cocoa touch layer下面的几个点连载之－－CoreLocation

Core Location框架提供了三种用于追踪设备当前位置的服务，Core Location框架从内置的蜂窝，Wi-Fi或者GPS来获取位置The significant-change locationservice 提供了低耗电的方法来获取当前位置，当前位置改变时会发出通知The standard location service 提供了一种可设置的方法来获取当前位置Region monitoring 监视特定地区的跨越 如果程序必须使用位置服务在程序的info.plist中添加UIRequiredDeviceCapabilities键，它是一个包含多个字符串的数组，然后添加location-services，gps字符串１.The Standard Location Service　<span style="font-size:16px;">Listing 1-1  Starting the standard location service- (void)startStandardUpdates{    // 创建location manager    if (nil == locationManager)        locationManager = [[CLLocationManager alloc] init];     locationManager.delegate = self;</span>复制代码<span style="font-size:16px;">　　// 设置获取位置的精确度，越精确越耗电</span>复制代码<span style="font-size:16px;">    locationManager.desiredAccuracy = kCLLocationAccuracyKilometer;     // 设置距离过滤器，超过次距离就更新一次位置    locationManager.distanceFilter = 500;     [locationManager startUpdatingLocation];}</span>复制代码使用location manager之前一般要检查位置服务是否可用，<span style="font-size:16px;">+ (BOOL)locationServicesEnabled</span>复制代码当位置信息更新时，会给location manager发送消息２.Significant-Change Location Service<span style="font-size:16px;">- (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];}</span>复制代码可以叫醒在后台的程序３.Region monitoring Service使用之前调用CLLocationManager的regionMonitoringAvailable and regionMonitoringEnabled <span style="font-size:16px;">- (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.locationManager.maximumRegionMonitoringDistance)      radius = self.locationManager.maximumRegionMonitoringDistance;    // Create the region and start monitoring it.   CLRegion* region = [[CLRegion alloc] initCircularRegionWithCenter:overlay.coordinate                        radius:radius identifier:identifier];   [self.locationManager startMonitoringForRegion:region                    desiredAccuracy:kCLLocationAccuracyHundredMeters];    [region release];   return YES;}</span>复制代码接受位置更新消息当位置更新时，location manager向其代理发送　locationManager:didUpdateToLocation:fromLocation:如果无法获取新位置，则发送locationManager:didFailWithError:<span style="font-size:16px;">// Delegate method from the CLLocationManagerDelegate protocol.- (void)locationManager:(CLLocationManager *)manager    didUpdateToLocation:(CLLocation *)newLocation    fromLocation:(CLLocation *)oldLocation{    // If it's a relatively recent event, turn off updates to save power    NSDate* eventDate = newLocation.timestamp;    NSTimeInterval howRecent = [eventDate timeIntervalSinceNow];    if (abs(howRecent) < 15.0)    {        NSLog(@"latitude %+.6f, longitude %+.6f\n",                newLocation.coordinate.latitude,                newLocation.coordinate.longitude);    }    // else skip the event and process the next one.}</span>复制代码位置更新错误　locationManager:didFailWithError:<span style="font-size:16px;">    if ([error code] != kCLErrorLocationUnknown) {        [self stopUpdatingLocation:NSLocalizedString(@"Error", @"Error")];</span>复制代码If the location service is unable to retrieve a location fix right away, it reports a kCLErrorLocationUnknownerror and keeps trying. In such a situation, you can simply ignore the error and wait for a new event.If the user denies your application’s use of the location service, this method reports a kCLErrorDenied error. Upon receiving such an error, you should stop the location service.If a heading could not be determined because of strong interference from nearby magnetic fields, this method returns　kCLErrorHeadingFailure.<span style="font-size:16px;">typedef enum {   kCLErrorLocationUnknown  = 0,   kCLErrorDenied,   kCLErrorNetwork,   kCLErrorHeadingFailure,   kCLErrorRegionMonitoringDenied,   kCLErrorRegionMonitoringFailure,   kCLErrorRegionMonitoringSetupDelayed,} CLError;</span>复制代码获取移动方向信息<pre name="code" class="plain"><span style="font-size:16px;">- (void)startHeadingEvents {    if (!self.locationManager) {       CLLocationManager* theManager = [[[CLLocationManager alloc] init] autorelease];         // Retain the object in a property.       self.locationManager = theManager;       self.locationManager.delegate = self;    }      // Start location services to get the true heading.    locationManager.distanceFilter = 1000;    locationManager.desiredAccuracy = kCLLocationAccuracyKilometer;    [locManager startUpdatingLocation];      // 开始更新移动方向    if ([CLLocationManager headingAvailable]) {       locManager.headingFilter = 5;       [locManager startUpdatingHeading];    } }  </span>复制代码<span style="font-size:16px;">- (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]; }  </span>复制代码Geocoding Location DataGeocoder对象使用网络服务来将经纬度转换为具体地址信息，iOS当前只支持经纬度转地址信息，不能将位置信息转换为经纬度创建一个MKReverseGeocoder实例，设置代理，调用start方法。代理会接受到 reverseGeocoder:didFindPlacemark:和reverseGeocoder:didFailWithError:<span style="font-size:16px;">@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</span>