location ,place

CLLocationManager

CLPlacemark   一个地点包含具体汉字和 经纬度CLLocation

CLLocation  一个点

CLRegion   一个区域

CLLocationCoordinate2D  经纬度

MKCoordinateSpan 经度方向长，维度方向宽

MKMapView

Getting the User’s Location

  #import <CoreLocation/CoreLocation.h>  

There are two different services you can use to get the user’s current location:

• The standard location service is a configurable, general-purpose solution and is supported in all versions of iOS.

• The significant-change location service offers a low-power location service for devices with cellular radios. This service is available only in iOS 4.0 and later and can also wake up an app that is suspended or not running.

Determining Whether Location Services Are Available

• The user can disable location services in the Settings app.

• The user can deny location services for a specific app.

• The device might be in Airplane mode and unable to power up the necessary hardware.

it is recommended that you always call the  locationServicesEnabled  class method of CLLocationManager

 Starting the standard location service

- (void)startStandardUpdates

{

// Create the location manager if this object does not

// already have one.

if (nil == locationManager)

locationManager = [[CLLocationManager alloc] init];

locationManager.delegate = self;

locationManager.desiredAccuracy = kCLLocationAccuracyKilometer;

// Set a movement threshold for new events.

locationManager.distanceFilter = 500;

[locationManager startUpdatingLocation];

}

Starting the significant-change location service

- (void)startSignificantChangeUpdates

{

// Create the location manager if this object does not

// already have one.

if (nil == locationManager)

locationManager = [[CLLocationManager alloc] init];

locationManager.delegate = self;

[locationManager startMonitoringSignificantLocationChanges];

}

Receiving Location Data from a Service

Whether you use the standard location service or the significant-change location service to get location events, the way you receive those events is the same. In iOS 6 and later, the location manager reports events to thelocationManager:didUpdateLocations: method of its delegate when they become available. (In earlier versions of the system, it reports events to the locationManager:didUpdateToLocation:fromLocation:method.) If there is an error retrieving an event, the location manager calls thelocationManager:didFailWithError: method of its delegate instead.

Processing an incoming location event

// Delegate method from the CLLocationManagerDelegate protocol.

- (void)locationManager:(CLLocationManager *)manager

didUpdateLocations:(NSArray *)locations {

// If it's a relatively recent event, turn off updates to save power

CLLocation* location = [locations lastObject];

NSDate* eventDate = location.timestamp;

NSTimeInterval howRecent = [eventDate timeIntervalSinceNow];

if (abs(howRecent) < 15.0) {

// If the event is recent, do something with it.

NSLog(@"latitude %+.6f, longitude %+.6f\n",

location.coordinate.latitude,

location.coordinate.longitude);

}

}

Monitoring Shape-Based Regions

In iOS, regions associated with your app are tracked at all times, including when your app is not running. If a region boundary is crossed while an app is not running, that app is relaunched into the background to handle the event. Similarly, if the app is suspended when the event occurs, it is woken up and given a short amount of time to handle the event.




Determining the Availability of Region Monitoring

Before attempting to monitor any regions, your app should check to see if region monitoring is supported on the current device. There are several reasons why region monitoring might not be available:

• The device may not have the hardware needed to support region monitoring.

• The user may have disabled location services in the Settings app.

• The device might be in Airplane mode and unable to power up the necessary hardware.

For these reasons, it is recommended that you always call the regionMonitoringAvailable andregionMonitoringEnabled class methods of CLLocationManager before attempting to monitor regions.

Defining a Region to Be Monitored

g a region, you must define the region and register it with the system。




Creating and registering a region based on a Map Kit overlay

- (BOOL)registerRegionWithCircularOverlay:(MyCircle*)overlay andIdentifier:(NSString*)identifier

{

// Do not create regions if support is unavailable or disabled.

if ( ![CLLocationManager regionMonitoringAvailable] ||

![CLLocationManager regionMonitoringEnabled] )

return NO;

// If the radius is too large, registration fails automatically,

// so clamp the radius to the max value.

CLLocationDegrees radius = overlay.radius;

if (radius > self.locManager.maximumRegionMonitoringDistance)

radius = self.locManager.maximumRegionMonitoringDistance;

// Create the region and start monitoring it.

CLRegion* region = [[CLRegion alloc] initCircularRegionWithCenter:overlay.coordinate

radius:radius identifier:identifier];

[self.locManager startMonitoringForRegion:region

desiredAccuracy:kCLLocationAccuracyHundredMeters];

[region release];

return YES;

}

If you attempt to register a region and space is unavailable, the location manager calls the locationManager:monitoringDidFailForRegion:withError:  method of its delegate with the kCLErrorRegionMonitoringFailure  error code.




Handling Boundary-Crossing Events for a Region




• locationManager:didEnterRegion:

• locationManager:didExitRegion:

Tips for Conserving Battery Power

Turn off location services when you are not using them。

Use the significant-change location service instead of the standard location service whenever possible.

Use lower-resolution values for the desired accuracy unless doing so would impair your app.

Turn off location events if the accuracy does not improve over a period of time. 




Getting Direction-Related Events

Core Location supports two different ways to get direction-related information:

• Devices with a magnetometer can report the direction in which a device is pointing, also known as its heading.

• Devices with GPS hardware can report the direction in which a device is moving, also known as its course.

Theheading of a device reflects the actual orientation of the device relative to true north or magnetic north.

Thecourse of the device represents the direction of travel and does not take into account the device orientation. 


// Start heading updates.

if ([CLLocationManager headingAvailable]) {

locManager.headingFilter = 5;

[locManager startUpdatingHeading];

}

- (void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading {

if (newHeading.headingAccuracy < 0)

return;

// Use the true heading if it is valid.

CLLocationDirection theHeading = ((newHeading.trueHeading > 0) ?

newHeading.trueHeading : newHeading.magneticHeading);

self.currentHeading = theHeading;

[self updateHeadingDisplays];

}

The actual course and speed information is returned to your app in the same CLLocation objects you use to get the user’s position





Geocoding Location Data

Reverse geocoding  is the process of converting a latitude and longitude into a placemark.  Forward geocoding  is the process of converting place name information into a latitude and longitude value. Reverse geocoding is supported in all versions of iOS but forward geocoding is supported only in iOS 5.0 and later.




geocoders rely on a network service,

Here are some rules of thumb for creating geocoding requests:

• Send at most one geocoding request for any one user action.

• If the user performs multiple actions that involve geocoding the same location, reuse the results from the initial geocoding request instead of starting individual requests for each action.

• When you want to update the location automatically (such as when the user is moving), reissue the geocoding request only when the user's location has moved a significant distance and after a reasonable amount of time has passed. For example, in a typical situation, you should not send more than one geocoding request per minute.

• Do not start a geocoding request at a time when the user will not see the results immediately. For example, do not start a request if your app is in the background or was interrupted and is currently in the inactive state.

Converting Coordinates Into Place Name Informatio

In iOS, you can use either the CLGeocoder or MKReverseGeocoder class to handle reverse-geocoding requests. The CLGeocoder is the preferred class to use and is available in iOS 5.0 and later. However, if your app must run on earlier versions of iOS, you can use the MKReverseGeocoder class.





Geocoding a location using CLGeocoder

@implementation MyGeocoderViewController (CustomGeocodingAdditions)

- (void)geocodeLocation:(CLLocation*)location forAnnotation:(MapLocation*)annotation

{

if (!geocoder)

geocoder = [[CLGeocoder alloc] init];

[theGeocoder reverseGeocodeLocation:location completionHandler:

^(NSArray* placemarks, NSError* error){

if ([placemarks count] > 0)

{

annotation.placemark = [placemarks objectAtIndex:0];

// Add a More Info button to the annotation's view.

MKPinAnnotationView* view = (MKPinAnnotationView*)[map viewForAnnotation:annotation];

if (view && (view.rightCalloutAccessoryView == nil))

{

view.canShowCallout = YES;

view.rightCalloutAccessoryView = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];

}

}

}];

}

@end

 Geocoding a location using MKReverseGeocoder

@implementation MyGeocoderViewController (CustomGeocodingAdditions)

- (void)geocodeLocation:(CLLocation*)location forAnnotation:(MapLocation*)annotation

{

MKReverseGeocoder* theGeocoder = [[MKReverseGeocoder alloc] initWithCoordinate:location.coordinate];

theGeocoder.delegate = self;

[theGeocoder start];

}

// Delegate methods

- (void)reverseGeocoder:(MKReverseGeocoder*)geocoder didFindPlacemark:(MKPlacemark*)place

{

MapLocation* theAnnotation = [map annotationForCoordinate:place.coordinate];

if (!theAnnotation)

return;

// Associate the placemark with the annotation.

theAnnotation.placemark = place;

// Add a More Info button to the annotation's view.

MKPinAnnotationView* view = (MKPinAnnotationView*)[map viewForAnnotation:annotation];

if (view && (view.rightCalloutAccessoryView == nil))

{

view.canShowCallout = YES;

view.rightCalloutAccessoryView = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];

}

}

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

{

NSLog(@"Could not retrieve the specified place information.\n");

}

@end

@implementation MKMapView (GeocoderAdditions)

- (MapLocation*)annotationForCoordinate:(CLLocationCoordinate2D)coord

{

// Iterate through the map view's list of coordinates

// and return the first one whose coordinate matches

// the specified value exactly.

id<MKAnnotation> theObj = nil;

for (id obj in [self annotations])

{

if (([obj isKindOfClass:[MapLocation class]]))

{

MapLocation* anObj = (MapLocation*)obj;

if ((anObj.coordinate.latitude == coord.latitude) &&

(anObj.coordinate.longitude == coord.longitude))

{

theObj = anObj;

break;

}

}

}

return theObj;

}

@end

Converting Place Names Into Coordinates

The more information you can provide to the forward geocoder, the better the results returned to you. The geocoder object parses the information you give it and, if it finds a match, returns some number of placemark objects. The number of returned placemark objects depends greatly on the specificity of the information provided.







[geocoder geocodeAddressString:@"1 Infinite Loop"

completionHandler:^(NSArray* placemarks, NSError* error){

for (CLPlacemark* aPlacemark in placemarks)

{

// Process the placemark.

}

}];