CLLocationManager奇怪的行为

Question

I am using location manager to get user location when he/she presses a button.

I just need that exat time location, so I turn off the updates after I get the location.

The thing if that the location I am getting id 0 lat 0 lng at the first time.

-(void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
    lat = newLocation.coordinate.latitude;
    lng = newLocation.coordinate.longitude;
    [locationManager stopUpdatingLocation];
    NSLog(@"New Latlng: %f x %f", lat, lng);
}

When the user presses the button I call: [locationManager startUpdatingLocation];

And right after that I send the location to my server [self sendData]. But the location is zero. At my -sendData method I added an NSLog to track down what was going on and I realized that I was sending the data to the server before the -locationManager:didUpdateToLocation gets called...

2012-04-02 16:06:24.225 MyApp[2892:707] ---- Data sent to server ----
2012-04-02 16:06:25.167 MyApp[2892:707] Nova Latlng: -23.003582 x -43.316311

I tried this but it didnt work as expected either:

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
    [locationManager startUpdatingLocation];
    dispatch_async(dispatch_get_main_queue(), ^{
        [self sendData];
    });
});

How to make the [self sendData] wait until I have the lat and lng variables properly filled?

Answer 1

为什么您在stopUpdatingLocation之后不stopUpdatingLocation拨打该电话？

Answer 2

Put this code

dispatch_async(dispatch_get_main_queue(), ^{
    [self sendData];
});

in didUpdateToLocation: after

[locationManager stopUpdatingLocation];

That should do it. The Location Manager updates come asynchronously, so you have to wait until there is something to process before you try to do anything with the data.