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201005 accelerometer and core Location


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201005 accelerometer and core Location

  1. 1. How to code for accelerometer and Core Location? Desert Code Camp Phoenix, Arizona 2010
  2. 2. Design Pattern 1.
  3. 3. Model(delegate) + Controller + View View Singleton Include XIB files Model Controller Delegates 3
  4. 4. Objective-C 2.
  5. 5. Objective-C   Is a simple computer language designed to enable sophisticated OO programming.   Extends the standard ANSI C language by providing syntax for defining classes, methods, and properties, as well as other constructs that promote dynamic extension of classes.   Based mostly on Smalltalk (class syntax and design), one of the first object-oriented programming languages.   Includes the traditional object-oriented concepts, such as encapsulation, inheritance, and polymorphism. 5
  6. 6. Files Extension Source Type .h Header files. Header files contain class, type, function, and constant declarations. .m Source files. This is the typical extension used for source files and can contain both Objective-C and C code. .mm Source files. A source file with this extension can contain C+ + code in addition to Objective-C and C code. This extension should be used only if you actually refer to C+ + classes or features from your Objective-C code. 6
  7. 7. #import   To include header files in your source code, you can use the standard #include, but….   Objective-C provides a better way #import. it makes sure that the same file is never included more than once.  #import  “MyAppDelegate.h”    #import  “MyViewController.h”    #import  <UIKit/UIKit.h>   7
  8. 8. Class   The specification of a class in Objective-C requires two distinct pieces: the interface (.h files) and the implementation (.m files).   The interface portion contains the class declaration and defines the instance variables and methods associated with the class. @interface    …    @end     The implementation portion contains the actual code for the methods of the class.  @implementation    …    @end   8
  9. 9. Class Class name @interface  MyClass  :  NSObject   Parent class {    int  count;    id  data;   Instance variables  NSString*  name;   }   -­‐  (id)initWithString:(NSString  *)aName;   methods +  (MyClass  *)createMyClassWithString:  (NSString  *)  aName;   @end   9
  10. 10. Class Class name @implementation  MyClass   -­‐  (id)initWithString:(NSString  *)  aName   {          if  (self  =  [super  init])  {                  count  =  0;                  data  =  nil;   methods                name  =  [aName  copy];                  return  self;          }   }   +  (MyClass  *)createMyClassWithString:  (NSString  *)  aName   {          return  [[[self  alloc]  initWithString:aName]  autorelease];   }   @end   10
  11. 11. Methods   A class in Objective-C can declare two types of methods:   Instance method is a method whose execution is scoped to a particular instance of the class. In other words, before you call an instance method, you must first create an instance of the class.   Class methods, by comparison, do not require you to create an instance. Method type identifier One or more signature keywords  -­‐(void)insertObject:(id)anObject  atIndex:(NSUInteger)index;   Return type Parameters with (type) and name 11
  12. 12. Methods So  the  declaration  of  the  method  insertObject  would  be:   -­‐(void)insertObject:(id)anObject  atIndex:(NSUInteger)index   Method type identifier, is (-) to instance methods, (+) to class methods. And  the  line  to  call  the  method  would  be:   [myArray  insertObject:anObj  atIndex:0];   12
  13. 13. Properties   They are simply a shorthand for defining methods (getters and setters) that access existing instance variables.   Properties do not create new instance variables in your class declaration.   Reduce the amount of redundant code you have to write. Because most accessor methods are implemented in similar ways   You specify the behavior you want using the property declaration and then synthesize actual getter and setter methods based on that declaration at compile time. 13
  14. 14. Properties In the interface we have: {   BOOL  flag;   NSString*  myObject;   UIView*  rootView;   }   @property  BOOL  flag;   @property  (copy)  NSString*  myObject;  //  Copy  the  object  during  assignement   @property  (readonly)  UIView*  rootView;  //  Create  only  a  getter  method.               …   And in the implementation side we have: @syntetize  flag;   @syntetize  myObject;   @syntetize  rootView;   …   myObject.flag  =  YES;   CGRect      viewFrame  =  myObject.rootView.frame;   14
  15. 15. Properties Writability   Readwrite. You can read/write it. This is the default value.   Readonly. You can only read it. Setter semantics (mutually exclusive)   Assign. Specifies that the setter uses simple assignment. This is the default value.   Retain. Specifies that a pointer should be retained.   Copy. Specifies that a copy of the object should be used for assignment. Atomicity (multithreading)   Nonatomic. Specifies that accessor methods are not atomic.   The default value is atomic but there is no need to specify it. 15
  16. 16. Protocols and Delegates   Protocols are not classes themselves. They simply define an interface that other objects are responsible for implementing   A protocol declares methods that can be implemented by any class.   In iPhone OS, protocols are used frequently to implement delegate objects. A delegate object is an object that acts on behalf of, or in coordination with, another object.   The declaration of a protocol looks similar to that of a class interface, with the exceptions that protocols do not have a parent class and they do not define instance variables.   In the case of many delegate protocols, adopting a protocol is simply a matter of implementing the methods defined by that protocol. There are some protocols that require you to state explicitly that you support the protocol, and protocols can specify both required and optional methods. 16
  17. 17. Example: Fraction Fraction.h   Fraction.m   #import  <Foundation/NSObject.h>     #import  "Fraction.h"     #import  <stdio.h>       @interface  Fraction:  NSObject  {              int  numerator;             @implementation  Fraction        int  denominator;      }       @synthesize  numerator;   //Properties  instead  of  getters  and     @synthesize  denominator;   //setters   @property  (nonatomic)  int  numerator;   //  Output  Print   @property  (nonatomic)  int  denominator;   -­‐(void)  print  {             printf("%i/%i",  numerator,denominator);     }       //Output  print   @end     -­‐(void)  print;     @end     17
  18. 18. Example: Fraction main.m #import <stdio.h> #import "Fraction.h" int main( int argc, const char *argv[] ) { Fraction *frac = [[Fraction alloc] init]; frac.numerator = 1; frac.denominator=3; printf( "The fraction is: " ); [frac print]; printf( "n" ); [frac release] return 0; } 18
  19. 19. Strings   The NSString class provides an object wrapper.   Supports storing arbitrary-length strings, support for Unicode, printf-style formatting utilities, and more.   Shorthand notation for creating NSString objects from constant values. Precede a normal, double-quoted string with the @ symbol. NSString*    myString  =  @”Hello  Worldn";   NSString*    anotherString  =                  [NSString  stringWithFormat:@"%d  %s",  1,  @"String”];   19
  20. 20. Let us code: Autorotate and Accelerometer 3
  21. 21. Accelerometer Measure of Gravity acceleration: 0g 1g 2.3g 21
  22. 22. Reading the Accelerometer   UIAccelerometer object in UIKit allow you to access to the raw accelerometer data directly. This object reports the current accelerometer values.   To get an instance of this class, call the sharedAccelerometer method of UIAccelerometer class.   The updateInterval property define the reporting interval in seconds. -­‐(void)viewDidLoad  {      UIAccelerometer  *accelerometer  =  [UIAccelerometer  sharedAccelerometer];      accelerometer.delegate  =  self;      accelerometer.updateInterval  =    1.0/60;      [super  viewDidLoad];   }   22
  23. 23. Reading the Accelerometer   A delegate (UIAccelerometerDelegate) will receive acceleration events. @interface  FooViewController:  UIViewController  <UIAccelerometerDelegate>     Use accelerometer:didAccelerate: method to process accelerometer data. -­‐(void)accelerometer:(UIAccelerometer  *)accelerometer  didAccelerate:  (UIAcceleration  *)acceleration  {              NSString  *s  =  [[NSString  alloc]  initWithFormat:@"%f,  %f,  %f",        acceleration.x,  acceleration.y,  acceleration.z];    accLabel.text  =  s;      [s  release];   } 23
  24. 24. AutoRotate The UIViewController class provides the infrastructure needed to rotate your interface and adjust the position of views automatically in response to orientation changes. -(BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation interfaceOrientation { return YES; //return (interfaceOrientation == UIInterfaceOrientationPortrait); } interfaceOrientation values:   UIInterfaceOrientationPortrait   UIInterfaceOrientationPortraitUpsideDown   UIInterfaceOrientationLandscapeLeft   UIInterfaceOrientationLandscapeRight 24
  25. 25. AutoRotate adjustments 25
  26. 26. Core Location 4
  27. 27. Core Location The Core Location framework monitors signals coming from cell phone towers and Wi-Fi hotspots and uses them to triangulate the user's current position. 27
  28. 28. Getting the User's Current Location   Create an instance of CLLocationManager class. It  is  necessary  to  include  the  CoreLocation.framework   #import  <CoreLocation/CoreLocation.h>   @interface  FooViewController:  UIViewController<CLLocationManagerDelegate>       To begin receiving notifications, assign a delegate and call the startUpdatingLocation method. -­‐(void)viewDidLoad  {      CLLocationManager  *locationManager=  [[CLLocationManager  alloc]  init];      [locationManager  startUpdatingLocation];locationManager.delegate  =  self;      locationManager.distanceFilter  =  kCLDistanceFilterNone;            locationManager.desiredAccuracy  =  kCLLocationAccuracyBest;   }   28
  29. 29. Using the Core Location   We need implement this: -­‐  (void)locationManager:(CLLocationManager  *)manager  didUpdateToLocation: (CLLocation  *)newLocation  fromLocation:(CLLocation  *)oldLocation  {      NSString  *latitudeString  =  [[NSString  alloc]  initWithFormat:@"%g°",          newLocation.coordinate.latitude];      latitudeLabel.text  =  latitudeString;      [latitudeString  release];    NSString  *longitudeString  =  [[NSString  alloc]  initWithFormat:@"%g°",          newLocation.coordinate.longitude];      longitudeLabel.text  =  longitudeString;      [longitudeString  release];   }   29
  30. 30. Exercises and References 5
  31. 31. iPhone Dev Center 31