核心位置返回00

Question

下面是完整的方法，我没有把下半年原本因为我知道它的工作原理：

-(void)showDirections 
{ 
    locationManager = [[CLLocationManager alloc] init]; 
    [locationManager setDesiredAccuracy:kCLLocationAccuracyNearestTenMeters]; 
    [locationManager setDelegate:self]; 

    CLLocation *location = [locationManager location]; 

    CLLocationCoordinate2D coordinate = [location coordinate]; 
    NSNumber *myLatitude = [NSNumber numberWithDouble:coordinate.latitude]; 
    NSNumber *myLongitude = [NSNumber numberWithDouble:coordinate.longitude]; 
    double myLatitude2 = [myLatitude doubleValue]; 
    double myLongitude2 = [myLongitude doubleValue]; 


    NSArray *array = [dataHold objectForKey:@"Subtree"]; 
    NSString *latitude = [NSString stringWithFormat:@"%@",[array objectAtIndex:4]]; 
    NSString *longitude = [NSString stringWithFormat:@"%@",[array objectAtIndex:5]]; 
    double clubLatitude = [latitude doubleValue]; 
    double clubLongitude = [longitude doubleValue]; 
    CLLocationCoordinate2D start = { myLatitude2, myLongitude2};  
    CLLocationCoordinate2D destination = { clubLatitude, clubLongitude};   
    NSString *googleMapsURLString = [NSString stringWithFormat:@"http://maps.google.com/?saddr=%1.6f,%1.6f&daddr=%1.6f,%1.6f",start.latitude, start.longitude, destination.latitude, destination.longitude]; 
    [[UIApplication sharedApplication] openURL:[NSURL URLWithString:googleMapsURLString]]; 

} 

Answer 1

两个问题：

1）你正在做一个NSNumber盒/ unbox循环，没有任何用处

2）核心位置是异步的，因此您不能立即返回用户的位置，您必须使用委托方法检索位置是否/何时可用。

下面是一个例子，说明它应该工作：

-(void)showDirections 
{ 
    locationManager = [[CLLocationManager alloc] init]; 
    [locationManager setDesiredAccuracy:kCLLocationAccuracyNearestTenMeters]; 
    [locationManager setDelegate:self]; 

    [locationManager startUpdatingLocation]; 
} 
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation { 
    CLLocationCoordinate2D coord = [newLocation coordinate]; 
    NSArray *array = [dataHold objectForKey:@"Subtree"]; 
    NSString *latitude = [NSString stringWithFormat:@"%@",[array objectAtIndex:4]]; 
    NSString *longitude = [NSString stringWithFormat:@"%@",[array objectAtIndex:5]]; 
    double clubLatitude = [latitude doubleValue]; 
    double clubLongitude = [longitude doubleValue]; 
    NSString *googleMapsURLString = [NSString stringWithFormat:@"http://maps.google.com/?saddr=%1.6f,%1.6f&daddr=%1.6f,%1.6f", coord.latitude, coord.longitude, clubLatitude, clubLongitude]; 
    [[UIApplication sharedApplication] openURL:[NSURL URLWithString:googleMapsURLString]]; 
} 

Answer 2

代码的第四行是问题的开始位置。您无法立即获取该位置，您需要等到位置服务通知代理人有位置可用。我会添加一些评论你的代码解释：

-(void)showDirections 
{ 
    locationManager = [[CLLocationManager alloc] init]; 
    [locationManager setDesiredAccuracy:kCLLocationAccuracyNearestTenMeters]; 
    [locationManager setDelegate:self]; 

    // this is not where you should be looking 
    CLLocation *location = [locationManager location]; 

    // the rest of this function is not included in this example ... 
} 

因为你设置的委托作为“自我”，当前的类，但实施“CLLocationManagerDelegate”协议，它定义了以下两个功能：

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation { /* */ } 
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error { /* */ } 

这就是您将获得提供给您的位置的地方。

不要忘记更新您的类定义如下所示：

@interface MyClass : NSObject <CLLocationManagerDelegate> { 

而作为一个侧面说明，好像你不完全了解代表和他们所服务的宗旨，如果您是新这是罚款到Objective-C，但更熟悉它们一定会让你的生活变得更轻松。

其他一些有用的东西：

• A CoreLocation Tutorial (covers what you are trying to do)