iPhone獲取當前位置（CoreLocation的一些簡單使用）

獲取用戶位置

Core Location框架提供了三種用於追蹤設備當前位置的服務，Core Location框架從內置的蜂窩，Wi-Fi或者GPS來獲取位置

• The significant-change location

  service 提供了低耗電的方法來獲取當前位置，當前位置改變時會發出通知

• The standard location service 提供了一種可設置的方法來獲取當前位置

• Region monitoring 監視特定地區的跨越

如果程序必須使用位置服務 在程序的info.plist中添加UIRequiredDeviceCapabilities鍵，它是一個包含多個字符串的數組，然後添加location-services，gps字符串

１.The Standard Location Service　
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1. Listing 1-1 Starting the standard location service
2. - (void)startStandardUpdates
3. {
4. // 創建location manager
5. if (nil == locationManager)
6. locationManager = [[CLLocationManager alloc] init];
8. locationManager.delegate = self;

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1. <span >　　// 設置獲取位置的精確度，越精確越耗電</span>

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1. <span > locationManager.desiredAccuracy = kCLLocationAccuracyKilometer;
3. // 設置距離過濾器，超過次距離就更新一次位置
4. locationManager.distanceFilter = 500;
6. [locationManager startUpdatingLocation];
7. }</span>

使用location manager之前一般要檢查位置服務是否可用， [plain]

1. <span >+ (BOOL)locationServicesEnabled</span>

當位置信息更新時，會給location manager發送消息

２.Significant-Change Location Service

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1. <span >- (void)startSignificantChangeUpdates
2. {
3. // Create the location manager if this object does not
4. // already have one.
5. if (nil == locationManager)
6. locationManager = [[CLLocationManager alloc] init];
8. locationManager.delegate = self;
9. [locationManager startMonitoringSignificantLocationChanges];
10. }</span>

可以叫醒在後台的程序

３.Region monitoring Service 使用之前調用CLLocationManager的regionMonitoringAvailable and regionMonitoringEnabled
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1. <span >- (BOOL)registerRegionWithCircularOverlay:(MyCircle*)overlay andIdentifier:(NSString*)identifier
2. {
3. // Do not create regions if support is unavailable or disabled.
4. if ( ![CLLocationManager regionMonitoringAvailable] ||
5. ![CLLocationManager regionMonitoringEnabled] )
6. return NO;
8. // If the radius is too large, registration fails automatically,
9. // so clamp the radius to the max value.
10. CLLocationDegrees radius = overlay.radius;
11. if (radius > self.locationManager.maximumRegionMonitoringDistance)
12. radius = self.locationManager.maximumRegionMonitoringDistance;
14. // Create the region and start monitoring it.
15. CLRegion* region = [[CLRegion alloc] initCircularRegionWithCenter:overlay.coordinate
16. radius:radius identifier:identifier];
17. [self.locationManager startMonitoringForRegion:region
18. desiredAccuracy:kCLLocationAccuracyHundredMeters];
20. [region release];
21. return YES;
22. }</span>