iPhone Programming

1
iPhone Programming

• Version 2
• Created by Nathan Magnus

2
Apple

• Your most useful resource is the Apple developer
  documentation.
• http//developer.apple.com/

3
Xcode IDE

• Apple provides an IDE for creating iPhone
  applications
• Xcode can also be used to create OSX applications

4
Xcode IDE

• Installation
• Download from http//developer.apple.com/iphone/in
  dex.action
• You will need to create an account if you do not
  already have one
• Mount by clicking on it in the download directory
• Double click on iPhone SDK

5
iPhone Simulator

• Simulates an iPhone.
• Can be rotated by 90 to the right or left
  through the Hardware menu
• Supports multiple touches (option and
  option-shift)
• Known bugs
• Cannot be rotated upside down
• When rotated there is a small area that will not
  respond to touches

6
An IPhone Application

• Create an application that loads Google in a
  UIWebView
• The user enters a URL into the text field and
  when they click enter on the keyboard the
  UIWebView loads that address

7
Creating the Program

• Create a new View-Based application in Xcode
• File -gt New Project...
• Select View-Based Application and click
  Choose...
• Name your project webNav and save

8
Program 1

• In the upper pane, double click on
  webNavViewController.xib
• This will open the interface builder (IB)

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Program 1

• Ensure the Library window is open (Tools-gt
  Library)

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Program 1

• Under Data View drag and drop a Web View onto
  the main view

11
Program 1
12
Program 1

• Click on webNavViewController.h in Xcode

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Program 1

• Add the following lines of code
• Under _at_interface webNavViewController
  UIViewController
• Add IBOutlet UIWebView webView
• Under before _at_end
• Add _at_property (nonatomic, retain) UIWebView
  webView

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Program 1

• Return to the Interface Builder
• Click on the WebView in the main View

15
Program 1

• Ensure that the Connections Inspector is open
  (Tools -gt Connections Inspector)

16
Program 1

• Click on the circle beside New Referencing
  Outlet and drag to Files Owner

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Program 1

• Select webView from the two options

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Program 1

• Save the Interface Builder
• Double Click on webNavViewcontroller.m

19
Program 1

• Uncomment -(void)viewDidLoad function

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Program 1

• Under super viewDidLoad
• Create a NSURL
• NSURL url NSURL URLWithString_at_http//www.goo
  gle.ca
• The _at_ makes the following string a NSString
• Create a NSURLRequest
• NSURLRequest request NSURLRequest
  requestwithURLurl
• Load the request
• webView loadRequestrequest

21
Program 1
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Program 1

• This is what the program should look like

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Information

• Files (.m files can be renamed to .mm to allow
  Objective-C)
• ProjectNameAppDelegate (.h and .m) - Creates the
  window and view
• ProjectNameViewController (.h and .m) - Controls
  user interaction with the view
• viewDidLoad is called when the initial view loads

24
Program 2

• Create an application that has a UITextField,
  UILabel, UIButton and UIImageView
• Screen begins with an image of a your
  handsome/beautiful instructor (or a hated
  celebrity), a UITextField and a UIButton (with an
  appropriate title)
• The user enters a phrase into a UITextField.
  After they are done editing they can click on a
  UIButton.
• If the phrase they entered matches a certain
  phrase then the image changes to an explosion and
  a label appears telling the user they just blew
  up the instructor.
• If the phrase does not match, a message telling
  them to try again should be displayed.

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Program 2

• Steps
• Find an image of your handsome/beautiful
  instructor or a hated celebrity and save it to
  Documents
• Find an image of an explosion and save it to
  Documents
• Create a new View-Based Application (call it
  Boom
• Create the Interface using IB
• Add a UILabel (found in Inputs Values)
• Add a UIImageView (found in Data Views)
• Add a UITextField (found in Inputs Values)
• Top half of screen due to onscreen keyboard
• Add a UIButton (found in Inputs Values)

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Program 2
27
Program 2

• Click on the Attributes Inspector tab (or
  Tools-gtAttributes Inspector)

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Program 2

• Select the button and add the title Check Input

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Program 2

• Navigate to your saved image using Finder
• Drag and drop your images into the Resources
  group of the Xcode project

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Program 2

• Select Copy items into destination groups
  folder (if needed) and ensure other settings are
  all defaults then click Add

31
Program 2
32
Program 2

• Click on the UIImageView in the IB and add your
  image in the Attributes Inspector

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Program 2

• Open the Connection Inspector
• (Tools-gtConnections Inspector)
• Select each object on the interface builder
  (UITextField, UIButton, UIImageView, UILabel),
  drag to Files Owner and select the appropriate
  option
• For the UITextField, click on the circle beside
  delegate and drag to Files Owner

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Program 2
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Program 2

• Add to BoomViewController.h
• After _at_interface BoomViewController
  UIViewController
• IBOutlet UILabel label
• IBOutlet UITextField input
• IBOutlet UIImageView image
• IBOutlet UIButton button

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Program 2

• After before _at_end
• _at_property (nonatomic, retain) UILabel label
• _at_property (nonatomic, retain) UITextField input
• _at_property (nonatomic, retain) UIImageView image
• _at_property (nonatomic, retain) UIButton button
• -(BOOL)textFieldShouldReturn (UITextField)theTex
  tField
• -(void)checkInput

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Program 2
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Program 2

• In BoomViewController.m
• Uncomment the (void)viewDidLoad method
• Add after super viewDidLoad
• label setText_at_Enter the detonation code.
• button addTargetself action_at_selector(checkInput
  ) forcontrolEventsUIControlEventTouchUpInside

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Program 2
40
Program 2

• Add after the (void)viewDidLoad function
• -(BOOL)textFieldShouldReturn (UITextField)theTex
  tField
• theTextField resignFirstResponder
• return YES

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Program 2
42
Program 2

• Add after the -(void)viewDidLoad method
• -(void)checkInput
• NSString userInput input text
• if(userInput compare_at_Boom! NSOrderedSame)
• label setText_at_Your instructor went BOOM!
• image setImageUIImage imageNamed_at_explosion.
  jpg
• else
• label setTextNSString stringWithCStringThat
  is not the correct detonation code.
• image setImageUIImage imageNamed_at_nathan.jpg
  

43
Program 2
44
Program 2

• Finished Product

45
Program 2
46
NSArray

• Used to hold objects in an array
• id is the default object type. All objects
  (NSUInteger, NSString, etc) can be passed as an
  id
• Initializing
• (id)arrayWithObjects(id)obj1, (id)obj2,,nil -
  nil terminated list of objects to be added to the
  array
• Accessing
• -(id)objectAtIndex(NSUInteger)index - return the
  id of the object at the given index
• Functions also exist for sorting, comparing and
  obtaining information about the array

47
Objective-C

• Variables
• Types include char, int, unsigned, float, double,
  BOOL
• Constants declared using const keyword
• declared by type name
• Ex) float floatVal char character
• Conditional structures
• if(condition) code
• else if(condition) code
• else (condition) code
• switch (condition)
• case constant code
• break
• default
• break

Comparison Operators
Equal
lt Less or Equal
gt Greater or Equal
lt Less
gt Greater
! Not Equal
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Objective-C

• Loops
• do code while(condition)
• while(condition) code
• for(initialize condition increment) code
• Arrays
• Declaration
• type namesizeOfArray
• Initialize
• type name value1, value2
• name0value1 name1value2
• Pointers
• Objects when using Object method must be
  pointers or class name
• Initialize
• type name
• nil/null - indicates no object at pointer but if
  used will not cause crash

49
Example of Objective-C

• -(void)method
• const unsigned loopAmt 10
• printf("Testing ")
• for(unsigned i0 iltloopAmt i)
• printf("i...", i)
• //prints Testing0123456789

50
Exercise

• 1) Create a web navigation application with
  UITextField and UIWebView
• The user enters a URL into the text field and
  when they click enter on the keyboard the
  UIWebView loads that address
• 2) Create a simple game of Tic Tac Toe
• Different status messages should be displayed on
  the screen (most likely using a UILabel)
• When a game ends, nothing can be pushed except a
  button that asks if the user would like to play
  again

51
Objective-C Classes

• Interface declared by _at_interface
  ClassNameSuperClass and ended by _at_end
• SuperClass must always be Object or a subclass
  of Object (NSObject for the iPhone)
• Implementation declared by _at_implementation
  ClassName
• All class methods are public
• Instance variables are private by default
• Classes can be extended with categories (no
  example will be given)

52
Example of Classes

• //tempClass inherits from NSObject
• _at_interface tempClass NSObject
• _at_private
• int var //private instance variable
• //function prototypes
• (int)staticMethod
• -(int)method
• _at_end //end of interface

53
Example of Classes

• _at_implementation tempClass
• (int)staticMethod
• var 200
• return var
• -(int)method
• var 100 //assign a value to var
• return var //return value of var
• _at_end

54
Objects

• Since every object must extend the NSObject class
  (or a subclass of it) to create a new object call
  the alloc method
• Ex) tempClass tc tempClass alloc
• If a method is static, it can be called without
  allocating the object
• Ex) tempClass staticMethod

55
Objective-C

• Syntax almost identical to Objective-C
• Allows the use of C libraries and functions
  (ie ltiostreamgt, ltfstreamgt)
• .h extension for header files and .mm extension
  for implementation files

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Example of Objective-C

• include ltiostreamgt
• -(int)getInteger
• return 5
• int aFunction(id this2)
• /print the value returned by the getInteger
  function of the object passed to the method/
• cout ltlt this2 getInteger
• return 10

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Info.plst

• Info.plst file contains information about your
  project
• Application icon (must be included as a resource)
• Main nib file

58
NSString

• Full list of functions and properties can be
  found at http//developer.apple.com/documentati
  on/Cocoa/Reference/Foundation/Classes/NSString_Cla
  ss/Reference/NSString.html
• Creating
• Add _at_ in front of a regular string
• ex) _at_Hello World!
• NSString stringWithCStringHello World!
• Many other methods including from file and URL
• Methods
• length, lowercaseString, uppercaseString,
  capitalizedString, compare(NSString)aString
• NSOrderedAscending, NSOrderedSame,
  NSOrderedDescending

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Common Information

• hidden - whether the object is visible or not
• Ex) label.hidden NO
• userInteractionEnabled - whether the object will
  respond to a touch or not
• Ex) label.userInteractionEnabled YES
• center - CGPoint representing the center of the
  object (CGPoint is a struct with x and y fields)
• Ex) cout ltlt label.center.x

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UIButton

• Found in IB library under Inputs Values
• Setters
• setBackgroundImage(UIImage) forState(UIControlS
  tate)
• setImage(UIImage) forState(UIControlState)
• setTitle(NSString) forState(UIControlState)
• Properties
• currentTitle, currentTitleColor, currentImage,
  currentBackgroundImage, hidden
• Ex) aButton.hidden YES

61
UIImageView

• Found in IB library under Data Views
• Initializers
• initWithImage(UIImage)
• UIImage imageNamed(NSString)name is useful
• Properties
• image, userInteractionEnabled, hidden

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UITextView

• Found in IB library under Data Views
• UITextAlignment - UITextAlignmentRight,
  UITextAlignmentLeft, UITextAlignmentCenter.
• UIColor allows allows for creation of custom
  colors as well as presets such as greyColor,
  redColor, greenColor, etc
• Properties
• text, font, textColor, editable, textAlignment,
  hidden

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UITextField

• Found in IB library under Inputs Values
• Properties
• text, font, textColor, textAlignment, hidden

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Closing the Keyboard

• Keyboard automatically displays on the lower half
  of the screen when a field that allows input is
  touched
• Keyboard does not automatically close
• Must set the delegate (via the IB connection
  manager window) for the textView, textField or
  other object that brings up the keyboard to
  Files Owner
• //when return is touched on the keyboard, this is
  called (BOOL)textFieldShouldReturn
  (UITextField)theTextField
• theTextField resignFirstResponder
• return YES

65
UILabel

• Found in IB library under Inputs Values
• Properties
• text, font, textColor, textAlignment, enabled,
  adjustsFontSizeToFitWidth, minimumFontSize,
  numberOfLines, highlightedTextColor, hidden

66
NSURL/NSURLRequest

• NSURL Functions
• URLWithString(NSString)string
• initWithString(NSString)string
• URLWithString(NSString)string
  relativeToURL(NSURL)url
• initWithString(NSString)string
  relativeToURL(NSURL)url
• NSURLRequest Functions
• initWithURL(NSURL)url

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UIWebView

• Found in IB library under Data Views
• Properties
• canGoBack, canGoForward, loading
• Methods
• goBack, goForward, stopLoading, reload,
  loadRequest(NSURLRequest)request

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Creation Without IB

• All UI Objects can be created without using the
  IB
• Create a CGRect variable to hold the object using
  CGRectMake(x-offset, y-offset, width, height)
• Ex) CGRect r CGRectMake(20.0, 20.0, 100.0,
  40.0)
• Allocate the memory for and initialize the object
  using initWithFrame
• Ex) UILabel label UILabel alloc
  initWithFramer
• Set object specific properties
• Ex) label setText_at_Label Created
• Add to the appropriate view
• Ex) self addSubviewlabel

69
Selectors

• Selectors are written into a table and used at
  runtime to reference a method
• Class methods and instance methods with the same
  name would be assigned the same selector
• The _at_selector() directive allows the programmer
  to refer to a compiled selector rather than
  method name
• To define a selector use SEL
• Ex) SEL aSelector _at_selector(toSelect)
• Other methods can be used to get selector
  information
• NSSelectorFromString(NSString)
• NSStringFromSelector(SEL)

70
Selectors

• Methods that use Selectors
• performSelector(SEL)
• performSelector(SEL) withObject(id)
• performSelector(SEL) withObject(id)
  withObject(id)

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Selector Example

• -(void)method2(int)i int2(int)j
• //outputs 12 to the debug console
• cout ltlt i intValue ltlt j intValue
• -(void)method
• NSNumber i NSNumber numberWithInt1
• NSNumber j NSNumber numberWithInt2
• SEL s _at_selector(method2int2)
• self performSelectors withObjecti
  withObjectj
• //outputs method2int2 to debug console
• cout ltlt NSStringFromSelector(s) cString

72
Add a Target Method

• Can add an action to a UI object when it is
  touched
• backButton addTargetwebView action_at_selector(goB
  ack) forControlEventsUIControlEventTouchUpInside
  

73
Multiple Views with IB

• Multiple views in Interface Builder can be
  displayed and hidden by their hidden property
• Multiple windows can be displayed and hidden by
  their hidden property

74
Touches

• Four functions can be overwritten (in EAGLView or
  ProjectNameViewController)
• -(void)touchesBegan(NSSet)touches
  withEvent(UIEvent)event - Called when finger(s)
  touch the display
• -(void)touchesMoved(NSSet)touches
  withEvent(UIEvent)event - Called when finger(s)
  are moved on the display
• -(void)touchesEnded(NSSet)touches
  withEvent(UIEvent)event - Called when
  fingers(s) are removed from the display
• -(void)touchesCancelled(NSSet)touches
  withEvent(UIEvent)event - Called if the system
  interrupts your application

75
Using Touches

• In order for information about multiple touches
  to be passed, must set self.multipleTouchEnabled
  YES
• The functions parameters can be used to get
  information about the touches
• touches allObjects objectAtIndex0 - will
  return the id of the first touch on the display.
• This id can be used to call the
  locationInViewself function which returns a
  CGPoint struct (holds x and y coordinates)

76
Example of Multiple Touches

• -(void) touchesEnded(NSSet)touches
  withEvent(UIEvent)event
• CGPoint touch
• int touchCount event allTouches count
• self.multipleTouchEnabled YES
• for(int i0 ilttouchCount i)
• touch touches allObjectsobjectAtIndexi
  locationInViewself
• printf("Touch i at (f,f)\n", i1, touch.x,
  touch.y)

77
Orientation

• iPhone has built in accelerometer that can be
  used to determine orientation
• Need to turn orientation notifications on
• UIDevice currentDevice beginGeneratingDeviceOri
  entationNotifications
• Can access by accessing UIDevice
  currentDevice.orientation
• 0 represents state unknown (UIDeviceOrientationUnk
  nown)
• 1 represent upright state in simulator
  (UIDeviceOrientationPortrait)
• 3 represents landscape view with left side down
  (UIDeviceOrientationLandscapeLeft)
• 4 represents landscape view with right side down
  (UIDeviceOrientationLandscapeRight)

78
Exercise

• Create a program that draws 2 shapes. These
  shapes will move toward the new bottom of the
  screen if it is rotated.

79
Exercise

• Create a program that draws a textured shape in
  the middle of the screen
• If two fingers are moved in parallel the image
  moves in the direction of the fingers movement
• If two fingers move apart or towards each other
  the shape is enlarged or shrunk

80
Exercise

• Create a program that draws a shape. Every 0.2
  seconds the object moves to right, left, up or
  down.
• Use touch events to control the direction that
  the object moves

81
OpenGL ES Application

• Draw, rotate and move shapes
• Change colors and sizes at run-time
• Files (.m files can be renamed to .mm to allow
  Objective-C)
• EAGLView (.h and .m) - Already imports OpenGL ES
  library
• -(void)drawView - is called every
  animationInterval seconds
• Other Functions already given include
  startAnimation, stopAnimation, setAnimationInterva
  l, setAnimationTimer, dealloc, createFramebuffer,
  destroyFramebuffer and initWithCoder
• ProjectNameAppDelegate (.h and .m) - Creates the
  window and view

82
NSTimer

• Useful class that is frequently used to call a
  method periodically based on time
• Methods
• NSTimer scheduledTimerWithTimeInterval(float
  seconds) target(id target) selector_at_selector(met
  hod name) userInfonil repeats(YES or NO)

83
OpenGL ES

• Some important OpenGL ES functions
• glEnable(capability) and glDisable(capability) -
  enable or disable the capabilities declared by a
  constant
• GL_TEXTURE_2D - allow textures to be mapped to 2D
  objects
• GL_LIGHTING - allow lighting to modify colors
• GL_FOG - blend a fog color into the post
  texturing color
• GL_BLEND - allows for transparency

84
OpenGL ES

• glClientEnableState(capability) and
  glClientDisableState(capability) - enable and
  disable a capability
• GL_VERTEX_POINTER - vertices of an object are
  defined by an array of points
• GL_COLOR_POINTER - colors at vertices are defined
  by an array of points
• GL_TEXTURE_COORD_POINTER - map texture
  coordinates in an array to the texture

85
OpenGL ES

• glTranslatef(x, y, z) - move the object on the
  coordinate plane by x, y and z
• glRotatef(x, y, z) - rotate the object around the
  line defined by x, y and z
• glDrawArrays(mode, first, count)
• mode - the way to draw the object
• GL_TRIANGLE_FAN, GL_TRIANGLE_STRIP, GL_LINE_LOOP,
  GL_LINES
• first - the element in the array that represents
  the first point
• count - the number of points in the array

86
OpenGL ES

• glBlendFunc(sfactor, dfactor)
• sfactor - specifies how RGBA source blending
  computed (use GL_SRC_ALPHA)
• dfactor - specifies how RGBA destination blending
  computed (use GL_ONE_MINUS_SRC_ALPHA)
• glTexEnvf(target, pname, param) /
  glTexEnvi(target,pname,param)
• target - specifies the texture environment
  (GL_TEXTURE_ENV)
• pname - single valued texture environment
  parameter (GL_TEXTURE_ENV_MODE)
• param - symbolic constant (GL_DECAL)

87
OpenGL ES

• glVertexPointer(dimensions, type, stride,
  vertexPointer)
• glColorPointer(values, type, stride,
  colorPointer)
• glColor4f(red, green, blue, alpha) /
  glColor4ub(red, green, blue, alpha)
• glTexCoordPointer(dimensions, type,
  texturePointer)
• glBindTexture(type, texture)

88
OpenGL ES

• glMatrixMode(type) - the type of view being
  worked with
• GL_MODELVIEW - Position of the model relative to
  the screen
• GL_PROJECTION - View seen on the screen
• glPushMatrix() - save the current view to a stack
  
• glPopMatrix() - retrieve the last view that was
  pushed onto the stack
• glLoadIdentity() - replaces the current matrix
  with the identity matrix (resets to defaults)

89
OpenGL ES

• glOrthof(xMin, xMax, yMin, yMax, zMin, zMax) -
  set up the coordinate plan
• xMin - the lowest x value visible
• xMax - the highest x value visible
• yMin - the lowest y value visible
• yMax - the highest y value visible
• zMin - the lowest z value visible
• zMax - the highest z value visible

90
Load Textures

• -(void)loadTexture(NSString )name
  intoLocation(GLuint)location
• CGImageRef textureImage UIImage
  imageNamedname.CGImage
• if (textureImage nil) //If the image
  doesnt exist, print an error
• NSLog(_at_"Failed to load texture image")
• return
• NSInteger texWidth CGImageGetWidth(textureImage
  ) //get the width
• NSInteger texHeight CGImageGetHeight(textureIma
  ge) //get the height
• GLubyte textureData (GLubyte
  )malloc(texWidth texHeight 4)
• CGContextRef textureContext
  CGBitmapContextCreate(textureData,texWidth,
  texHeight,8, texWidth 4, CGImageGetColorSpace
  (textureImage), kCGImageAlphaPremultipliedLast)
• CGContextTranslateCTM(textureContext, 0,
  texHeight)
• CGContextScaleCTM(textureContext, 1.0, -1.0)
• CGContextDrawImage(textureContext,
  CGRectMake(0.0, 0.0, (float)texWidth,
  (float)texHeight), textureImage)
• CGContextRelease(textureContext)
• glBindTexture(GL_TEXTURE_2D, location)
• glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,
  texWidth, texHeight, 0, GL_RGBA,
  GL_UNSIGNED_BYTE, textureData)
• free(textureData)
• glTexParameterf(GL_TEXTURE_2D,
  GL_TEXTURE_MIN_FILTER, GL_LINEAR)
• glTexParameterf(GL_TEXTURE_2D,
  GL_TEXTURE_MAG_FILTER, GL_LINEAR)

91
glScale

• glScalef(GLfloat x, GLfloat y, GLfloat x)
• glScaled(GLdouble x, GLdouble y, GLdouble z)
• Scale the current view matrix by x, y and z

92
Example

• float vertices
• 1, 1,
• 1, 0,
• 0, 0,
• 0, 1
• glEnable(GL_BLEND)
• glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
  
• glMatrixMode(GL_MODELVIEW)
• glPushMatrix()
• glTranslatef(5, 5, 0)
• glScalef(0.5, 0.5, 0)
• glVertexPointer(2, GL_FLOAT, 0, vertices)
• glEnableClientState(GL_VERTEX_ARRAY)
• glColor4ub(255, 255,51, 128)
• glDrawArrays(GL_TRIANGLE_STRIP, 0, 6)
• glPopMatrix()
• glDisable(GL_BLEND)

93
Exercise

• Create an application that draws 2 shapes which
  will bounce off the sides of the screen and each
  other. Add a texture and vector physics to this
  shape if you need more of a challenge.
• Create an application that draws stars in the top
  half of the screen.
• Each star has a random rotation and location on
  the screen. The star will change a combination of
  size, color, transparency or rotation
  periodically to simulate twinkling.

94
Memory Management

• If instance created by Object alloc message or
  malloc(size) C function it will not be
  automatically released. Each of these calls (as
  well as every time retain is called) increments
  the retain count.
• Methods of releasing data (releasing the object
  reduces its retain count)
• release ObjectVariable release
• autorelease - ObjectVariable autorelease (if
  makes retain count 0, ensures object is not going
  to be referenced. Generally object is released at
  end of function/current scope)
• dealloc() is called when objects retain count is
  0 (similar to C destructor)
• Release all appropriate instance variables in
  dealloc

95
Objective-C Classes

• Interface declared by _at_interface
  ClassNameSuperClass and ended by _at_end
• SuperClass must always be Object or a subclass
  of Object (NSObject for the iPhone)
• Implementation declared by _at_implementation
  ClassName
• All class methods are public
• Instance variables are private by default
• Classes can be extended with categories (example
  later)

96
Objective-C

• Used as default language in xcode
• Can run almost all c programs
• .h extension for header files and .m extension
  for implementation files
• Methods in same class referenced using self
  (similar to the this keyword in c)
• Syntax
• Default return type is id
• Message Object functionarg1 parameter2arg2
  (similar to Object-gtfunction(arg1, arg2))
• -(returnType)function(type)arg1
  parameter2(type)arg2 code
• (returnType)staticFunction(type)arg1
  parameter2(type)arg2 code

97
Extending Classes

• // A class extension
• _at_interface tempClass (Category)
• // New methods
• (BOOL) tOrF
• (void) doSomething
• _at_end
• _at_implementation tempClass(Category)
• (BOOL) tOrF
• (void) doSomething
• _at_end

98
Creating an iPhone Project

• File-gtNew Project
• Options we will discuss
• OpenGL ES Application
• View-Based Application
• Tab Bar Application

99
Example of Objective-C

• - (void)viewDidLoad
• super viewDidLoad
• self fnWithInt

100
Objective-C

• -(void)fnWithInt(int)i int2(int)j
• Method name - fnWithIntint2
• C can call Objective-C functions and Objective-C
  can call C functions.
• self can not be used from C functions
• Work around this by creating a global variable or
  passing type id

101
Objective-C Called by C

• -(int)getInteger
• return 5
• int aFunction(id this2)
• /print the value returned by the getInteger
  function of the object passed to the method/
• printf("i", this2 getInteger)
• return 10

102
Concepts/Directives

• _at_synthesize - used to automatically create
  missing getters (cd) and setters (setCd)
  function for an instance variable
• Synthesized variables must have an associated
  _at_property
• ex) _at_property (retain) UIDevice cd
• //creates 2 methods cd and setCd(UIDevice)n
  ewDevice
• _at_synthesize cd
• //set cd to the current device using the
  synthesized method
• self setCdUIDevice currentDevice

103
_at_property

• _at_property (parameters) type name
• nonatomic - allows more than one thread to access
  a getter/setter at a time
• atomic - only allow one thread to access a
  getter/setter at a time (default)
• retain - setter should use retain in the
  variable assignment
• (ex var1 var2 retain)
• Used for objects
• assign - setter will assign directly to the
  variable
• Used for basic variable types
• readonly - setter will not be generated