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Question

这是完整的方法，我最初没有放置后半部分，因为我知道它有效：

 -(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）您正在执行一个没有任何用处的 NSNumber 装箱/拆箱循环

2）Core Location 是异步的，因此您无法立即返回用户的位置，您必须使用委托方法来检索位置（如果/当位置可用时）。

以下是它应该如何工作的示例：

 -(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开始的地方。您无法立即获取位置，您需要等待位置服务通知代理人位置可用。我将在您的代码中添加一些注释来解释：

-(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 ...
}

由于您将委托设置为“self”，所以当前类但实现“CLLocationManagerDelegate”协议，定义了以下两个函数：

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

您将在那里获得为您提供的位置。

不要忘记像这样更新你的类定义：

@interface MyClass : NSObject <CLLocationManagerDelegate> {

顺便说一句，你似乎没有完全理解委托及其服务的目的，如果你是 Objective-C 的新手，但越来越熟悉它们，这很好。肯定会让您的生活更轻松一些。

其他一些有用的东西：

• CoreLocation 教程（涵盖您想要做的事情）