GPS使用

在 iOS 应用中使用 GPS大致分下面两步：1、添加 CoreLocation.framework；2、生成 CLLocationManager 测量位置。

测试代码如下：

// LocationViewCtrl.h
#import <UIKit/UIKit.h>
#import <CoreLocation/CoreLocation.h>
@interface LocationViewCtrl : UIViewController <CLLocationManagerDelegate>{
CLLocationManager *man;
}
@property(nonatomic, retain) CLLocationManager *man;
@end

LocationViewCtrl.m
#import "LocationViewCtrl.h"
#import <CoreLocation/CoreLocation.h>

@implementation LocationViewCtrl
@synthesize man;

- (void)viewDidLoad {
[super viewDidLoad];
man = [[CLLocationManager alloc] init];

// 如果可以利用本地服务时
if([man locationServicesEnabled]){
// 接收事件的实例
man.delegate = self;
// 发生事件的的最小距离间隔（缺省是不指定）
man.distanceFilter = kCLDistanceFilterNone;
// 精度 (缺省是Best)
man.desiredAccuracy = kCLLocationAccuracyBest;
// 开始测量
[man startUpdatingLocation];
}
}

// 如果GPS测量成果以下的函数被调用
- (void)locationManager:(CLLocationManager *)manager
didUpdateToLocation:(CLLocation *)newLocation
fromLocation:(CLLocation *)oldLocation{

// 取得经纬度
CLLocationCoordinate2D coordinate = newLocation.coordinate;
CLLocationDegrees latitude = coordinate.latitude;
CLLocationDegrees longitude = coordinate.longitude;
// 取得精度
CLLocationAccuracy horizontal = newLocation.horizontalAccuracy;
CLLocationAccuracy vertical = newLocation.verticalAccuracy;
// 取得高度
CLLocationDistance altitude = newLocation.altitude;
// 取得时刻
NSDate *timestamp = [newLocation timestamp];

// 以下面的格式输出 format: <latitude>, <longitude>> +/- <accuracy>m @ <date-time>
NSLog([newLocation description]);

// 与上次测量地点的间隔距离
if(oldLocation != nil){
CLLocationDistance d = [newLocation getDistanceFrom:oldLocation];
NSLog([NSString stringWithFormat:@"%f", d]);
}
}

// 如果GPS测量失败了，下面的函数被调用
- (void)locationManager:(CLLocationManager *)manager
didFailWithError:(NSError *)error{
NSLog([error localizedDescription]);
}
...

    测量精度有以下几类，精度越高越消耗电力。

kCLLocationAccuracyNearestTenMeters	10m
kCLLocationAccuracyHundredMeters	100m
kCLLocationAccuracyKilometer	1km
kCLLocationAccuracyThreeKilometers	3km

    因为在模拟器上不能设置经纬度，所以只能在实际设备中测试你的GPS程序。