I have been struggling with this for long. I read many resources but still not able to find a clear way around it.
I have a Sqlite table with rows of latitudes and longitudes. My task is to fetch those latitudes and longitudes and put them in an array and then use later for displaying on map with all the pins. I do these "reading from database" in my AppDelegate (is this advisable or is it better to do in view controller which has the map?)
I fetch the lat and long as double values as shown below
while (sqlite3_step(selectStmt)==SQLITE_ROW){
double latitude= sqlite3_column_double(selectStmt, 1);
double longitude= sqlite3_column_double(selectStmt, 2);
CLLocationCoordinate2D coord=CLLocationCoordinate2DMake(latitude,longitude);
// I want to add this to an array, so that i can use later for annotations
}
However when i try to add "Incompatible type for argument 1 off addObject".
Is this the right way of fetching multiple coordinates from sqlite to display on maps?
Help would be appreciated
You need to use CLLocation class to store your location data.
http://developer.apple.com/library/ios/#DOCUMENTATION/CoreLocation/Reference/CLLocation_Class/CLLocation/CLLocation.html#//apple_ref/doc/uid/TP40007126
CLLocation *location = [[CLLocation alloc] initWithLatitude:latitude longitude:longitude];
[array addObject:location];
[location release];
CLLocationCoordinate2D is a struct not an object and you need objects for addObject methods.
You can use the CLLocation as Evgeniy suggest or create your own object to store/retrieve those values.
Related
I need to display a MKMapView with more than 4 locations with different Annotations and a route connecting the locations. I have tried to display the multiple locations inside a MKMapView but i still not able to find out on how to connect the locations with a route. I am also trying to get this checked if i have implemented it in a right way. I have created a "CLLocationCoordinate2D" and then added a lat and long similarly for 4 points. I have created a custom object which implements MKAnnotation and returning a location .
CLLocationCoordinate2D coordinate1 = CLLocationCoordinate2DMake(40.7180583 ,-74.007109);
CLLocationCoordinate2D coordinate2 = CLLocationCoordinate2DMake(40.716355 ,-74.006816);
CLLocationCoordinate2D coordinate3 = CLLocationCoordinate2DMake(40.715281 ,-74.005485);
CLLocationCoordinate2D coordinate4 = CLLocationCoordinate2DMake(40.71559 ,-74.003114);
AnnotationPoints *location1 = [[AnnotationPoints alloc] initWithCoordinate:coordinate1];
AnnotationPoints *location2 = [[AnnotationPoints alloc] initWithCoordinate:coordinate2];
AnnotationPoints *location3 = [[AnnotationPoints alloc] initWithCoordinate:coordinate3];
AnnotationPoints *location4 = [[AnnotationPoints alloc] initWithCoordinate:coordinate4];
NSArray *poiArray = [[NSArray alloc] initWithObjects:location1,location2,location3,location4,nil];
[mapView addAnnotations:poiArray];
//Inside the Annotation Class initWithCoordinate Method is implemented this way:-
-(id)initWithCoordinate:(CLLocationCoordinate2D) c{
coordinate=c;
NSLog(#"%f,%f",c.latitude,c.longitude);
return self;
}
My concern here is i need to create a Annotation Point for every Location. Is there any alternative that i can load all the points at a single place. And another difficulty here is the route connecting all the multiple points. Any help on this? Thanks a lot
The way you are adding the annotations is fine.
Not sure what your concern is and what you mean by "all the points at a single place".
If you want pins/annotations at several places, you have to create a separate annotation object for each place.
Drawing a route connecting those locations requires creating an overlay (not an "annotation").
You want to add an MKPolyline to the map for which you will specify the list of coordinates.
To draw the polyline, you don't need to also add annotations at each coordinate (but you could if you want to).
Creating and adding an MKPolyline and its corresponding MKPolylineView is very similar to MKPolygon and MKPolygonView. See this question for an example:
iPhone MKMapView - MKPolygon Issues
Currently i am working on a Location based application for iPhone/iPad . I have several annotations in my MapKit , what i want to do is to track the location of the user and shows the annotations that are within the 3km . Can somebody give me a start ?
Sorry for the delayed response... the question just fell off my radar.
I'm going to suppose that you have a method that returns a set of NSValue-wrapped CLLocationCoordinate2D structs (the basic approach is the same regardless of what your internal data representations are). You can then filter the list using a method something akin to the following (warning: typed in browser):
NSSet *locations = ...;
CLLocation centerLocation = ...; // Reference location for comparison, maybe from CLLocationManager
CLLocationDistance radius = 3000.; // Radius in meters
NSSet *nearbyLocations = [locations objectsPassingTest:^(id obj, BOOL *stop) {
CLLocationCoordinate2D testCoordinate;
[obj getValue:&testCoordinate];
CLLocation *testLocation = [[CLLocation alloc] initWithLatitude:testCoordinate.latitude
longitude:testCoordinate.longitude];
BOOL returnValue = ([centerLocation distanceFromLocation:testLocation] <= radius);
[testLocation release];
return returnValue;
}
];
With the filtered set of coordinates in hand, you can create MKAnnotation instances and add them to the map in the usual manner, as described in Apple's documentation.
If you have many thousands of test locations then I suppose this approach could start to incur performance issues. You would then want to switch your point storage approach to use, e.g., quadtrees, to reduce the number of points that need to be precision-filtered. But don't optimize prematurely!
Hope that helps!
I'm trying to create then retrieve an array of CLLocationCoordinate2D objects, but for some reason the array is always empty.
I have:
NSMutableArray *currentlyDisplayedTowers;
CLLocationCoordinate2D new_coordinate = { currentTowerLocation.latitude, currentTowerLocation.longitude };
[currentlyDisplayedTowers addObject:[NSData dataWithBytes:&new_coordinate length:sizeof(new_coordinate)] ];
I've also tried this for adding the data:
[currentlyDisplayedTowers addObject:[NSValue value:&new_coordinate withObjCType:#encode(struct CLLocationCoordinate2D)] ];
And either way, the [currentlyDisplayedTowers count] always returns zero. Any ideas what might be going wrong?
Thanks!
To stay in object land, you could create instances of CLLocation and add those to the mutable array.
CLLocation *towerLocation = [[CLLocation alloc] initWithLatitude:lat longitude:lon];
[currentDisplayedTowers addObject:towerLocation];
To get the CLLocationCoordinate struct back from CLLocation, call coordinate on the object.
CLLocationCoordinate2D coord = [[currentDisplayedTowers lastObject] coordinate];
As SB said, make sure your array is allocated and initialized.
You’ll also probably want to use NSValue wrapping as in your second code snippet. Then decoding is as simple as:
NSValue *wrappedCoordinates = [currentlyDisplayedTowers lastObject]; // or whatever object you wish to grab
CLLocationCoordinate2D coordinates;
[wrappedCoordinates getValue:&coordinates];
You need to allocate your array.
NSMutableArray* currentlyDisplayedTowers = [[NSMutableArray alloc] init];
Then you can use it. Be sure to call release when you are done with it or use another factory method.
I had currentlyDisplayedTowers = nil which was causing all the problems. Also, the previous advice to init and alloc were necessary. Thanks everyone for the help!
For anyone else with this issue, there's another solution if you are planning on using MapKit.
(The reason I say IF, of course, is because importing a module such as MapKit purely for a convenient wrapper method is probably not the best move.. but nonetheless here you go.)
#import MapKit;
Then just use MapKit's coordinate value wrapper whenever you need to:
[coordinateArray addObject:[NSValue valueWithMKCoordinate:coordinateToAdd]];
In your example..
[currentlyDisplayedTowers addObject:[NSValue valueWithMKCoordinate:new_coordinate]];
In my app, I am saving coordinates from an MKMapView into a property list. After the user hits "save" I set the center coordinate of the selection view to that on the main view, and then save the mapView.centerCoodinate.latitude and longitude into a pList. However, this gives me a value like "1078114215" which the map says is not a vail coordinate. What am I doing wrong?
Saving a pointer instead of the two floats in the coordinate? Not saving as a float?
Sounds like you're accidentally mis-typing your double variable. When you add it to your dictionary to be stored as a plist be sure to transform it from a double to an NSNumber like this:
[myDictionary addObject:[NSNumber numberWithDouble:latitude] forKey:#"latitude"];
and when you retrieve it, transform it from an NSNumber to a double:
double latitude = [[myDictionary objectForKey:#"latitude"] doubleValue];
I am a new iPhone developer learning Objective-C, and am trying to dynamically calculate the distances between the users latitude/longitude coordinates, with latitude/longitude coordinates in a SQLite table. I know that we can use CLLocations method:
(CLLocationDistance)distanceFromLocation:(const CLLocation *)location
to do this, but I'm not sure how to use it given the data that I have. How does one use the above method using pairs of latitude/longitude coordinates, considering the above method only deals with location objects of type CLLocation? Can anyone give me a simple example of how to use this method using two pairs of latitude/longitude coordinates?
Just create CLLocation objects from your data:
// Assumption: lat1, lon1 and lat2, lon2 are double values containing the coordinates
CLLocation *firstLocation = [[[CLLocation alloc] initWithLatitude:lat1 longitude:lon1] autorelease];
CLLocation *secondLocation = [[[CLLocation alloc] initWithLatitude:lat2 longitude:lon2] autorelease];
CLLocationDistance distance = [secondLocation distanceFromLocation:firstLocation];