About ObjectsUIView Subclass of UIResponder UIResponder deﬁnes behavior for classes that can...

About Objects

Introduction to iPhone ProgrammingSECTION 2

Developer–oriented training.

www.AboutObjects.com

Friday, October 9, 2009

Overview

What is iPhone SDK?

Layered libraries and frameworks

Development tools

Documentation

Mobile Platform

Resource constrained environment

Memory

Graphics

Battery

Smaller API footprint

Requires extra attention to details like memory management, etc.

iPhone SDK

Core OS

Cocoa Touch

Core Services

Core Foundation C Library Strings, dates, collections, threads, etc.

Address Book Framework Managing contact info

CFNetwork C Library Low-level network access

Core Location Framework Accessing geospatial positioning info

Security Framework Manages certificates, public/private keys, etc.

SQLite C Library Accessing lightweight SQL database

XML Support ObjC Class NSXMLParser class

iPhone SDK

Core OS

Cocoa Touch

Core Services

Open GL ES

Core Graphics

Core Animation

Core Audio

iPhone SDK

Cocoa Touch

Core OS

Core Services

Cocoa Touch

Foundation Framework

Wrappers for strings, numbers, dates, binary data

Collection classes (arrays, sets, dictionaries, etc.)

Bundles (dynamically loadable app modules)

User preferences

Threads and run loops

Files, streams and URLs

Bonjour (dynamic discovery)

Application management and integration (via URL schemes)

Graphics and windowing

Handling touch events

User interface views and controls

Text handling

Web content

Device-specific features (accelerometer, camera, photo library)

IDE for iPhone Projects

Run (Simulator, device)

Source code management (SCM)

Documentation

Interface Builder

GUI design tool

Doesn't generate code

Works with ‘Freeze-dried’ objects

Archived in .nib files

Dynamically loaded

Objects deserialized at load time

IB Learning Approach

Start coding using mostly APIs

Migrate to IB when we have solid grounding at the API level

Xcode IDE and Interface Builder (IB)

Located in /Developer/Applications

Drag icons to dock to keep them handy

To create a new project

1. Select File > New Project... from the menu

2. Select iPhone OS | Application in left pane

3. Choose Window-Based Application project template

4. Save as HelloWorld

Configuring XcodeAll-In-One Layout

Temporarily close project

Go to Xcode > Preferences

General pane

Select All-In-One from Layout dropdown

Building and Running

Debugging pane

Select Show Console & Debugger from On Start dropdown

Xcode Groups & Files

Groups are logical groupings of files

Don't map to folder structure

By default all sources in top-level directory

You can manually map individual groups to subfolders

File references are also logical

Add/Delete = add/delete files from build

main.m

main() function

Defined in main.m

UIApplicationMain()UIApplication singleton

Starts program's main event loop

int main(int argc, char *argv[]){ NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; int val = UIApplicationMain(argc, argv, nil, nil); [pool release]; return val;}

MainWindow.xibInterface Builder file in XML format

Compiled into .nib (NeXT Interface Builder) file

<?xml version="1.0" encoding="UTF-8"?><archive type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="7.02"> <data> ... <object class="NSMutableArray" key="IBDocument.RootObjects" id="1000"> <bool key="EncodedWithXMLCoder">YES</bool> <object class="IBProxyObject" id="372490531"> <string key="IBProxiedObjectIdentifier">IBFilesOwner</string> </object> ... <object class="IBUITableView" id="685065310"> <nil key="NSNextResponder"/> <int key="NSvFlags">274</int> <string key="NSFrameSize">{320, 480}</string> <bool key="IBUIOpaque">NO</bool> ... </object> </object>

info.plist

Config info for UIApplicationMain()App id (namespace for app)

Name displayed in UI

App icon

App version

Name of main nib file

Name of principal class (allows you to subclass UIApplication)

<key>CFBundleIdentifier</key><string>com.aboutobjects.lab.*</string>

<key>CFBundleDisplayName</key><string>My App</string>

<key>CFBundleIconFile</key><string>myicon.png</string>

<key>CFBundleVersion</key><string>1.17</string>

<key>NSMainNibFile</key><string>MainWindow.xib</string>

<key>NSPrincipalClass</key><string>UIApplication</string>

Plist Editor

Plus icon for new rows

Drop down for keys

To view as XML

Right-click in Groups and Files

Select Open As... > Source Code File

To switch back

Right-click in Groups and Files

Open As... > XML Property List

Document Browser

API docs

Guides

Browse Mode

Bookmarks

First Application

Programmatic vs. IB

To create a Nibless project:

1. Remove MainWindow.xib

2. Delete nib file name in info.plist

3. Pass name of app delegate to UIApplicationMain in main.m

4. Create the app's main window in your app delegate class

UIApplication Class

Obtaining an instance

+ sharedApplication

Properties

window

keyWindow

delegate

StatusBar Orientation and Style

- setStatusBarOrientation:animated:

- setStatusBarStyle:animated:

- setStatusBarHidden:animated:

The main() Routine

#import <UIKit/UIKit.h>

int main(int argc, char *argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; int retVal = UIApplicationMain(argc, argv, nil, nil); [pool release]; return retVal;}

What is a Delegate?

Common design pattern in Cocoa and Cocoa Touch.

Lets you customize behavior of framework classes without subclassing.

Certain key framework classes (such as UIApplication, UITableView, etc.) declare a property named delegate.

You can set this property to point to an instance of any class that implements one or more methods of corresponding delegate protocol

Instance then becomes target for these run-time messages

Your implementation of these methods can do whatever you like

Application Delegate

Implements UIApplicationDelegate Protocol

All methods optional

UIApplication calls delegate methods to notify of significant application-wide events

App launch and termination

Memory warnings

Changes in orientation

Becoming the active application and being deactivated

Also provides implementation for opening URLs

Startup Sequence

instantiate

setDelegate:

applicationDidFinishLaunching:

UIApplicationMain

(C function) UIApplication AppDelegate

Registering Your App Delegate

App delegate can be (and often is) registered in the .nib file

To register programmatically:

#import <UIKit/UIKit.h>

int main(int argc, char *argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; int retVal = UIApplicationMain(argc, argv, nil, @"MyAppDelegate"); [pool release]; return retVal;}

Implementing Delegate Methods

did... and will... delegate methods simply notify delegate of events

should... methods allow delegate to alter behavior

- (void)applicationDidFinishLaunching:(UIApplication *)application{ CGRect frameRect = [[UIScreen mainScreen] bounds]; UIWindow *myWindow = [[UIWindow alloc] initWithFrame:frameRect]; [self setWindow:myWindow]; [myWindow release]; ...}

- (void)applicationWillTerminate:(UIApplication *)application{ // Persist application state ...}

UIView

Subclass of UIResponder

UIResponder defines behavior for classes that can respond to events

View Hierarchy

UIView defines subviews property (NSArray)

Methods to manage drawing, hit testing, etc.

Responsibilities

Drawing

Animation

Responding to events (touches, etc.)

View Hierarchy

UIView Behavior

Defines rectangular area for drawing

Implements drawing behavior

Maintains list of subviews

Tracks whether needs redisplay

Converts coordinates

Manages scrolling

Manages layers

Provides animation

Properties Methods

backgroundColor initWithFrame:

opaque addSubview

frame drawRect:

bounds exchangeSubviewAtIndex:

center hitTest:withEvent:

hidden insertSubview:atIndex:

subviews layoutIfNeeded

superview sendSubviewToBack:

tag setNeedsDisplay

layer setNeedsDisplayInRect:

transform sizeToFit

userInteractionEnabled viewWithTag:

autoresizesSubviews removeFromSuperview:

View Geometry

UIView class

Defines a rectangular drawing area

Provides built-in drawing behavior

Each view maintains its own local coordinates

Frame and Bounds rectangle

Frame is a computed value based on bounds and center properties

Coordinates 0,0 are at upper left corner of view

Core Graphics Types

CGFloat

C typedef conditionally compiled as float on 32-bit platforms, double on 64-bit

CGPoint

x, y coordinates of origin of a view or graphic element

CGSize

width and height (both CGFloat)

CGRect

origin (CGPoint) and size (CGSize)

// From CGGeometry.h

/* Points. */struct CGPoint { CGFloat x; CGFloat y;};typedef struct CGPoint CGPoint;

/* Sizes. */struct CGSize { CGFloat width; CGFloat height;};typedef struct CGSize CGSize;

/* Rectangles. */struct CGRect { CGPoint origin; CGSize size;};typedef struct CGRect CGRect;

CG Convenience Functions

CGPointMake(CGFloat x, CGFloat y)

Returns CGPoint initialized with provided values

CGPoint myPoint = CGPointMake(0.0, 0.0);

CGSizeMake(CGFloat width, CGFloat height)

Returns CGSize initialized with provided values

CGSize mySize = CGSizeMake(120.0, 240.0);

CGRectMake(CGFloat x, CGFloat y, CGFloat width, CGFloat height)

Returns CGRect initialized with provided values

CGRect myRect = CGRectMake(0.0, 0.0, 120.0, 240.0);

UIWindow

Subclass of UIView

Root of the view hierarchy

Acts as bridge to UIApplication

UIApplication distributes events from the event queue and connects views to the window server

Dispatches events to its subviews

Manages key status

Converts coordinates

windowLevel

keyWindow

makeKeyAndVisible

becomeKeyWindow

makeKeyWindow

resignKeyWindow

convertPoint:toWindow:

convertPoint:fromWindow:

convertRect:toWindow:

convertRect:fromWindow:

sendEvent:

Creating a Window

Use UIScreen to compute initial frame rectangle

+mainScreen class method returns singleton instance

+ (UIScreen *)mainScreen

-bounds method returns main screen's bounds rectangle

-applicationFrame method returns bounds minus the status bar area

Use initWithFrame: method (inherited from UIView) to init window

Designated initializer for UIView and its subclasses

- (id)initWithFrame:(CGRect)frameRect;

CGRect frameRectangle = [[UIScreen mainScreen] applicationFrame];UIWindow *myWindow = [[UIWindow alloc] initWithFrame:frameRectangle];

First App: Hello World!

Create Window-Based App Project

Delete .xib file in the Resources group

Delete the .nib file name in info.plist

Create MyAppDelegate Class

Delete .h and .m files in Classes group

Right-click Classes and select Add > New File...

Select iPhone OS | Cocoa Touch Classes in left pane and choose NSObject subclass

Save as MyAppDelegate

Edit main.m

Replace last argument in UIApplicationMain with @"MyAppDelegate"

Declaring the Delegate

MyAppDelegate.h

Adopt the UIApplicationDelegate protocol

Add window property to contain your application's UIWindow instance

@interface MyAppDelegate : NSObject <UIApplicationDelegate>{ UIWindow *_window;}

// accessor methods

- (UIWindow *)window;- (void)setWindow:(UIWindow *)window;

protocol declaration

- (void)applicationDidFinishLaunching:(UIApplication *)application{ // UIScreen represents the entire screen. Its applicationFrame method // returns the rectangle that corresponds to the entire screen minus // the status bar. CGRect is a C struct containing four floating // point values that represent the x and y coordinates of the upper left // corner, plus width and height. CGRect windowRect = [[UIScreen mainScreen] applicationFrame]; UIWindow *window = [[UIWindow alloc] initWithFrame:windowRect]; [window setBackgroundColor:[UIColor lightGrayColor]]; [self setWindow:window]; // Create an empty view with a different background color so we can // see something on the screen. The four float constants define the // x, y, width, and height of the view's frame rectangle. CGRect viewRect = { 20.0, 100.0, 280.0, 200.0 }; UIView *myView = [[UIView alloc] initWithFrame:viewRect]; [myView setBackgroundColor:[UIColor darkGrayColor]]; // If we don't make the view a subview of our window, it won't be drawn // on the screen. [window addSubview:myView]; // Windows are hidden by default, so make the window visible. 'Key' here // means that the window is capable of receiving key presses from the // keyboard -- though we're not taking advantage of that yet. [window makeKeyAndVisible]; // The calls to +alloc earlier in this method are paired with calls // to release. The -setWindow: message calls -retain, so the window // will not be deallocated until later, when -dealloc is called. Similarly, // -addSubview: indirectly calls -retain, so no worries there either. [window release]; [myView release];}

Implementing the Delegate1. Implement -applicationDidFinishLaunching: delegate method

1.1. Get the application frame rectangle from UIScreen

1.2. Use it to create a UIWindow instance

1.3. Set its background color to [UIColor lightGrayColor]

1.4. Store the instance in the window instance variable

1.5. Create an instance of UIView smaller than the window

1.6. Set its background color to a darker gray ([UIColor darkGrayColor])

1.7. Add the view to the window's subviews

1.8. Tell the window to make itself visible and make itself the key window

1.9. Balance calls to +alloc with calls to -release

2. Implement accessor pair (or synthesize property) for window ivar

3. Implement -dealloc to release window

App Configuration

Some useful keys in Info.plist:

CFBundleDisplayName Name displayed below your app's icon

NSMainNibFile Name of the app's nib file (without the .nib extension)

UIStatusBarStyle Initial status bar style. Default is UIBarStyleDefault

UIStatusBarHidden If set to true, hides the status bar on startup

UIInterfaceOrientation Determines whether app launches in landscape or portrait mode

Keyboard Shortcuts

Action Keys Comment

Build ⌘B Build the app without running; allows you to check for build errors and warnings before trying to run the app

Run ⌘R Build if necessary and run (in Simulator by default; to change target device, use drop-down in upper left corner of Xcode)

Debug ⌥⌘Y Option-Command-Y

Edit ⌘0 Command-zero

Lab Exercise

Get your application running!

If it's working, the application will have a light gray background with a darker gray rectangle on it when the app starts up

Once it's working, we can add some more interesting stuff

Programming Considerations

Frameworks

Foundation

Scaled-down version of desktop Foundation framework

Draws on overall design of AppKit framework

Many classes are similar

Implements similar mechanisms

Target/Action

View Hierarchy

Responder Chain

App StylesProductivity

Hierarchical model to present/manipulate information

Navigation and other controls

Utility

Widget style patterns

Flip for preferences

Immersive

Media players, games, etc. that take over full screen

Use HUD controls for transport control, etc.

Performance Considerations

Constraints of iPhone platform

One app at a time

Save state on applicationWillTerminate:

Memory management

No swap device, minimal RAM

Use AutoreleasePools whenever objects are allocated in tight loops

Use lazy algorithms as much as possible

Free up memory when app receives low memory warning

Application Environment

Apps quit when user switches to another app

Important to start and stop quickly

No background processing after quit

Apps can't access filesystem outside their own sandbox

Try to limit total app size to < 10MB

Users should be able to download in reasonable amount of time

Memory Constraints

256 MB of RAM available to OS + apps on 3G S, 128MB on older devices

Memory must be managed more carefully

Garbage collection not available

Apps get memory warnings when consuming too much RAM

Rule of thumb is 20MB of real memory

App should be prepared to free up RAM by clearing caches, etc.

Cocoa and Cocoa Touch UI based on Model-View-Controller

Model objects encapsulate app data, business logic

UIKit provides View components

Windows, views, and controls

Apps can provide custom components

UIKit also provides controller classes

Apps generally provide custom subclasses

App Architecture

NSRunLoop

Main application event loop

Modal loops

Event and drawing cycle

OS enqueues events generated by user input, network, etc.

Application pulls events off queue and dispatches

At end of event loop, Application propagates message to Views to draw themselves

Graphics and Drawing

Window server connects app to rendering engine

Manages and renders all windows on behalf of apps

Core Graphics and Core Animation

Frameworks for 2D drawing and animation

Integrated with UIKit

OpenGL

Integrated with Core Animation

View Drawing

Quartz

iPhone's 2D drawing engine

Can stroke and fill lines, polygons, text

Supports

Drawing and painting

Transparency, shadows, anti-aliasing

Shading and color management

PDF document creation and metadata access

Framework Drawing Behavior

At the end of each event cycle, framework propagates -display message down the view hierarchy

If a given view needs to redraw, -display makes callback to -drawRect:

You never call display directly; instead you can send setNeedsDisplay on a given UIView or CALayer that needs to be redrawn

However you rarely need to call this method; views usually know when they need to be redrawn

To implement custom drawing, override -drawRect: in a subclass of UIView

Override -drawInContext: for subclasses of CALayer

Views and Layers

UIView has subviews property

NSArray of nested UIView instances

Subviews are drawn on top of parent view (superview) in the order in which they appear in the subviews array

UIView also layer property of type CALayer *

CALayer is like a lightweight UIView

Has sublayers property for nested CALayer instances

Very efficient for animation; 100s of layers can be animated simultaneously

View-Layer Hierarchy

Drawing Text

UIView is responsible for drawing everything rendered to the screen

Subclasses can override drawRect: to customize drawing behavior for classes that do their own drawing

UIKit adds category to NSString (UIStringDrawing)

Methods draw in the current graphics context using current color

Take instance of UIFont as an argument

- drawAtPoint:withFont:

- drawInRect:withFont:

Text Drawing Example

In a subclass of UIView:

- (void)drawRect:(CGRect)rect{ NSString *text = @"Hello, World!"; CGPoint startingPoint = CGPointMake(20.0, 40.0);

[[UIColor whiteColor] set]; UIFont *font = [UIFont systemFontOfSize:36.0]; [text drawAtPoint:startingPoint withFont:font];}

Lab Exercise

Modify your app to draw "Hello World!" on the screen

Create a subclass of UIView called MyHelloView

Implement drawRect: to draw the text

Add an instance of your custom subclass to your app delegate's window (hint: use addSubview:)

Resources

Example Code:

http://www.aboutobjects.com/tutorials.html

Documentation:

Objective-C: http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/ObjectiveC/Introduction/introObjectiveC.html

iPhone: http://developer.apple.com/iphone/library/navigation/index.html

Courses:

http://www.aboutobjects.com/training/courses.html

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