The minimum image size you should design is 57 × 57 pixels. It is all right to design a larger image because the iPhone automatically resizes it for you. In general, try to design a larger image because doing so prepares your application for the newer devices that Apple may roll out.

You should implement the shouldAutorotateToInterfaceOrientation: method and code the appropriate statements to support the orientation you want. To support all orientations, simply return a YES in this method, like this:

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)
interfaceOrientation {
    // Return YES for supported orientations
    return YES;
}

In the .h file:

//---declare an outlet---
IBOutlet UITextField *nameTextField;
//...
//...
//---expose the outlet as a property---
@property (nonatomic, retain) UITextField *nameTextField;

In the .m file:

@implementation BasicUIViewController
//---generate the getters and setters for the property---
@synthesize nameTextField;

In the .h file:

- (IBAction)btnClicked:(id)sender;

In the .m file:

@implementation BasicUIViewController
//...
//...
- (IBAction)btnClicked:(id)sender {
    //---your code for the action here---
}

To connect a view to its View Controller, do the following within its .xib file:

You use an alert view when displaying a message to the user. If you have several options to let the user choose from, you should use the action sheet.

- (void)loadView {

    //---create a UIView object---
    UIView *view =
        [[UIView alloc] initWithFrame:[UIScreen mainScreen].applicationFrame];
    view.backgroundColor = [UIColor lightGrayColor];

    //---create a Button view---
    frame = CGRectMake(10, 70, 300, 50);

    UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    button.frame = frame;

    [button setTitle:@"Click Me, Please!" forState:UIControlStateNormal];
    button.backgroundColor = [UIColor clearColor];
    button.tag = 2000;
    [button addTarget:self action:@selector(buttonClicked:)
        forControlEvents:UIControlEventTouchUpInside];

    [view addSubview:button];

    self.view = view;

}

First, handle the Did End on Exit event (or implement the textFieldShouldReturn: method in the View Controller). Then call the resignFirstResponder method of the UITextField object to release its first-responder status.

Register for the two notificationsL UIKeyboardWillShowNotification and UIKeyboardWillHideNotification.

//---gets the size of the keyboard---
NSDictionary *userInfo = [notification userInfo];
NSValue *keyboardValue = [userInfo objectForKey:UIKeyboardBoundsUserInfoKey];
[keyboardValue getValue:&keyboardBounds];

-(BOOL)shouldAutorotateToInterfaceOrientation:
(UIInterfaceOrientation)interfaceOrientation {

   return (interfaceOrientation == UIInterfaceOrientationLandscapeLeft ||
           interfaceOrientation == UIInterfaceOrientationLandscapeRight);

}

The frame property defines the rectangle occupied by the view, with respect to its superview (the view that contains it). Using the frame property allows you to set the positioning and size of a view. Besides using the frame property, you can also use the center property, which sets the center of the view, also with respect to its superview. You usually use the center property when you are performing some animation and just want to change the position of a view.

mySecondViewController = [[MySecondViewController alloc]
                                 initWithNibName:nil
                                 bundle:nil];

- (void)viewDidLoad {

    //---create a CGRect for the positioning---
    CGRect frame = CGRectMake(10, 10, 300, 50);

    //---create a Label view---
    label = [[UILabel alloc] initWithFrame:frame];
    label.textAlignment = UITextAlignmentCenter;
    label.font = [UIFont fontWithName:@"Verdana" size:20];
    label.text = @"This is a label";

    //---create a Button view---
    frame = CGRectMake(10, 250, 300, 50);
    button = [[UIButton buttonWithType:UIButtonTypeRoundedRect]
             initWithFrame:frame];

[button setTitle:@"OK" forState:UIControlStateNormal];
    button.backgroundColor = [UIColor clearColor];

    [self.view addSubview:label];
    [self.view addSubview:button];

    [super viewDidLoad];
}

//---add the action handler and set current class as target---
    [button addTarget:self
        action:@selector(buttonClicked:)
        forControlEvents:UIControlEventTouchUpInside];

//...
//...
//...

-(IBAction) buttonClicked: (id) sender{
    //---do something here---
}

Codefile [TabBarAndNav.zip]

You can turn off the highlighting effect by selecting the Info button in Interface Builder and viewing its attributes in the Attributes Inspector window. Deselect the option named "Show Touch On Highlight."

Assuming that you want to pass a string from the FlipsideViewController to the MainViewController, the following statements that appear in bold show how you can pass data from one view to another using a property:

FLIPSIDEVIEWCONTROLLER.H

#import "AddCountryViewController.h";

@protocol FlipsideViewControllerDelegate;

@interface FlipsideViewController : UIViewController
<AddCountryViewControllerDelegate> {
id <FlipsideViewControllerDelegate> delegate;

//---internal member---
    NSString *str;

}

@property (nonatomic, assign) id <FlipsideViewControllerDelegate> delegate;

//---expose the member as a property---
@property (nonatomic, retain) NSString *str;

- (IBAction)done;
- (IBAction)add;
@end

@protocol FlipsideViewControllerDelegate
- (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller;
@end

FLIPSIDEVIEWCONTROLLER.M

#import "FlipsideViewController.h"

@implementation FlipsideViewController

@synthesize delegate;

//---generates the getter and setter for the property---
@synthesize str;

- (IBAction)done {

    //---set a value to the property---
    self.str = @"Some text";

    [self.delegate flipsideViewControllerDidFinish:self];
}

MAINVIEWCONTROLLER.M

- (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller {

    //---prints out the string obtained in the Debugger Console window---
    NSLog(controller.str);

    [self dismissModalViewControllerAnimated:YES];
}

The two protocols are UITableViewDataSource and UITableViewDelegate.

The UITableViewDataSource protocol contains events in which you can populate the Table view with various items.

The UITableViewDelegate protocol contains events in which you can handle the selection of rows in a Table view.

To add an index list to your Table view, you need to implement the sectionIndexTitlesForTableView: method.

The three disclosure and checkmark images are as follows:

The UITableViewCellAccessoryDetailDisclosureButton image handles a user's tap event. The event name is tableView:accessoryButtonTappedForRowWithIndexPath:.

For retrieving preferences settings values, you use the objectForKey: method. For saving preferences settings values, you use the setObject:forKey: method.

You can either remove the application from the device or Simulator, or you can remove the file ending with application_name.plist in the application folder within the Simulator.

The Add Child button is represented by three horizontal lines. It adds a child item to the currently selected item. The Add Sibling button, on the other hand, is represented by a plus sign (+). It adds an item on the same level as the currently selected item.

The sqlite3_exec() function is actually a wrapper for the three functions: sqlite3_prepare(); sqlite3_step(); and sqlite3_finalize(). For nonquery SQL statements (such as for creating tables, inserting rows, and so on), it is always better to use the sqlite3_exec() function.

To obtain a C-style string from an NSString object, use the UTF8String method from the NSString class.

NSString *qsql = @"SELECT * FROM CONTACTS";
sqlite3_stmt *statement;

if (sqlite3_prepare_v2( db, [qsql UTF8String], −1, &statement, nil) ==
    SQLITE_OK) {

        while (sqlite3_step(statement) == SQLITE_ROW)
        {
            char *field1 = (char *) sqlite3_column_text(statement, 0);
            NSString *field1Str = [[NSString alloc] initWithUTF8String: field1];

            char *field2 = (char *) sqlite3_column_text(statement, 1);
            NSString *field2Str = [[NSString    alloc] initWithUTF8String: field2];

            NSString *str = [[NSString alloc] initWithFormat:@"%@ - %@",
                                field1Str, field2Str];
            NSLog(str);

            [field1Str release];

[field2Str release];
            [str release];
        }
        //---deletes the compiled statement from memory---
        sqlite3_finalize(statement);
}

The three folders are Documents, Library, and tmp. The Documents folder can be used by the developer to store application-related data. The Library stores application-specific settings, such as those used by the NSUserDefaults class. The tmp folder can be used to store temporary data that will not be backed up by iTunes.

The NSDictionary class creates a dictionary object whose items are immutable; that is, after it is populated, you can no longer add items to it. The NSMutableDictionary class, on the other hand, creates a mutable dictionary object that allows items to be added to it after it is loaded.

Location of the Documents directory on a real device:

/private/var/mobile/Applications/<application_id>/Documents/

Location of the tmp directory on a real device:

/private/var/mobile/Applications/<application_id>/tmp/

The four events are as follows:

When you multi-tap, you tap a single point in quick succession. This is similar to double-clicking in Mac OS X. When you multi-touch, on the other hand, you touch multiple contact points on the screen.

Pressing the Option key allows you to simulate multi-touch on the iPhone Simulator.

The three affine transformations are translation, rotation, and scaling.

The only way to pause the NSTimer object is to call its invalidate method. To make it continue, you have to create a new NSTimer object.

The beginAnimations and commitAnimations methods of the UIView class allow you to enclose blocks of code that cause visual changes so that the changes in visual appearance will be animated and not appear to change abruptly.

For invoking Safari:

@"http://www.apple.com"

For invoking Mail:

@"mailto:[email protected]&subject=Hello&body=Content of email"

For invoking SMS:

@"sms:96924065"

For invoking Phone:

@"tel:1234567890"

The class name is UIImagePickerController.

The class name is ABPeoplePickerNavigationController.

The protocol is UIAccelerometerDelegate.

The three events are

For the first-generation iPhone, Core Location uses cell tower triangulation and Wi-Fi triangulation to determine its position. This is because first-generation iPhone does not have a built-in GPS receiver. For second- and third-generation devices, Core Location uses the three different methods. For iPod Touch, it uses only Wi-Fi triangulation because it has neither a GPS receiver nor cellular connectivity.