  look  and  feel,  which  cannot  be  skinned  by  device  vendors  
•
 
Microso^’s  aNempt  to  curb  variance  and  fragmentaCon  of  app  ecosystem  
•
 
Limited  possibility  for  device  vendors  to  differenCate  from  others  
•
 
Many  device  vendors  embracing  WP7  
•
 
LG,  Samsung,  most  famously  now  also  Nokia  
•
 
Trust  that  Microso^’s  markeCng  muscle  will  sell  devices  
40  
WP7  APIs  
•
 
For  simple  apps:  
Silverlight
 
•
 
XML-­‐based  UI  declaraCon  +  C#  code  –  executed  in  .NET  CLR  
•
 
Vector  based  UI  widgets  
•
 
NavigaCon  framework,  event  based  input  
•
 
Basically,  Microso^’s  version  of  Flash  
•
 
For  games:  XNA  
•
 
C#  code  –  executed  in  .NET  CLR  
•
 
Direct3D  –  every  frame  is  redrawn  in  full  
•
 
Shaders
,  GPU  acceleraCon,  polling  based  input  
•
 
Basically,  same  as  in  
XBox
 
41  
This combination is very
similar to Android’s XML
and Java approach.
Games should translate
fairly well between the
XBox
and WP7 devices.
Developer  Tools  
•
 
Microso^  Windows  Phone  Developer  Tools  –  free  of  charge  
•
 
Basic  set  for  C#  developers  –  add-­‐on  for  Visual  Basic  developers  
•
 
Windows  7  required  
42  
CreaCng  the  UI  
43  
Binding  to  code  
44  
<Button Height="150” Width="300” Name="
FirstButton
” Content="Tap" />
private void
FirstButton_Click(object
sender,
RoutedEventArgs

e
)
{
if (
FirstButton.Content
as string == "Tap")
{

FirstButton.Content
= "Tap Again";
}
else
{

FirstButton.Content
= "Tap";
}
}
App  DistribuCon  
•
 
Windows  Phone  Marketplace  
•
 
$  99  /  year  registraCon  fee  
•
 
RelaCvely  few  apps  in  there  so  far  
•
 
Upload  procedure  straighEorward  from  Visual  Studio  
•
 
Microso^  does  cerCficaCon  tesCng  before  submi5ng  the  app  to  the  store  
•
 
Only  Microso^-­‐signed  apps  can  run  on  the  devices  
•
 
Microso^  is  heavy  on  
EULAs
 
•
 
When  you  use  a  WP7  device,  there  is  small  print  everywhere  
•
 
Similar  small  print  applies  to  any  app  submissions  –  Microso^  is  just  as  careful  
about  liCgaCon  as  Apple  
45  
46  
Brief  Comparison  
Food  for  thought  
Android
iOS

WP7
Symbian

Units sold in
2010
67 million
47 million
12 million
111 million
Device
Variants
Many
Some
None
Many
Easy if you
know…
Java
Objective C
C# or
Silverlight

Qt and C++,
or Java
Dev platform
Linux, Mac,
Windows
Mac
Windows
Linux, Mac,
Windows
Cost to
Develop
Free
Free
Free
Free
Cost to
distribute
Free
$99 / year
$99 / year
1 €
Competition
in app space
Fierce
Fierce and
controlled
Not much
Not much
47  
Units sold data: Gartner, Feb 2011
48