iPhone获取当前位置（CoreLocation的一些简单使用）

获取用户位置

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 location

service 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　

Listing 1-1 Starting the standard location service- (void)startStandardUpdates{ // 创建location manager if (nil == locationManager) locationManager = [[CLLocationManager alloc]
init]; locationManager.delegate = self;　　// 设置获取位置的精确度，越精确越耗电 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];}

使用location manager之前一般要检查位置服务是否可用，+ (BOOL)locationServicesEnabled

当位置信息更新时，会给location manager发送消息

２.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];}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

- (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;}

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:

// 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.}

获取移动方向信息

- (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]; } }

- (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]; }