in CLLocationManagerDelegate, when will the method be invoke: locationManager:didUpdateToLocation:fromLocation:
could you explain more detail, if possible could you explain with example? thanks very much
if my current location is changing(eg, I am on a train), does this method be invoked? if yes, how many times or how frequently it is be invoked?
if I stay at one place and not move, does this method be invoked? if yes, how many times or how frequently it is be invoked?
This method is called whenever your iOS device has moved past the distance filter you have set. For example if you set it to
[self.locationManager setDistanceFilter:kCLDistanceFilterNone];
The method will be called every time the device is moved.
A code example of this would be finding the coordinates then assigning those values to labels
- (void)viewDidLoad{
[super viewDidLoad];
altitudeLabel.text = #"0 ft";
ftOrM = YES;
// Note: we are using Core Location directly to get the user location updates.
// We could normally use MKMapView's user location update delegation but this does not work in
// the background. Plus we want "kCLLocationAccuracyBestForNavigation" which gives us a better accuracy.
//
self.locationManager = [[[CLLocationManager alloc] init] autorelease];
self.locationManager.delegate = self; // Tells the location manager to send updates to this object
[self.locationManager setDesiredAccuracy:kCLLocationAccuracyBestForNavigation];
[self.locationManager setDistanceFilter:kCLDistanceFilterNone];
[self.locationManager startUpdatingLocation];
}
-(void)locationManager:(CLLocationManager *)manager didUpdateToLocation: (CLLocation*)newLocation fromLocation:(CLLocation *)oldLocation {
tLatitude = [NSString stringWithFormat:#"%3.5f", newLocation.coordinate.latitude];
tLongitude = [NSString stringWithFormat:#"%3.5f", newLocation.coordinate.longitude];
/* the following returns 0 */
float distanceMeters;
float distanceFeet;
if (ftOrM == YES) {
distanceMeters = newLocation.altitude;
distanceFeet = distanceMeters * 3.2808399;
tAltitude = [NSString stringWithFormat:#"%.02f ft", distanceFeet];
altitudeLabel.text = tAltitude;
}
else {
tAltitude = [NSString stringWithFormat:#"%.02f m", newLocation.altitude];
NSLog(#"Altitude:");
NSLog(#"%#", tAltitude);
altitudeLabel.text = tAltitude;
NSLog(#"Altitude:");
NSLog(#"%#", tAltitude);
}
//[manager stopUpdatingLocation];
}
For the first one this method will invoked, and the frequency depends on the speed.
And if don't change your location then this method will not invoked.
And how much time your location is changing this method will call.
Related
I am building a rails-backed iphone app that uses AFNetworking to create posts at specific locations. So the post model has lat/lng parameters that should be filled in with the client's current location.
At this point, the posts can be made, but the lat/lng comes up as null.
In my (save:) method I pass a conditional to see if a location was found- this is what is failing i.e. "No Location" is logged.
- (void)save:(id)sender {
[self getLocation];
NSArray *locations;
CLLocation *location = [locations objectAtIndex:0];
Post *post = [[Post alloc] init];
post.content = self.contentTextView.text;
post.photoData = UIImagePNGRepresentation(self.imageView.image);
[self.view endEditing:YES];
ProgressView *progressView = [ProgressView presentInWindow:self.view.window];
if (location) {
[post savePostAtLocation:location withBlock:^(CGFloat progress) {
[progressView setProgress:progress];
} completion:^(BOOL success, NSError *error) {
[progressView dismiss];
if (success) {
[self.navigationController popViewControllerAnimated:YES];
} else {
NSLog(#"ERROR: %#", error);
}
}];
} else {
NSLog(#"No Location");
}
}
I have also attempted to implement a locationManager like so
-(void)locationManager:(CLLocationManager *)manager
didUpdateLocations:(NSArray *)locations {
[self getLocation];
}
-(CLLocation *) getLocation{
CLLocationManager * locationManager = [[CLLocationManager alloc] init];
locationManager.delegate = self;
self.locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters;
self.locationManager.distanceFilter = 80.0f;
[locationManager startUpdatingLocation];
CLLocation * location = [locationManager location];
return location;
}
I think ideally I would implement the savePostAtlocation in the CLLocationManagerDelegate where I could pass in the locations array like this:
- (void)locationManager:(CLLocationManager *)manager
didUpdateLocations:(NSArray *)locations
{
CLLocation *location = [locations objectAtIndex:0 /* firstObject */];
if (location) {
[Post createPostAtLocation:location...
But I want to have the post created onSave so I am trying to identify the location but running into some problems..
How do I properly get the current location and pass it into the dictionary?
Any advice on this would be greatly appreciated. Thanks!
Looking at your code, I think you have a slight misunderstanding about how CLLocationManager is designed to work. It looks like you are trying to call [self getLocation] from inside locationManager:didUpdateLocations. This is not correct. Try something like this, inside your save method that is called when you press your button (I would remove the code that's currently in there while testing):
CLLocationManager * locationManager = [[CLLocationManager alloc] init];
locationManager.delegate = self;
self.locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters;
self.locationManager.distanceFilter = 80.0f;
[locationManager startUpdatingLocation];
Then it will start generating location data. When that happens, the phone will automatically call locationManager:didUpdateLocations very rapidly. Then, in locationManager:didUpdateLocations you could use:
CLLocation * location = [manager location];
NSLog(#"%#", location);
To see your location data in the console.
What I have written here should get the phone generating location data for you. What you say about createPostAtLocation: in locationManager:didUpdateLocations is probably the correct way to go. When you get the location data, call [manager stopUpdatingLocation] to make the phone stop, then post the location data you got back to your server.
My application gets the user's location in the appDelegate and calls that location in the viewDidAppear method of some viewControllers. My problem is that the first time the viewController's load, there hasn't been enough time to get the user's location.
Here is my AppDelegate:
- (NSString *)getUserCoordinates
{
NSString *userCoordinates = [NSString stringWithFormat:#"latitude: %f longitude: %f",
locationManager.location.coordinate.latitude, locationManager.location.coordinate.longitude];
locationManager = [[CLLocationManager alloc] init];
locationManager.distanceFilter = kCLDistanceFilterNone; // whenever we move
locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters; // 100 m
[locationManager startUpdatingLocation];
return userCoordinates;
}
- (NSString *)getUserLatitude
{
NSString *userLatitude = [NSString stringWithFormat:#"%f",
locationManager.location.coordinate.latitude];
return userLatitude;
}
- (NSString *)getUserLongitude
{
NSString *userLongitude = [NSString stringWithFormat:#"%f",
locationManager.location.coordinate.longitude];
return userLongitude;
}
Here is what I am using to call the location from the viewControllers:
- (void) viewDidAppear:(BOOL)animated
{
NSString *userLatitude =[(PDCAppDelegate *)[UIApplication sharedApplication].delegate
getUserLatitude];
NSString *userLongitude =[(PDCAppDelegate *)[UIApplication sharedApplication].delegate
getUserLongitude];
}
Anyone have any ideas on how to fix? Thanks so much!
Try to use global variables here. It will be updated as your location updates and you will have updated location cordinates all time.
-(void)didUpdateLocation // location update method of CLLocation Manager class
{
// assign current ordinates values to global variables.
}
Not sure why you posted the same question two times... but see my answer at your other post,
Pass Coordinates from locationManager in appDelegate to viewController
In short, you need to implement the delegate methods of CoreLocation, as those methods are called when a new location is found. In those delegate methods, fire off an NSNotification (which ViewControllers) subscribe to in order to get the new user's location.
I am trying to calculate distance from start using Core Location framework, but when i put the Application on an iPhone device, the data is not correct. Distance keeps on fluctuating and showing random data. Kindly help me out. Also, Altitude is showing zero.
- (void)locationManager:(CLLocationManager *)manager
didUpdateToLocation:(CLLocation *)newLocation
fromLocation:(CLLocation *)oldLocation
{
//Altitude
if(startingPoint==nil)
self.startingPoint=newLocation;
NSString *currentAltitude = [[NSString alloc] initWithFormat:#"%g",
newLocation.altitude];
heightMesurement.text=currentAltitude;
[currentAltitude release];
//Distance
if(startingPoint==nil)
self.startingPoint=newLocation;
//if(newLocation.horizontalAccuracy <= 100.0f) {
// [locationManager stopUpdatingLocation];
//}
//test start.......................................................
//startlocation
NSString *sp = [[NSString alloc]
initWithFormat:#"%f",startingPoint];
NSLog(#"\nStarting point=%#",startingPoint);
ssp.text=sp;
//endlocation
NSString *ep = [[NSString alloc]
initWithFormat:#"%f",newLocation];
NSLog(#"\nStarting point=%#",newLocation);
eep.text=ep;
//test end............................................................
CLLocationDistance mydistance=[newLocation distanceFromLocation:startingPoint];
NSString *tripString = [[NSString alloc]
initWithFormat:#"%f",mydistance];
distLabel.text=tripString;
[tripString release];
//test........................
[sp release];
[ep release];
}//Location Manager ends..
//Time interval of 3 sec....
-(void)locationUpdate:(NSTimer*)timer{
if(timer != nil) [timer invalidate];
[self.locationManager startUpdatingLocation];
}
As to why your altitude may be zero, please see this answer to a similar question.
This may just be a problem with your NSLog statements, but both the starting and ending points are printed out with NSLog statements that say
NSLog(#"\nStarting point=%#",
The way you seem to have scheduled a 3-second timer is not really the way iOS wants you to use CLLocationManager. The preferred way is to tell CLLocationManager what your location criterion are, and then just start it updating. You don't actually need to keep telling it to start updating every 3 seconds. You can just do it once, and then if you ever decide you don't need any more updates, then call
[locationManager stopUpdatingLocation];
If the OS has no new location information, it probably doesn't make sense to keep asking. It'll tell you when it has new location information, via locationManager:didUpdateToLocation:fromLocation. So, I would recommend starting the process more like this:
CLLocationManager* locationManager = [[CLLocationManager alloc] init];
if ([locationManager locationServicesEnabled]) {
Reachability* netStatus = [Reachability sharedReachability];
if (([netStatus internetConnectionStatus] != NotReachable) || ([netStatus localWiFiConnectionStatus] != NotReachable)) {
locationManager.delegate = self;
locationManager.desiredAccuracy = kCLLocationAccuracyBestForNavigation;
locationManager.distanceFilter = 100.0; // 100 m, or whatever you want
[locationManager startUpdatingLocation];
} else {
// TODO: error handling
}
}
self.locMgr = locationManager;
[locationManager release];
The location manager will often deliver you multiple results, with increasing accuracy as it hones in on your location. If you're continually restarting it, I'm wondering if that's causing it problems.
i'm having trouble sending my position when the application lies in the background. I'm using CLLocationManager and startMonitoringSignificantLocationChanges. The posision didUpdateToLocation delegate method is performed once, but not more. I've tried to walk around but no new locations is sent to the server.
I have set the "Required background modes" -> "App registers for location updates" in the info.plist file.
Anyone got an idea on what might be wrong?
Code from where the tracking is started:
CLLocationManager *locationManager = [[CLLocationManager alloc] init];
locationManager.delegate = appDelegate;
[appDelegate setLocationManager:locationManager withDistanceFilter:kCLDistanceFilterNone];
[appDelegate.theLocationManager startMonitoringSignificantLocationChanges];
Code (from CLLocationManagerDelegate):
- (void)setLocationManager:(CLLocationManager*)locationManager withDistanceFilter:(CLLocationDistance)distanceFilter {
// create a new manager and start checking for sig changes
self.theLocationManager.delegate = nil;
[theLocationManager release];
self.theLocationManager = locationManager;
self.theLocationManager.delegate = self;
self.theLocationManager.distanceFilter = distanceFilter;
}
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
NSDate *newLocationTimestamp = newLocation.timestamp;
NSDate *oldLocationTimestamp = oldLocation.timestamp;
int locationUpdateInterval = 15;//15 sec
if (!([newLocationTimestamp timeIntervalSinceDate:oldLocationTimestamp] < locationUpdateInterval)) {
//NSLog(#"New Location: %#", newLocation);
[self updateToLocation:newLocation];
}
}
- (void)updateToLocation:(CLLocation *)newLocation {
NSLog(#"update location!!");
NSString *latitude = [NSString stringWithFormat:#"%f", [newLocation coordinate].latitude];
NSString *longitude = [NSString stringWithFormat:#"%f", [newLocation coordinate].longitude];
[currentUser updatePositionWithLongitude:longitude andLatitude:latitude];
}
Like Bill Brasky said, the accuracy to which you have set your location manager is likely not registering the distance that you have walked. Try setting your location manager accuracy much higher, just to see if works, then dial it back down to a happy medium between accuracy and battery efficiency. Just for testing, take it all the way up:
[appDelegate.theLocationManager setDesiredAccuracy:kCLLocationAccuracyBestForNavigation];
Then instead of:
[appDelegate.theLocationManager startMonitoringSignificantLocationChanges];
try:
[appDelegate.theLocationManager startUpdatingLocation];
The -startMonitoringForSignificantLocationChanges is directly tied to cell tower connectivity. You may need to travel miles to get connection to a new tower and trigger a location change event. I know that the region monitoring is a bit more accurate as it uses updates of location from Wifi, cell tower, and even other apps that inquire on location. You will need to figure out how accurate and how often you need your app to be. You may need to actively monitor location in the background (which would be a battery killer for sure). Hope this helps.
Is there a way to return the users location as a string from a model?
I have a model thats job is to download same JSON data from a web service. When sending in my request I need to add ?lat=LAT_HERE&lng=LNG_HERE to the end of the string.
I have seen tons of examples using the map or constantly updating a label. But I cant find out how to explicitly return the lat and lng values.
Im only 2 days into iPhone dev so go easy on me :)
You need to leverage Core Location, specifically CLLocationManager. Apple doesn't provide any CL programming guide, so just look at one of the samples like LocateMe to see how to do it.
You need to use CLLocationManager like this:
- (void)viewDidLoad
{
// this creates the CCLocationManager that will find your current location
CLLocationManager *locationManager = [[[CLLocationManager alloc] init] autorelease];
locationManager.delegate = self;
locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters;
[locationManager startUpdatingLocation];
}
// this delegate is called when the app successfully finds your current location
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
// retrieve lat and lng in a string from newLocation.coordinate
NSString *lat = [NSString stringWithFormat:#"%d", newLocation.coordinate.latitude];
NSString *lng = [NSString stringWithFormat:#"%d", newLocation.coordinate.longitude];
}
// this delegate method is called if an error occurs in locating your current location
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
NSLog(#"locationManager:%# didFailWithError:%#", manager, error);
}