The determination of a position takes some time. When and where should the location manager be started?
Now I'm starting the location update one view before the result view (which needs the location) is loaded. If the user taps to fast I get 0.0 coordinates.
To get the right timing the startUpdatingLocation should be called three views before the result view. The problem here is I would have to pass the value trough this three view controllers.
The next thing is that I need the location also in another view (not the views mentioned above). I thought I will create an own location listener class. But when will this class be instantiated and the coordinates (longitude, latitude) passed through? A protocol doesn't help me, because only the class which created my location listener will get the results back.
I read a bit and come up with the following possible solutions:
1) Use of the Notification Center (see this solution)
2) Create a property of my location manager in the AppDelegate
At 1) I would have the problem that the view, which needs the results wouldn't have be created before.
How would the implementation of 2) would look like? I create an instance of the location manager in the app delegate and then I access some ivars like latitude/longitude of the AppDelegate? If I would take the solution described here I would have to implement the CLLocationManagerDelegate every time. Wouldn't it be better to have one class for doing that?
Perhaps you have a third solution?
A third solution may be to use a singleton class where you store the latitude and longitude of the location in a CLLocationCoordinate2D. You can then use the following code to access the stored coordinate from any view in your project
DataController* dataController = [DataController sharedDataController];
CLLocationCoordinate2D currentLocationCoordinate = dataController.coordinate;
Related
I have two views in my app, one is a general view where CoreLocation works away calculating the users location while the user is doing other stuff in the view. The second view is accessed by the user when they touch a button allowing them to locate themselves more accurately using a mapview and MapKit, i would like the mapview in this view to show the location that CoreLocation has already identified in the first view AND to continue displaying this location based on updates from CoreLocation in the other view.
Is the best way here to create a singleton that encapsulates the CoreLocation stuff and have this referenced in the view with the map, or to use notifications ? or to use some other better practice for my scenario ?
Thanks
I have a couple of apps that use CoreLocation in multiple places. From what I've read, you definitely want there to be just one instance of CLLocationManager. It's worked great as a singleton for me.
Hope this helps!
If I were you, I would do it this way:
Decide which view is going to be always loaded.
I assume, you want CalculatingView is loaded all the time, and MapView will be loaded/unloaded based on the user action.
Allocate and initialize a pointer to CLLocationManager inside CalculatingView. This will provide location property and also call delegate messages. Since the CalculatingView is loaded and retained, this pointer is always working too.
Set CLLocationManager's delegate to be CalculatingView, which might also be called self, if this view has allocated and initialized CLLocationManager pointer.
Implement delegate methods of CLLocationManager, in CalculatingView
If you like to, you can have MapView to be allocated and initialized within CalculatingView. But it's ok to have it in other places, as long as you can send message to MapView. Make sure they are valid by checking if it's not nil or if it respondsToSelector.
When the CLLocationManager's delegate, which is CalculatingView receives messages, send a message to MapView.
It's like relaying messages, but the messages that MapView should respond to don't have to be the same messages sent to CalculatingView like delegate method calls from CLLocationManager
By checking if MapView is valid, meaning if it's loaded to be displayed, you can decide to send messages to MapView or not
The essence is to decide which view is loaded consitently, to use delegate methods for sending(or relaying) messages to other pointers(in this cases, MapView pointer).
The singleton is good, but unless you are going to use CLLocationManager from multiple places, like more than 3~4 places, it's not that necessary, I think
Hope I didn't confuse you. Based on what you posted, it seems like this way can be simple solution for your goal. If I didn't catch your true intention, please let me know.
I am not sure this is the best way, but I've been setting up my main controller (the one that is loaded first) as a location manager delegate. When the location updates it fires off a notification with the new location as the notification object. Any controllers listening can then use that data however they need it.
As an aside, Apple's LocateMe app instantiates the location manager three times. So, by their example, having multiple LocationManagers might not be a problem.
From what I've read, best practice for this is to add CLLocationManager to your App Delegate as you can access it from any view.
Short sample code to put in your view where you need the CLLocationManager
....imports....
#implementation YourViewController
- (void)viewDidLoad {
self.myLocationManager = [[UIApplication sharedApplication] delegate].yourLocationManagerVarName;
}
#end
Hop that helps.
Maybe you should consider a MVC oriented approach. From your description your are missing a model layer representation of your user. Defining a simple User class with a basic CLLocation property would be a first step.
#interface User {}
#property (nonatomic, retain) CLLocation *location;
#end
#implementation User
#synthesize location;
- (void)dealloc {
self.location = nil;
[super dealloc];
}
#end
The same instance of the User will be passed to your view controller. It may be created in the app delegate.
Next create location services object for your app. It will start the CLLocationManager, and give the location to your user. You may have to set the GPS accuracy, ignore frames you don't want, and implement basic LBS logic here.
At this point, you have a feature full app, without any UI. This is a good design in the way it can be reused and tested.
Now stack your UI on top of that. Give your root controller a pointer to the User instance in your app delegate. Your view controller pass this pointer to modals / navigations view controllers it creates.
This controller start observing User's location changes in their viewDidLoad and react accordingly.
- (void)viewDidLoad {
[self observeValueForKeyPath:#"location" ofObject:self.user change:0 context:NULL];
}
Your view controller would also register for notification raised by your location services objects to display an alert to the user.
Based on other answers:
there is no real penalty to create multiple CLLocationManager instances in your code. The only side effect is that the api is asynchronous, thus you have to wait to get a valid location in your view controller. You can try to get the current location from the location manager on your viewDidLoad using locationManager.location API.
don't share stuff from your app delegate. This prevent code reuse. What if you reuse your views and you app delegate don't have a location manager ?
if you need more code, please ask.
I have a Map View defined in IB and it is set to show the user location.
In my app, in -viewDidAppear, I query self.mapView.userLocation.location.coordinate and it comes back with insane values such as:
latitude: 4.8194501961644877e-49
longitude: 2.2993313035571993e-59
However, the next time -viewDidAppear is called (after I've simply moved to another tabbed view and then back to this one) the userLocation property holds exactly the correct values for my current location.
It seems that at the time of my initial call, the userLocation property has not been initialised but despite having read Apple's documentation I can't see any caveats where it says that this property is only valid after doing xxx.
Is there something that has to happen before userLocation is valid to use or should I just use CLLocationManager and ask it instead?
Thanks in advance for any help.
Sadly, Thomas' suggestion didn't help. What I have since discovered is:
If showsUserLocation is NO, then userLocation is never set correctly and -MapView:didUpdateUserLocation: is never called, consequently I never ever get a sensible location value.
So, to get the user's location I have to set showsUserLocation to YES, however that then means that after all my annotations have been added to the view (without including the user's location) I then calculate the required span to encompass them all and display them all at the right zoom level. After I do that though, the view jumps sideways as the Map View then automatically displays the user's location as the blue blob! As it was never included in the annotations to work out the zoom level I can't incorporate it into my calculations. Aaargh!
Note that when showsUserLocation is YES, then -MapView:didUpdateUserLocation: is called, but only after I've calculated all the coordinates of my annotations, not before!
I'm assuming it hasn't finished finding the user location - it has to work this out and it may take a while.
Instead of using it in viewDidLoad use THIS delegate method:
- (void)mapView:(MKMapView *)myMapView didUpdateUserLocation:(MKUserLocation *)userLocation;
You will need to set your mapview delegate to self. :)
Same is often true of Core Location. You'll get the last location lingering it its buffer, sometimes, or a super-broad throw-the-dart-at-the-map kind of location...
Best bet is to check the .horizontalAccuracy property of the location object and toss any that are too vague. It's good practice to just chuck the first one too.
for didUpdateUserLocation to be called you have to have...
mapView.showsUserLocation = TRUE;
I'm a newb to iphone development and objective c, but hoping some folks smarter than me can lend a hand. Here's my problem:
I have a view based app with about 7 different view controllers. The user navigates via a bottom tab bar. I have the users entering data in the first view controller to an object named "copies". I need to get the copies value to another controller so it can be used for calculations. This needs to be done for many objects in the apps other controllers too.
Example:
User enters Copies value in 1st view controller.
User enters Price value in 6th view controller.
7th view controller calculates copies x price = grand total
In my research I worked out the singleton method, but that seems limited to static data.
What's the best way to ensure that another view controller can access an object the user has filled in? I'm trying to avoid going a SQLite route currently. I want to stick to something basic and work my way up in complexity. Does anyone have any sample code I can review? It really helps to see how others have tackled this before.
Thanks in advance!
If I've understood you correctly there is just one copies value and one price value in the whole app. If that is the case...
There are many ways to do this. Easiest way (perhaps): you could make a Singleton object of a class that you define that has copies and price as properties. Singleton in Objective-C is here, and you would define your properties within the Singleton class. Then you would just call its shared instance and use the values on that. So your code would look like this:
[ThatCrazySingleton sharedInstance].copies = 5;
for writing.
Hope this is what you're looking for.
If you don't want to use a Singleton, at some point one of the UIViewControllers would need to send a message to the others with the copies and price values (hopefully wrapped up ["encapsulated"] in an object). This means that you have to get a reference to the other View controllers, which you can always do by going through the hierarchy.
i'm new here,
i'm new in iphone development,
i'm new in Objective-c
and i'm new in engligh speaking, so don't hate me :P
I'm creating an application that will use the location manager to display the distance between the own position and the positions of a list of shops, like AroundME.
Now, i give the locationManager property to my main class and in the .m of that class, precisely in the viewDidLoad method, i make: [locationManager startUpdatingLocation].
It all works fine, but the problem is:
i need to know my position in other classes than the main, but i don't think that is a good idea making [locationManager startUpdatingLocation] every time i need it, is not time overhead?
The view of my main class is always below the others, so can i retrieve the updated location in my other classes? In what way?
Creating another instance of my main class is not useful, i think, but the locationManager, once started, doesn't stop until my main class is released, isn't true? So i think that it is accessible in some way.
Thanks for your attention and sorry for my awful english : )
I'm going to assume that you set your main class as the CLLocationManagerDelegate in this case. Your delegate will receive locationManager:didUpdateToLocation:fromLocation: messages when the location is updated and in that method you can use NSNotificationCenter to post messages which instances of other classes can add themselves as observers for. See the documentation for NSNotificationCenter for more info on adding observers and posting notifications.
To get the initial location in other classes besides main, you'll probably have to have a reference to the main class and retrieve it using the location property of CLLocationManager because your observers will only receive notifications when the location has changed.
I want to use a MKMapView to display the user current location using the default breathing blue pin and I want to record the user movement at the same time. Is there any way that I could use the GPS manager (not sure if this is a CLLocationManager) the MKMapView uses when we enabled it to show user location?
I know that I can create my own CLLocationManager. But this feels like adding an overhead to my application and I would like the map and my tracking to remain in sync.
I already explored the following ideas without success:
Use the [MKMapView showUserLocation:YES] and add KVO on the userLocation field. This does not work and I am wondering if this is due to the fact that the userLocation field is read only.
Use the [MKMapView showUserLocation:YES], create a MKMapViewDelegate and add the tracking when the annotation view for the user location is requested. This does not work, because the annotation view is apparently requested only once???
Use a CLLocationManager and try to add the blue pin manually. Unfortunately, I did not find the blue pin in the available pin types, so I tried to create a user annotation manually without success.
Does anyone has any idea how I can achieve this and still benefit from the blue pin or is my only solution to use a CLLocationManager and create my own pin?
CLLocationManager uses the same data across all of its instances. MKMapView uses CLLocationManager's data internally. That said the solution to do what you want to do is let MKMapView do its own thing with regards to showUserLocation:. At the same time, create an instance of CLLocationManager and its delegate.
The delegate messages will give you the GPS coordinate location of MKMapView's blue pin. Everything will be in sync with each other.