gistfile1.m

- (IBAction)openGPS:(id)sender {
    if (locationManager == nil) {
        locationManager = [[CLLocationManager alloc] init];
        locationManager.delegate = self;
        locationManager.desiredAccuracy = kCLLocationAccuracyBest;  // 越精确，越耗电！
    }
    
    [locationManager startUpdatingLocation];  // 开始定位
}