iPhone App Development

What is SQLite?

2012-01-23T22:46:00.000-08:00

SQLite is an embedded SQL database engine. Unlike most other SQL databases, SQLite does not have a separate server process. SQLite reads and writes directly to ordinary disk files. A complete SQL database with multiple tables, indices, triggers, and views, is contained in a single disk file. The database file format is cross-platform - you can freely copy a database between 32-bit and 64-bit systems or between big-endian and little-endian architectures. These features make SQLite a popular choice as an Application File Format. Think of SQLite not as a replacement for Oracle but as a replacement for fopen()

And it is,
a. Single user
b. File based
c. Cross Platform (can be used across multiple platforms)
d. ANSI based C library i.e., pure C API.

SQLite tools:
- SQLite Manager
- sqlite3 command line utility

Creating the DB through command line:

$ sqlite3 Example.database
SQLite version 3.6.12
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite>

.help for more commands

.quit to quit from the sqlite prompt

After successful creation of database, the sqlite prompt gets opened and we can create tables.

For the SQL queries syntax, please refer http://www.sqlite.org/

What is UIView's bounds and frame?

2012-01-22T06:33:00.000-08:00

The UIView class defines a rectangular area on the screen and the interfaces for managing the content in that area. At runtime, a view object handles the rendering of any content in its area and also handles any interactions with that content. The UIView class itself provides basic behavior for filling its rectangular area with a background color. More sophisticated content can be presented by subclassing UIView and implementing the necessary drawing and event-handling code yourself. The UIKit framework also includes a set of standard subclasses that range from simple buttons to complex tables and can be used as-is. For example, a UILabel object draws a text string and a UIImageView object draws an image.

View drawing occurs on an as-needed basis. When a view is first shown, or when all or part of it becomes visible due to layout changes, the system asks the view to draw its contents. For views that contain custom content using UIKit or Core Graphics, the system calls the view’s drawRect: method. Your implementation of this method is responsible for drawing the view’s content into the current graphics context, which is set up by the system automatically prior to calling this method. This creates a static visual representation of your view’s content that can then be displayed on the screen.

Creating view programmatically:

CGRect  viewRect = CGRectMake(10, 10, 100, 100);

UIView* myView = [[UIView alloc] initWithFrame:viewRect];

Important method in drawing the content on to the view:

drawRect: - Implement this method if your view draws custom content. If your view
does not do any custom drawing, avoid overriding this method.

bounds: - The bounds rectangle, which describes the view’s location and size in its 
own coordinate system.

frame: - The frame rectangle, which describes the view’s location and size in its

superview’s coordinate system.

iPhone sensors

2012-01-22T06:24:00.000-08:00

There are various sensors built into most devices iPhone, iPad, and iPod touch that allow them to perform some of their interface featrures. Without these sensors, none of the devices would be what we know them as today. The sensors are:

Proximity sensor – This sensor can determine how close the iPhone is to your face. This sensor is what helps the iPhone turn off its screen automatically whenever you hold the phone up to your ear. This is necessary to prevent accidental button clicks by the side of your head when talking. This sensor is only on the iPhone (since the other devices don't need it).

Motion sensor/accelerometer – This sensor enables the iPod touch, iPad, or iPhone’s screen to automatically switch from landscape to portrait modes and back again based on whether you’re holding the phone up and down or sideways. This sensor is also present in the iPad.

Ambient Light sensor – This sensor can determine how much light is available in the area surrounding the iPhone, iPod touch, and iPad and automatically adjust the brightness of the screen in order to conserve battery life.

Moisture sensor - The devices also contains a fourth sensor, though this one isn’t related to the interface. The water sensor is a little red tab that appears in the dock connector when the phone has been submerged in water. It can also appear as a red dot in the headphone jack.

iPhone 4 Gyroscope

The iPhone 4, 4th gen. iPod touch, and iPad 2 adds another sensor: a three-axis gyroscope. When combining the gyroscope with the accelerometer, this gives these devices six axes on which the it can operate. This is designed to make them more sensitive, responsive, and powerful for gaming.

Fast Enumeration

2012-01-22T04:02:00.000-08:00

This variant of the for loop sets up a fast enumeration. var is a variable whose type can also be declared , expression is an expression that produces a result that conforms to the NSFastEnumeration protocol.Typically, expression is a collection, such as an array or a dictionary.

for ( var in expression )

programStatement

Ex: for (NSString *empName in employees) {

NSLog(@"empName = %@", empName);

}

Note: The fast enumeration is not index based like for loop.

Mac OS X and IOS architecture

2012-01-22T03:30:00.000-08:00

Mac OS X Architecture

IOS Architecture

Type Introspection

2012-01-22T02:34:00.000-08:00

NSObject is a root class, and so doesn’t have a superclass. It defines the basic framework for Objective-C objects and object interactions. It imparts to the classes and instances of classes that inherit from it the ability to behave as objects and cooperate with the runtime system.

A class that doesn’t need to inherit any special behavior from another class should nevertheless be made a subclass of the NSObject class. Instances of the class must at least have the ability to behave like Objective-C objects at run time. Inheriting this ability from the NSObject class is much simpler and much more reliable than reinventing it in a new class definition.

Type Introspection

Instances can reveal their types at runtime. The `isMemberOfClass:` method, defined in the `NSObject` class, checks whether the receiver is an instance of a particular class:

if ( [anObject isMemberOfClass:someClass] )

...

The isKindOfClass: method, also defined in the NSObject class, checks more generally whether the receiver inherits from or is a member of a particular class (whether it has the class in its inheritance path):

if ( [anObject isKindOfClass:someClass] )

...

The set of classes for which isKindOfClass: returns YES is the same set to which the receiver can be statically typed.

Introspection isn’t limited to type information. Later sections of this chapter discuss methods that return the class object, report whether an object can respond to a message, and reveal other information.

NSObject class reference for more on isKindOfClass:, isMemberOfClass:, and related methods.

How to play an audio file on launch of IOS application?

2012-01-18T01:28:00.001-08:00

Apple provided a very good framework called ‘AVFoundation’ provides an Objective-C interface for managing and playing the audio-visual media in your IOS applications.

Please follow the below steps to integrate the audio file to your project:

1. Add the ‘AVFoundation.framework’ to your frameworks folder in the project.

2. Add the statement #import <AVFoundation/AVFoundation.h>

3. Add the file ‘Output.aif’ (an audio file) to your project.

4. Have the following snippet of code in your viewDidLoad method

NSString *path = [[NSBundle mainBundle] pathForResource:@”Output” ofType:@”aif”];

AVAudioPlayer *theAudio =

[[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:path] error:NULL];

theAudio.delegate = self;

[theAudio play];

5. Run the application. You will start listening the music.

How to change of default title font in the UIActionSheet?

2012-01-18T01:27:00.004-08:00

There is no direct way to access the UIActionSheet’s default title properties. There are couple of ways you can do this.

One is, to customize the UIActionSheet.

Second is, to add the label as the sub-view to the UIActionSheet, and set the default title to be nil. But if you do this, there are some other changes apart from adding the label as title. You need to set the frame of the buttons (of type ‘UIThirdPartButton’) inside the UIActionSheet. The code looks like something as follows:

UILabel *titleLabel =

[[UILabel alloc] initWithFrame:CGRectMake(0.0, 0.0, 320.0, 50.0)];

titleLabel.font = [UIFont boldSystemFontOfSize:16.0];

titleLabel.textAlignment = UITextAlignmentCenter;

titleLabel.backgroundColor = [UIColor clearColor];

titleLabel.textColor = [UIColor whiteColor];

titleLabel.text = k3PPTitle;

[actionSheet addSubview:titleLabel];

[titleLabel release];

actionSheet.actionSheetStyle = UIActionSheetStyleDefault;

[actionSheet showInView:self.view];

CGRect actionSheetRect = actionSheet.frame;

actionSheetRect.origin.y -= 40.0;

actionSheetRect.size.height = 300.0;

actionSheet.frame = actionSheetRect;

for (int counter = 0; counter < [[actionSheet subviews] count]; counter++) {

UIView *object = [[actionSheet subviews] objectAtIndex:counter];

if ([object class] == NSClassFromString(@”UIThreePartButton”)) {

CGRect frame = object.frame;

frame.origin.y = frame.origin.y + 30.0;

object.frame = frame;

}

How to implement single/double click on the UITableView?

2012-01-18T01:27:00.002-08:00

To get the touch/tap/move count on any control, there are certain methods in the UIResponder class.

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event

To get the single/double click actions on UITableView, please follow the below steps:

1. Create a CustomTableViewCell, sub-class of the UITableViewCell. And override the above mentioned methods.

#import ”CustomTableViewCell.h”

@implementation CustomTableViewCell

- (void)dealloc {

[super dealloc];

}

- (void)drawRect:(CGRect)rect {

CGContextRef ctx = UIGraphicsGetCurrentContext();

// Use the same color and width as the default cell separator for now

CGContextSetRGBStrokeColor(ctx, 0.5, 0.5, 0.5, 1.0);

CGContextSetLineWidth(ctx, 0.5);

for (int i = 0; i < [columns count]; i++) {

CGFloat f = [((NSNumber*) [columns objectAtIndex:i]) floatValue];

CGContextMoveToPoint(ctx, f, 0);

CGContextAddLineToPoint(ctx, f, self.bounds.size.height);

}

CGContextStrokePath(ctx);

[super drawRect:rect];

}

- (void)addColumn:(CGFloat)position {

[columns addObject:[NSNumber numberWithFloat:position]];

}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

UITouch *aTouch = [touches anyObject];

NSLog(@”touchesBegan tapCount = %d”, [aTouch tapCount]);

}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {

UITouch *aTouch = [touches anyObject];

NSLog(@”touchesCancelled tapCount = %d”, [aTouch tapCount]);

}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {

UITouch *aTouch = [touches anyObject];

NSLog(@”touchesEnded tapCount = %d”, [aTouch tapCount]);

}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {

UITouch *aTouch = [touches anyObject];

NSLog(@”touchesMoved tapCount = %d”, [aTouch tapCount]);

}

2. In the UITableView’s cellForRowAtIndexPath method, add the

CustomTableViewCell instead of UITableViewCell.

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

NSString *MyIdentifier = [NSString stringWithFormat:@"MyIdentifier %i", indexPath.row];

CustomTableViewCell *cell = (CustomTableViewCell *)[tableView dequeueReusableCellWithIdentifier:MyIdentifier];

if (cell == nil) {

cell = [[[CustomTableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:MyIdentifier] autorelease];

}

UILabel *regNoLabel = [[UILabel alloc] initWithFrame:CGRectMake(20, 3, 150, 15)];

//regNoLabel.text = [[self.resultArray objectAtIndex:indexPath.section] valueForKey:@”Ent_Regn_Nbr”];

regNoLabel.text = @”Apple”;

regNoLabel.font = [UIFont systemFontOfSize:12.0];

[cell addSubview:regNoLabel];

[regNoLabel release];

return cell;

}

When you test the application with this, you can observe the tap count in the logs.

Automatic Reference Counting in IOS5

2012-01-18T01:27:00.000-08:00

Automatic Reference Counting (ARC) for Objective-C makes memory management the job of the compiler. By enabling ARC with the new Apple LLVM compiler, you will never need to type retain or release again, dramatically simplifying the development process, while reducing crashes and memory leaks. The compiler has a complete understanding of your objects, and releases each object the instant it is no longer used, so apps run as fast as ever, with predictable, smooth performance.

How to download a large file with the iPhone SDK and avoid memory usage issues?

2012-01-18T01:26:00.002-08:00

I was facing some problem while downloading the large content:
Using the NSURLConnection class to download a large file in an iPhone application, but it crashes every so often because it’s using too much memory. I’m doing the usual NSURLConnection usage, to append the received data to a NSMutableData object.

Solution to the above problem is:
In the delegate method connectionDidReceiveData, we can store the content in the file

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{     
 filename = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,

NSUserDomainMask, YES) objectAtIndex:0] stringByAppendingPathComponent:save_name];     
 NSFileHandle *file1 = [NSFileHandle fileHandleForUpdatingAtPath: filename];     
 [file1 writeData: data];    
 [file1 closeFile]; 
}

6 steps for better designing of any application

2012-01-18T01:26:00.000-08:00

Structure
Navigation
Reduction
Appearance
Feedback
Optimization

Structure to be defined by User Mental Model, the way a task is perceived by the end user.

Memory Management Tips!!!

2012-01-18T01:25:00.001-08:00

Respond to Memory Warnings
Avoid Using Autoreleased Objects
Use Lazy Loading and Reuse
Avoid UIImage’s imageNamed:
Build Custom Table Cells and Reuse Them Properly
Override Setters Properly
Beware of Delegation
Use Instruments
Use a Static Analysis Tool
Use NSZombieEnabled

iPhone App Development

What is SQLite?

What is UIView's bounds and frame?

iPhone sensors

Fast Enumeration

Mac OS X and IOS architecture

Type Introspection

Type Introspection

Instances can reveal their types at runtime. The isMemberOfClass: method, defined in the NSObject class, checks whether the receiver is an instance of a particular class:

if ( [anObject isMemberOfClass:someClass] )

How to play an audio file on launch of IOS application?

How to change of default title font in the UIActionSheet?

How to implement single/double click on the UITableView?

Automatic Reference Counting in IOS5

How to download a large file with the iPhone SDK and avoid memory usage issues?

6 steps for better designing of any application

Memory Management Tips!!!

Instances can reveal their types at runtime. The `isMemberOfClass:` method, defined in the `NSObject` class, checks whether the receiver is an instance of a particular class: