iPhone development

Different way to show keyboard and resize UIView with text field

2012-01-18T03:43:00.000-08:00

When the soft key board is shown and hidden, it broadcast two notifications. We have listen to the notification to perform anything when the keyboard appears and disappears. s

- (void) viewWillAppear:(BOOL)animated {

[super viewWillAppear:animated];

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:)

name:UIKeyboardWillShowNotification object:nil];

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillHide:)

name:UIKeyboardWillHideNotification object:nil];

}

- (void)viewWillDisappear:(BOOL)animated {

[self.view endEditing:YES];

[super viewWillDisappear:animated];

[[NSNotificationCenter defaultCenter] removeObserver:self

name:UIKeyboardWillShowNotification object:nil];

[[NSNotificationCenter defaultCenter] removeObserver:self

name:UIKeyboardWillHideNotification object:nil];

}

From UIWindow class reference,

Keyboard Notification User Info Keys

Keys used to get values from the user information dictionary of keyboard notifications.

NSString *const UIKeyboardFrameBeginUserInfoKey;
NSString *const UIKeyboardFrameEndUserInfoKey;
NSString *const UIKeyboardAnimationDurationUserInfoKey;
NSString *const UIKeyboardAnimationCurveUserInfoKey;
 
// Deprecated in iOS 3.2 and later.
NSString *const UIKeyboardCenterBeginUserInfoKey;
NSString *const UIKeyboardCenterEndUserInfoKey;
NSString *const UIKeyboardBoundsUserInfoKey;

The notification we receive is,

NSConcreteNotification 0xf5b09c0 {name = UIKeyboardWillHideNotification; userInfo = {

UIKeyboardAnimationCurveUserInfoKey = 0;

UIKeyboardAnimationDurationUserInfoKey = "0.25";

UIKeyboardBoundsUserInfoKey = "NSRect: {{0, 0}, {320, 216}}";

UIKeyboardCenterBeginUserInfoKey = "NSPoint: {160, 372}";

UIKeyboardCenterEndUserInfoKey = "NSPoint: {160, 588}";

UIKeyboardFrameBeginUserInfoKey = "NSRect: {{0, 264}, {320, 216}}";

UIKeyboardFrameChangedByUserInteraction = 0;

UIKeyboardFrameEndUserInfoKey = "NSRect: {{0, 480}, {320, 216}}";

}}

Technique 1- Direct and simple calculation

-(void) keyboardWillShow:(NSNotification *)aNotification

{

NSDictionary* info = [aNotification userInfo];

// Get the frame of the keyboard.

NSValue *centerValue = [info objectForKey:UIKeyboardCenterEndUserInfoKey];

NSValue *boundsValue = [info objectForKey:UIKeyboardBoundsUserInfoKey];

CGPoint keyboardCenter = [centerValue CGPointValue];

CGRect keyboardBounds = [boundsValue CGRectValue];

CGPoint keyboardOrigin = CGPointMake(keyboardCenter.x - keyboardBounds.size.width / 2.0,

keyboardCenter.y - keyboardBounds.size.height / 2.0);

CGRect keyboardScreenFrame = { keyboardOrigin, keyboardBounds.size };

// some calculation...

CGRect viewFrame = self.view.frame;

CGRect keyboardFrame = [self.view.superview convertRect:keyboardScreenFrame fromView:nil];

CGRect hiddenRect = CGRectIntersection(viewFrame, keyboardFrame);

CGRect remainder, slice;

CGRectDivide(viewFrame, &slice, &remainder, CGRectGetHeight(hiddenRect), CGRectMaxYEdge);

self.view.frame = remainder;

}

-(void) keyboardWillHide:(NSNotification *)aNotification

{

CGRect keyboardBounds;

[[aNotification.userInfo valueForKey:UIKeyboardBoundsUserInfoKey] getValue: &keyboardBounds];

float keyboardHeight = keyboardBounds.size.height;

CGRect frame = self.view.frame;

frame.size.height += keyboardHeight;

[UIView beginAnimations:nil context:NULL];

[UIView setAnimationBeginsFromCurrentState:YES];

[UIView setAnimationDuration:0.3f];

self.view.frame = frame;

[UIView commitAnimations];

}

Technique 2

Consider tabBar and keyboard for multiple languages

Define a variable viewIsResized to remember that you have already resized the view. Otherwise if you choose/change language in the keyboard, pressing the globe button, this again call keyboardWillShow and change the view size (I did not tested it though).

When you resize the keyboard, if the view has a tabBar, the keyboard will hide the tabbar. So consider its height too, when resizing the view.

-(void) keyboardWillShow:(NSNotification *)aNotification

{

NSDictionary * userInfo = aNotification.userInfo;

NSTimeInterval animationDuration;

UIViewAnimationCurve animationCurve;

CGRect keyboardFrame;

[[userInfo valueForKey:UIKeyboardAnimationCurveUserInfoKey] getValue:&animationCurve];

[[userInfo valueForKey:UIKeyboardAnimationDurationUserInfoKey] getValue:&animationDuration];

[[userInfo valueForKey:UIKeyboardFrameEndUserInfoKey] getValue:&keyboardFrame];

CFShow(self.view);

if (!viewIsResized) {

CGRect frame = self.view.frame;

[UIView beginAnimations:nil context:nil];

[UIView setAnimationBeginsFromCurrentState:YES];

[UIView setAnimationDuration:animationDuration];

[UIView setAnimationCurve:animationCurve];

frame.size.height -= keyboardFrame.size.height;

if (self.tabBarController) { // consider if there is a tab bar below

frame.size.height += self.tabBarController.tabBar.frame.size.height;

}

self.view.frame = frame;

viewIsResized = YES;

}

[UIView commitAnimations];

}

-(void) keyboardWillHide:(NSNotification *)aNotification

{

CFShow(aNotification);

CFShow(self.view);

NSDictionary * userInfo = aNotification.userInfo;

NSTimeInterval animationDuration;

UIViewAnimationCurve animationCurve;

CGRect keyboardFrame;

[[userInfo valueForKey:UIKeyboardAnimationCurveUserInfoKey] getValue:&animationCurve];

[[userInfo valueForKey:UIKeyboardAnimationDurationUserInfoKey] getValue:&animationDuration];

[[userInfo valueForKey:UIKeyboardFrameEndUserInfoKey] getValue:&keyboardFrame];

if (viewIsResized) {

CGRect frame = self.view.frame;

[UIView beginAnimations:nil context:nil];

[UIView setAnimationBeginsFromCurrentState:YES];

[UIView setAnimationDuration:animationDuration];

[UIView setAnimationCurve:animationCurve];

frame.size.height += keyboardFrame.size.height;

if (self.tabBarController) {

frame.size.height -= self.tabBarController.tabBar.frame.size.height;

}

self.view.frame = frame;

[UIView commitAnimations];

viewIsResized = NO;

}

Objective C - writing a good delegate

2011-12-22T08:02:00.002-08:00

We have write custmozied delegate often in your code. Here is complete design pattern with tips on how to write a good delegate in Objective C.

use @protocol to define the delegate
Its usually considered better to use assign rather than retain when declaring a property that is to be a delegate. If object A is a delegate for object B, then if A is released by its owner, B does not need to reference it anymore. It is also a good practice in dealloc for A, to set any delegate properties that point to A, to null. That way when the object goes to notify A, after it has been released, it doesn’t get an error.
It’s smart to let your protocol inherit from NSObject protocol, this gives you easy access to common methods such as respondsToSelector & performSelector. But it’s an even better idea to declare your delegate ivar not as id but as NSObject* as this also allows gives you access to common NSObject methods not defined in the NSObject Protocol (like performSelectorOnMainthread: and performSelector:AfterDelay:).
Always check if the delegate implemented the required methods.

if ([[self delegate] respondsToSelector:@selector(processSuccesfully:)]) {
[[self delegate] processSuccesfully:YES];
}

In the header file:

@class ClusterAnnotationView;

@protocol ClusterAnnotationViewDelegate <NSObject>

@required

// any required method, you want to use

@optional

- (void) clusterAnnotationView:(ClusterAnnotationView *)annotationView

touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;

- (void) clusterAnnotationView:(ClusterAnnotationView *)annotationView

longPressed:(BOOL)longPressed;

@end

Then your class definition.

@interface ClusterAnnotationView : MKAnnotationView <MKAnnotation> {

id <ClusterAnnotationViewDelegate> delegate;

}

@property (nonatomic, assign) id delegate;

The class implementation with its delegate:

@implementation ClusterAnnotationView

@synthesize coordinate;

@synthesize customCallOutView;

@synthesize delegate;

- (id) initWithAnnotation:(id<MKAnnotation>)annotation

reuseIdentifier:(NSString *)reuseIdentifier

{

self = [super initWithAnnotation:annotation reuseIdentifier:reuseIdentifier];

if (self) {

UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc]

initWithTarget:self action:@selector(longPress:)];

[self addGestureRecognizer:longPress];

[longPress release];

}

return self;

}

// calling delegate's methods.

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

self.customCallOutView.hidden = YES;

if ([self.delegate respondsToSelector:@selector(clusterAnnotationView:touchesBegan:withEvent:)]) {

[self.delegate clusterAnnotationView:self touchesBegan:touches withEvent:event];

}

- (void)longPress:(UILongPressGestureRecognizer*)gesture {

if ([self.delegate respondsToSelector:@selector(clusterAnnotationView:longPressed:)]) {

[self.delegate clusterAnnotationView:self longPressed:YES];

}

@end

Objective C - Property unleashed

2011-12-15T01:57:00.000-08:00

When we define Objective C class, we define property and synthesize them using built-in synthesizing methods.
Properties can nonatomic, assign, copy etc. Here I will go into the meaning of different keywords of defining a property.

Property definitions:
@property (nonatomic, retain) NSString * name;
@property (assign) NSInteger count;

assign:
In your setter method for the property, there is a simple assignment of your instance variable to the new value, eg:

- (void)setString:(NSString*)newString{
    string = newString;
}

This can cause problems since Objective-C objects use reference counting, and therefore by not retaining the object, there is a chance that the string could be deallocated whilst you are still using it.

retain:

this retains the new value in your setter method. For example:

- (void)setString:(NSString*)newString{
    [newString retain];
    [string release];
    string = newString;
}

This is safer, since you explicitly state that you want to maintain a reference of the object, and you must release it before it will be deallocated. This is usual method to have a object property in the class.

copy:

This makes a copy of the string in your setter method:

- (void)setString:(NSString*)newString{
    if(string!=newString)
    {
        [string release];
        string = [newString copy];
    }
}

This is often used with strings, since making a copy of the original object ensures that it is not changed whilst you are using it. In this method your class always own the object no matter what happens to the original object.

UIDatePicker advanced Tutoial

2011-12-08T06:21:00.001-08:00

Here is an example how we can make a date picker to pick a start and end date:

Header file

@class LPStartEndDatePickerController;

//------------------------------------------------------------

@protocol LPStartEndDatePickerControllerDelegate <NSObject>

@optional

- (void) datePickerController:(LPStartEndDatePickerController *) controller

didPickStartDate:(NSDate *)startDate endDate:(NSDate *) endDate;

@end

//------------------------------------------------------------

@interface LPStartEndDatePickerController : UIViewController

<UITableViewDataSource, UITableViewDelegate>

{

id <LPStartEndDatePickerControllerDelegate> delegate;

NSDate * startDate, * endDate;

UIDatePicker * datePicker;

NSDateFormatter * dateFormatter;

NSString * startDateLabel, * endDateLabel;

@private

NSInteger selectedRow;

UITableView * tableView;

}

@property (assign) id <LPStartEndDatePickerControllerDelegate> delegate;

@property (nonatomic, retain) NSDateFormatter * dateFormatter;

@property (nonatomic, retain) NSDate * startDate, * endDate;

@property (nonatomic, retain) NSString * startDateLabel, * endDateLabel;

@property (nonatomic, retain) UIDatePicker * datePicker;

@end

Source code

#import "LPStartEndDatePickerController.h"

//--------------------------------------------------------------------------

@interface LPStartEndDatePickerController ()

@property NSInteger selectedRow;

@property (nonatomic, retain) UITableView * tableView;

@end

//--------------------------------------------------------------------------

@implementation LPStartEndDatePickerController

@synthesize dateFormatter;

@synthesize startDate, endDate;

@synthesize startDateLabel, endDateLabel;

@synthesize datePicker;

@synthesize delegate;

@synthesize selectedRow;

@synthesize tableView;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

{

self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];

if (self) {

// Custom initialization

}

return self;

}

- (void)dealloc

{

[startDate release];

[endDate release];

[dateFormatter release];

[datePicker release];

[startDateLabel release];

[endDateLabel release];

[tableView release];

[super dealloc];

}

- (void)didReceiveMemoryWarning

{

[super didReceiveMemoryWarning];

}

#pragma mark - View lifecycle

- (void) loadView {

CGFloat height = [[UIScreen mainScreen] applicationFrame].size.height

// - [UIApplication sharedApplication].statusBarFrame.size.height

- self.navigationController.navigationBar.frame.size.height;

CGFloat width = [[UIScreen mainScreen] applicationFrame].size.width;

self.view = [[[UIView alloc] initWithFrame:CGRectMake(0, 0, width, height)] autorelease];

self.view.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;

self.view.autoresizesSubviews = YES;

self.view.backgroundColor = [UIColor groupTableViewBackgroundColor];

UIBarButtonItem * doneButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone

target:self

action: @selector(didPressDoneButton)];

self.navigationItem.rightBarButtonItem = doneButton;

[doneButton release];

UIBarButtonItem * cancelButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemCancel

target:self

action: @selector(didPressCancelButton)];

self.navigationItem.leftBarButtonItem = cancelButton;

[cancelButton release];

if (self.title == nil) {

self.title = NSLocalizedString(@"Choose dates", @"");

}

if (self.startDateLabel == nil) {

self.startDateLabel = NSLocalizedString(@"Start date:", @"");

}

if (self.endDateLabel == nil) {

self.endDateLabel = NSLocalizedString(@"End date:", @"");

}

if (self.datePicker == nil) {

self.datePicker = [[UIDatePicker alloc] init];

self.datePicker.datePickerMode = UIDatePickerModeDate;

}

[self.datePicker addTarget:self action:@selector(dateChanged:)

forControlEvents:UIControlEventValueChanged];

if (self.dateFormatter == nil) {

NSString * dateFormatString = [NSDateFormatter dateFormatFromTemplate:@"ddMMyyyy"

options:0

locale:[NSLocale currentLocale]];

self.dateFormatter = [[NSDateFormatter alloc] init];

[self.dateFormatter setDateFormat:dateFormatString];

}

self.tableView = [[UITableView alloc] initWithFrame:CGRectMake(0, 0,

self.view.frame.size.width,

self.view.frame.size.height - self.datePicker.frame.size.height)

style:UITableViewStyleGrouped];

tableView.delegate = self;

tableView.dataSource = self;

[self.view addSubview:tableView];

self.datePicker.frame = CGRectMake(0, tableView.frame.size.height, self.view.frame.size.width, self.datePicker.frame.size.height);

[self.view addSubview:self.datePicker];

//NSLog(@"app = %@ View = %@, tableView = %@, picker = %@ ", NSStringFromCGRect([[UIScreen mainScreen] applicationFrame]), NSStringFromCGRect(self.view.frame), NSStringFromCGRect(tableView.frame), NSStringFromCGRect(datePicker.frame));

}

- (void)viewDidLoad

{

[super viewDidLoad];

}

- (void)viewDidUnload

{

[super viewDidUnload];

}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation

{

// Return YES for supported orientations

return (interfaceOrientation == UIInterfaceOrientationPortrait);

}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView

{

return 1;

}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section

{

return 2;

}

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

{

static NSString *CellIdentifier = @"Cell";

UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:CellIdentifier];

if (cell == nil) {

cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:CellIdentifier] autorelease];

}

// Configure the cell...

if (indexPath.row == 0) {

cell.textLabel.text = startDateLabel;

if (self.startDate == nil) {

cell.detailTextLabel.text = NSLocalizedString(@"select start date", @"");

} else {

cell.detailTextLabel.text = [self.dateFormatter stringFromDate:self.startDate];

}

} else {

cell.textLabel.text = endDateLabel;

if (self.endDate == nil) {

cell.detailTextLabel.text = NSLocalizedString(@"select end date", @"");

} else {

cell.detailTextLabel.text = [self.dateFormatter stringFromDate:self.endDate];

}

return cell;

}

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {

return NSLocalizedString(@"Please choose dates: ", @"");

}

#pragma mark - Table view delegate

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath

{

self.selectedRow = indexPath.row;

//[self showDatePicker];

}

#pragma mark - Action handlers

- (void) didPressDoneButton {

NSString * message;

BOOL validationError = NO;

if (self.startDate == nil) {

message = [NSString stringWithFormat:@"%@ '%@'",

NSLocalizedString(@"Please enter ", @""), self.startDateLabel];

validationError = YES;

} else if (self.endDate == nil) {

message = [NSString stringWithFormat:@"%@ '%@'",

NSLocalizedString(@"Please enter ", @""), self.endDateLabel];

validationError = YES;

}

if (validationError) {

UIAlertView * alertView = [[UIAlertView alloc] initWithTitle:NSLocalizedString(@"Enter date", @"")

message:message delegate:nil

cancelButtonTitle: NSLocalizedString(@"Cancel", @"")

otherButtonTitles:nil];

[alertView show];

[alertView release];

return;

}

if (self.delegate != nil) {

if ([self.delegate respondsToSelector: @selector(datePickerController: didPickStartDate: endDate:)]) {

[self.delegate datePickerController:self didPickStartDate:self.startDate endDate:self.endDate];

} else {

[self.navigationController dismissModalViewControllerAnimated:YES];

}

- (void) didPressCancelButton {

[self.navigationController dismissModalViewControllerAnimated:YES];

}

- (void) dateChanged:(id)sender {

if (selectedRow == 0) {

self.startDate = self.datePicker.date;

} else if (selectedRow == 1) {

self.endDate = self.datePicker.date;

}

[self.tableView reloadData];

}

@end

iPhone Map kit cluster, pin and animation

2011-12-04T23:57:00.001-08:00

In one of my project, I need to have clustering in the map view. I tried to collect information and document here step by step what I have found.

1. Easiest way is to buy a framework found here cost $199. http://getsuperpin.com/.
2. An open source implementation is found here from the same developer above.

To develop it yourself, you need to implement

a clustering algorithm and
animation to expand a clustered pin into multiple

Clustering algorithm

1.
Simple approach can be to divide the MapView into a number of grids. e.g. 5x5 = 25 squares region. Any collection of points inside the grid will make a cluster. Optionally if the number of points in cluster is to a minimum value of 2 or 5, we will avoid clustering and show all the pins.

2.
One approach is that before placing a new pin, check if there's another pin already placed within distance d of the new pin. If there is, don't place the new pin. You need to vary d based on the current zoom level.
You can reduce the number of pins you check against by considering only pins in a bounding box centered on the new pin. The box could be d x d degrees on a side (with d varying based on zoom level).

3.
You can use K-means clustering to group pins into clusters and represent them with a midpoint pin.

4.
Not so elegant solution.

Here's a code snippet that takes an MKAnnotation's coordinates, convert it to a CGPoint relative to the MKMapView, and logs what's the underlying view at that CGPoint.

CGPoint pinPoint = [mapView convertCoordinate:pinView.annotation.coordinate toPointToView:mapView];
NSLog(@"pointing to %@", [[mapView hitTest:pinPoint withEvent:nil] description]);

Put that inside a loop that iterates through all your pins. If the underlying view is another MKAnnotation instance, then hide that pin.

if([[mapView hitTest:pinPoint withEvent:nil] isKindOfClass:[FFMapPinView class]])
    pinView.hidden = YES;

For this to work properly, you need the pinsArray to be ordered so that index 0 is the frontmost pin

Animation to expand a pin

Making the pins expand from the cluster center is actually pretty easy. When you make the new single-pin annotations, set their coordinates to the cluster center:

id <MKAnnotation> pin;
CLLocationCoordinate2D clusterCenter;
// ...
pin.coordinate = clusterCenter;

In viewForAnnotation:, don't animate the new pins:

MKPinAnnotationView *pinView;
// ...
pinView.animatesDrop = NO;

Then, after you've added the pins to the map view, you'll animate moving them to their real positions:

MKMapView *mapView;
id <MKAnnotation> pin;
// ...
// probably loop over annotations
[mapView addAnnotation:pin];
NSTimeInterval interval = 1.0; // or whatever
[UIView animateWithDuration:interval animations:^{
    // probably loop over annotations here again
    CLLocationCoordinate2D realCoord;
    // ...
    pin.coordinate = realCoord;
}];

As for the problem of non-clustered pins, that's harder to answer without knowing the implementation in detail, but I think there are lots of possibilities. You could just have a simple flag that skips the animation. Or you could just treat them exactly the same, and still "cluster" them even when they're solo, and still animate them ... not maximally efficient, but it would work and your code would be cleaner.

Debugging iPhone program in XCode

2011-11-30T04:54:00.001-08:00

A programmer need to debug his program constantly. Debugging in Xcode seems quite complicated. Sometimes in the log output it gives a comprehensible output about a crash or problem, but when you go to the advance level of the program, you may not find all the things you want to debug your program.
Here I will try to document some tips to debug in Xcode. Starting from basic to advanced.

I am using XCode 4.2

Console output
The first thing to do in debug is to use the console output. You can use NSLog() for this purpose.
Remember to enable the console screen on top right corner of Xcode editor.

You get output screen below your editor. Play with options "Local", "All output" etc.

Xcode console

You can run the debugger with the output screen each you run the app, for this you have to a little configuration.

Go to Product -> Edit scheme -> Select Run in the left pane -> Choose Info tab -> Debugger should be GDB or LLDB, do not set None.

Also choose Diagnostics tab and Select "Enable Zombie Objects" to see unwanted memory release crashes.

Breakpoint and Global breakpoint
It is handy to debug by setting a breakpoint to objc_exception_throw(). In the breakpoint navigator pane (Meta-6) you can add a new symbolic breakpoint to objc_exception_throw. You can make it project level or workspace level. The location can be "libobjc.A.dylib".

Another one is the "+[NSException raise:format:arguments:]" breakpoint and its location should be "CoreFoundation"

Using gdb

You can use po - print object to print the symbol in a particular memory location.

po 0x112d0

You can even call methods, like

po [myArray objectAtIndex:0]

Note that it only works on objects, no for non-object stuffs. For non object stuffs use, p :

'p 1'

"info symbol": get the symbolic name for an address

The gdb command I'm going to discuss here is info symbol address which returns the name of any variable or code associated with the memory location given by address.

info symbol 0xa0b05174

list *1106

is useful too as it will list your code around the line number associated with address 11706.

Enable NSZombie
Enabling zombie can trace the allocated object that is deallocated and you are still referencing to that object. This one of the main reason for app crash.
Earlier in xcode you have to enable NSZombie as an environment variable. Now you can do that by Product -> Edit Scheme, select Run options, then in the Diagnostic tab check the "Enable Zombie Objects".

iPhone UIMapView tips and tricks

2011-11-24T00:59:00.001-08:00

Tips and tricks related to UIMapView in iPhone

Maximum values for latitude and longitude delta
When you set a region in the map view you have specify the span in distance or degrees using latitude and longitude delta. The maximum values allows (as CLLocationDegree) is 180.0 only. If you use more than that value, the map view will cause a crash to your application. But I never found that its documented in the API reference documentation.

From apple's documentations, one degree of longitude spans a distance of approximately 111 kilometers (69 miles) .

Radius: Distances from points on the surface to the center range from 6,353 km to 6,384 km (≈3,947–3,968 mi). Several different ways of modeling the Earth as a sphere each yield a convenient mean radius of 6,371 km (≈3,959 mi).

Circumference 40,075.017 km (equatorial) and 40,007.86 km (meridional)

Heading values

Heading values is between 0 to 360 degrees. 0 degrees for North, 90 degrees for East, 180 degrees for South and 270 degrees for West. To get the values in radians divide this value by 180 and then multiply by PI (3.1415926).

Current user location
Map view inherently uses CLLocation to get user location and it have callback. But its the developer's responsibility to show the correct zoom level and user's current location in the map view.

didUpdateUserLocation callback
Map view can have several call to the didUpdateUserLocation so its better to flag when do not need any more user location update. I found it pretty accurate on the first update. But you can check for accuracy values until you get the desired accuracy.

- (void)mapView:(MKMapView *)_mapView didUpdateUserLocation:(MKUserLocation *)_userLocation {

self.userLocation = _userLocation;

NSLog(@"%f",self.currentRegion.span.latitudeDelta);

NSLog(@"updated user location: %f, %f", self.userLocation.location.coordinate.latitude,

self.userLocation.location.coordinate.longitude);

if (!isSpanInitialized) {

//find the nearest branch and ATM, then calculate span to show

MapAnnotation * nearestATM = nil, * nearestBranch = nil;

[self findNearestATM:&nearestATM andBranch:&nearestBranch fromLocation:self.userLocation.location];

CFShow(nearestATM);

CFShow(nearestBranch);

CLLocationDistance atmDist = MKMetersBetweenMapPoints(MKMapPointForCoordinate(nearestATM.coordinate),

MKMapPointForCoordinate(userLocation.location.coordinate));

CLLocationDistance branchDist = MKMetersBetweenMapPoints(MKMapPointForCoordinate(nearestBranch.coordinate),

MKMapPointForCoordinate(userLocation.location.coordinate));

CLLocationDistance maxDist;

if (atmDist > branchDist) maxDist = atmDist;

else maxDist = branchDist;

MKCoordinateRegion targetRegion = MKCoordinateRegionMakeWithDistance(userLocation.location.coordinate, maxDist * 2, maxDist * 2);

currentRegion = targetRegion;

isSpanInitialized = YES;

[_mapView setRegion:currentRegion animated:YES];

}

self.userLocation.title = @"Your location";

self.userLocation.subtitle = [NSString stringWithFormat:@"(long, lat)=(%.4f %.4f)",

self.userLocation.coordinate.longitude,

self.userLocation.coordinate.latitude];

}

Geocoder and reverse geocoder

The built in mapkit geocode sometimes fail to decode the user's current location. It seems it have limitation on the number of calls. In that case, we can use maps.google.com services directly to get the address.

- (void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFailWithError:(NSError *)error {

NSLog(@"Geocoder error: %@", [error description]);

geocoder.delegate = nil;

[geocoder release];

NSString *fetchURL = [NSString stringWithFormat:@"http://maps.google.com/maps/geo?q=%@,%@&output=json&sensor=true",

[NSString stringWithFormat:@"%f",self.userLocation.location.coordinate.latitude],

[NSString stringWithFormat:@"%f",mapView.userLocation.location.coordinate.longitude]];

NSURL *url = [NSURL URLWithString:fetchURL];

NSString *htmlData = [NSString stringWithContentsOfURL:url];

SBJsonParser *parser = [[SBJsonParser alloc] init];

NSDictionary *json = [parser objectWithString:htmlData error:nil];

NSArray *placemark = [json objectForKey:@"Placemark"];

CFShow(json);

}

UILabel - resizing facts

2011-11-23T05:09:00.001-08:00

Tags: iPhone, UILabel, resize, autoresize, font, layout

Apple UILabel component have some missing property.
Two of the mostly needed for me is

Top Left alignment of the text and
Text autoresize with UILabel size.

Font resize with the size of the Label

// resize the font in the label.

UIFont * font = theLabel.font;

int fontSize, lowestSize = 8;

for (fontSize = font.pointSize; fontSize > lowestSize; fontSize --) {

font = [font fontWithSize:fontSize];

CGSize constraintSize = CGSizeMake(theLabel.frame.size.width, MAXFLOAT);

CGSize labelSize = [theLabel.text sizeWithFont:font constrainedToSize:constraintSize lineBreakMode:UILineBreakModeWordWrap];

if (labelSize.height <= theLabel.frame.size.height) {

break;

}

theLabel.font = font;

iPhone NSString operations in Objective C

2011-11-05T02:23:00.000-07:00

Empty String

In the objective C there not an intuitive way to check if the string is empty.

+ (BOOL ) stringIsEmpty:(NSString *) aString {

if ((NSNull *) aString == [NSNull null]) {

return YES;

}

if (aString == nil) {

return YES;

} else if ([aString length] == 0) {

return YES;

} else {

aString = [aString stringByTrimmingCharactersInSet: [NSCharacterSet whitespaceAndNewlineCharacterSet]];

if ([aString length] == 0) {

return YES;

}

return NO;

}

+ (BOOL ) stringIsEmpty:(NSString *) aString shouldCleanWhiteSpace:(BOOL)cleanWhileSpace {

if ((NSNull *) aString == [NSNull null]) {

return YES;

}

if (aString == nil) {

return YES;

} else if ([aString length] == 0) {

return YES;

}

if (cleanWhileSpace) {

aString = [aString stringByTrimmingCharactersInSet: [NSCharacterSet whitespaceAndNewlineCharacterSet]];

if ([aString length] == 0) {

return YES;

}

return NO;

}

String splitter

In one of my latest project, I need to split a string by comma (,) but not all the commas. e.g. If the commas are inside a brackets like () or [], I should not split them.
I can use the API - (NSArray *)componentsSeparatedByString:(NSString *)separator , but i does not server my pupose. So I had to write a custom splitter for my use.

Test cases: []; (); [,,,,]; (,,,,); [inword1, inword2] ourword1, outword2; [word]

customized parser, skip 'splitter' inside () or []

Not checked for double [[]] things.

*/
+ (NSArray *) splitString:(NSString *)originalString byChar:(char)splitter {

if (originalString == nil) return nil;

NSMutableArray * parsedStrings = [[NSMutableArray alloc] initWithCapacity:1];
int length = [originalString length];
int i = 0, lastParsedIndex = 0;
while ( i < length) {

if ([originalString characterAtIndex:i] == '[' || [originalString characterAtIndex:i] == '(' )
{
// loop until the next ] or ) is not found.
do {
i++;
if (i >= (length - 1)) break;
if ([originalString characterAtIndex:i] == ']' || [originalString characterAtIndex:i] == ')' ) {
break;
}
} while (YES);
//i--; // i is already incremented once last time, which should be tested for splitter
} else if ([originalString characterAtIndex:i] == splitter) {
[parsedStrings addObject:[originalString substringWithRange:NSMakeRange(lastParsedIndex, i - lastParsedIndex)]];
lastParsedIndex = i + 1;
}
i++;
}

if (lastParsedIndex != (i-1)) { // i == string length now
[parsedStrings addObject:[originalString substringWithRange:NSMakeRange(lastParsedIndex, i - lastParsedIndex)]];
}

NSArray *temp = [NSArray arrayWithArray:parsedStrings];
[parsedStrings release];
return temp;
}

Testing

+(void) testSplitString {

CFShow([Resources splitString:@"[word1, word2,], word3, word4," byChar:',']); // ideal one

CFShow([Resources splitString:@"some text (word1, word2), [word3, word4] suffix, word 5" byChar:',']); // ideal one

CFShow([Resources splitString:@"[]" byChar:',']);

CFShow([Resources splitString:@"()()" byChar:',']);

CFShow([Resources splitString:@"" byChar:',']);//empty string

CFShow([Resources splitString:@"," byChar:',']);

CFShow([Resources splitString:@",,,," byChar:',']);

CFShow([Resources splitString:@",[,,,],,," byChar:',']);

CFShow([Resources splitString:@",(,,,,,," byChar:',']); // if not finished

}

Gives output - seems okay!

(

"[word1, word2,]",

" word3",

" word4",

)

(

"some text (word1, word2)",

" [word3, word4] suffix",

" word 5"

)

(

"[]"

)

(

"()()"

)

(

)

(

"",

)

(

"",

)

(

"",

"[,,,]",

"",

)

(

"",

"(,,,,,,"

)

String comparison for non english characters
iPhone NSString comparison having Extended ASCII or Latin 1 Unicode character set. I had some problem while sorting esp. Scandinavian character (ÅåÆæØøab) in strings. This makes me write a new comparison routine for this type of strings.

+ (NSComparisonResult) stringCompare:(NSString *)string1 anotherString:(NSString *)string2{

int len1 = [string1 length];

int len2 = [string2 length];

if (len1 < len2) {

int i = 0;

while ( i < len1 && [string1 characterAtIndex:i] == [string2 characterAtIndex:i] )

{

i++;

}

if (i == len1) {

return NSOrderedAscending;

} else if ([string1 characterAtIndex:i] < [string2 characterAtIndex:i]) {

return NSOrderedAscending;

} else {

return NSOrderedDescending;

}

} else { // str1 >= str2 len

int i = 0;

while ( i<len2 && [string1 characterAtIndex:i] == [string2 characterAtIndex:i])

{

i++;

}

if (i == len2 && i == len1) {

return NSOrderedSame;

} else if (i == len2){

return NSOrderedDescending;

} else if ([string1 characterAtIndex:i] < [string2 characterAtIndex:i]) {

return NSOrderedAscending;

} else {

return NSOrderedDescending;

}

return NSOrderedSame;

}