1

我的应用程序需要位置服务，我希望只在第一次打开应用程序时启用它们或之前启用它们时运行我的主要方法。

我正在使用以下代码：

- (void)viewDidLoad
{
    [super viewDidLoad];
    if ([CLLocationManager authorizationStatus] == YES) {
        //are enabled, run the JSON request
        [self getDataFromJson];
    } else {
        //is not enabled, so set it up
        NSLog(@"no");
        [locationManager location];
    };

}

-(CLLocationCoordinate2D) getLocation{

    locationManager = [[CLLocationManager alloc] init];
    locationManager.delegate = self;
    locationManager.desiredAccuracy = kCLLocationAccuracyBest;
    locationManager.distanceFilter = kCLDistanceFilterNone;
    [locationManager startUpdatingLocation];
    CLLocation *location = [locationManager location];
    CLLocationCoordinate2D coordinate = [location coordinate];
    return coordinate;

}

-(void)locationManager:(CLLocationManager *)manager didChangeAuthorizationStatus:(CLAuthorizationStatus)status {
    if (status == kCLAuthorizationStatusDenied) {
        //location denied, handle accordingly
        locationFailView.hidden = NO;
        mainView.hidden = YES;
    }
    else if (status == kCLAuthorizationStatusAuthorized) {
        //hooray! begin tracking
        [self getDataFromJson];
    }
}

//class to convert JSON to NSData
- (IBAction)getDataFromJson {
    NSLog(@"running");
    CLLocationCoordinate2D coordinate = [self getLocation];
    NSString *latitude = [NSString stringWithFormat:@"%f", coordinate.latitude];
    NSString *longitude = [NSString stringWithFormat:@"%f", coordinate.longitude];
    ...
}

这段代码现在几乎可以完美运行，除了getDataForJson一次又一次地运行，导致无限循环（即，一次又一次地输出“运行”）。

我怎么会出错所以它只运行一次？

谢谢！

4

1 回答 1

2

在我看来getDataFromJson调用getLocation，它分配一个locationManager实例，其委托调用locationManager:didChangeAuthorizationStatus:，调用getDataFromJson。它仅在启用位置服务时发生，因为getDataFromJson仅在 status == kCLAuthorizationStatusAuthorized时被调用。

getDataFromJson -> getLocation ~> locationManager:didChangeAuthorizationStatus（通过委托）-> getDataFromJson（启用位置服务时）。

于 2013-07-08T19:18:31.707 回答