Is it possible to start / stop location updates from the UI of the iphone? All I need from the app is to show me my location unless I click "stop" and then "start" again.
I can't seem to be able to do that...I have my location displayed properly, and I also created two IBButtons and created a function for each of them, however, my app crashes when I click on each one of those buttons. I placed those functions under the viewcontroller.m.
I am kind of new to this, so any help would be appreciated. Thanks!
(IBAction)startUpdating: (CLLocation *)location
{
[location startUpdatingLocation];
}
(IBAction)stopUpdating: (CLLocation *)location
{
[location stopUpdatingLocation];
}
start/stopUpdatingLocation are CLLocationManager instance methods, rather than CLLocation instance methods... so create a CLLocationManager instance.
.h
#interface someClass:somesuperclass{
CLLocationManager * locationManager;
BOOL updating;
}
-(IBAction)toggleUpdating:(id)sender;
#end
.m somewhere in the view load/ or init cycle:
-(void)viewDidLoad{
[super viewDidLoad];
locationManager = [[CLLocationManager alloc] init];
}
-(void)viewDidUnload{
[locationManager stopUpdatingLocation];
[locationManager release];
[super viewDidUnload];
}
-(IBAction)toggleUpdating:(id)sender
{
if(!updating)
{
[locationManager startUpdatingLocation];
}else{
[locationManager stopUpdatingLocation];
}
updating = !updating;
}
also your action above will never work, because the thing after a colon in an action will be the object that sent the action, a UIButton in your case.
Related
I am trying to get the compass of the iphone to work using the rhomobile framework.
I already did the rhomobile part, created a working wrapper that calls native methods on the iphone, but I cant manage to get the events to work.
Locationmanager.h
#import <UIKit/UIKit.h>
#import <CoreLocation/CoreLocation.h>
#interface locationController : NSObject <CLLocationManagerDelegate>
{
CLLocationManager *locationManager;
}
#property (strong, nonatomic) CLLocationManager *locationManager;
- (id)init;
- (void)dealloc;
#end
Locationmanager.m
#import "Locationmanager.h"
#include "ruby/ext/rho/rhoruby.h"
//store the values
double gx, gy, gz, gth;
//init location
locationController *lc;
#implementation locationController
#synthesize locationManager;
- (id)init {
if (self = [super init]) {
self.locationManager = [[CLLocationManager alloc] init];
NSLog(#"%#", [CLLocationManager headingAvailable]? #"\n\nHeading available!\n" : #"\n\nNo heading..\n");
NSLog(#"%#", [CLLocationManager locationServicesEnabled]? #"\n\nLocation available!\n" : #"\n\nNo location..\n");
// check if the hardware has a compass
if ([CLLocationManager headingAvailable] == NO) {
// No compass is available. This application cannot function without a compass,
// so a dialog will be displayed and no magnetic data will be measured.
locationManager = nil;
UIAlertView *noCompassAlert = [[UIAlertView alloc] initWithTitle:#"No Compass!" message:#"This device does not have the ability to measure magnetic fields." delegate:nil cancelButtonTitle:#"OK" otherButtonTitles:nil];
[noCompassAlert show];
[noCompassAlert release];
NSLog(#"\n***** ERROR *****\n No compass found !!!");
} else {
// setup delegate callbacks
locationManager.delegate = self;
// heading service configuration
locationManager.headingFilter = kCLHeadingFilterNone;
// location service configuration
locationManager.distanceFilter = kCLDistanceFilterNone;
locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters;
//start location services
[locationManager startUpdatingLocation];
// start the compass
[locationManager startUpdatingHeading];
}
return self;
}
}
- (void)dealloc {
[super dealloc];
// Stop the compass
[locationManager stopUpdatingHeading];
[locationManager release];
}
// This delegate method is invoked when the location manager has heading data.
- (void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)heading {
NSLog(#"\n\n***** New magnetic heading *****\n %f\n", heading.magneticHeading);
NSLog(#"\n\n***** New true heading *****\n %f\n", heading.trueHeading);
gx = heading.x;
gy = heading.y;
gz = heading.z;
gth = heading.trueHeading;
}
// This delegate method is invoked when the location managed encounters an error condition.
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error {
if ([error code] == kCLErrorDenied) {
// This error indicates that the user has denied the application's request to use location services.
NSLog(#"\n ***** ERROR *****\n Location not allowed!");
[locationManager stopUpdatingHeading];
} else if ([error code] == kCLErrorHeadingFailure) {
NSLog(#"\n ***** ERROR *****\n Magnetic interference or something!");
}
}
#end
//ruby wrappers
void locationmanager_init(void) {
// make sure we can only start this method once
static bool started = false;
if(!started) {
// Initialize the Objective C accelerometer class.
lc = [[locationController alloc] init];
started = true;
}
}
void locationmanager_get_heading(double *x, double *y, double *z, double *th) {
NSLog(#"\n ***** DEBUGGER *****\n Getting heading x: %f, y: %f, z: %f, heading: %f", gx, gy, gz, gth);
*x = gx;
*y = gy;
*z = gz;
*th = gth;
}
I'm running the code on an iphone 4 with iOS 5.1, in the console I can see the debug messages of init, but I never see a debug message of the didUpdateHeading delegate. Anyone got a clue what I missed here?
UPDATE
I think I need to run my code in a background thread to get it working. Currently the locationmanager_init initializes + leaves the code, therefor its not active and the events are not fired.
Anyone got a simple solution initializing this in the background to keep it active?
UPDATE 2
Returned the id, used self = [super init] and still no fix :(
GitHub code
Initializes with locationmanager_init, retrieves data with locationmanager_get_heading
You have to init the CLLocationManager on the main thread, check this SO here, or run it from a thread with an active run loop, check this SO here, From Apple documentation:
Configuration of your location manager object must always occur on a thread with
an active run loop, such as your application’s main thread.
Make sure your locationController and the CCLocationManager inside it are alive past initialization, check here. I may be wrong here, but from your Github code, it seems that the *lc variable is getting released in the autorelease pool. Try giving it an extra retain.
lc = [[[locationController alloc] init] retain];
I guess this is the cause of your problem. If the object is released you wont get any updates.
Not related to the question but:
You should call [super dealloc] last but not first, check this SO here
Put the return statement in your init method before the last parenthesis, and not before the second last.
...
// start the compass
[locationManager startUpdatingHeading];
}
}
return self;
}
- (void)locationManager:(CLLocationManager *)manager
didUpdateHeading:(CLHeading *)heading;
- (void)locationManager:(CLLocationManager *)manager
didFailWithError:(NSError *)error;
These are your instance methods not delegate methods.
check
https://developer.apple.com/library/mac/#documentation/CoreLocation/Reference/CLLocationManagerDelegate_Protocol/CLLocationManagerDelegate/CLLocationManagerDelegate.html
Possibly this is not the solution to the overall problem, but your init method is missing a return statement:
- (id)init {
if (self = [super init]) {
// do your setup here
}
return self;
}
Currently, developing an app that needs to get last location from CLLocationManager (without any regular tracking). It doesn't matter how old, accurate it is. I don't need and want to start tracking - I just need to just grab some last location from a cache and that's it. IMHO, CLLocationManager is a shared component in iOS and if some app uses location tracking then another app should be able to use the most recent location from CLLocationManager.location. It should be sufficient just to alloc/init CLLocationManager and grab its location. However it's not. I have tested on iPhone4 - started google maps, saw my current location, then went to my app, but after [[CLLocationManager alloc] init] location property is nil.
UPDATE: tried [locationManager startUpdatingLocation]; and [locationManager stopUpdatingLocation]; but the result is the same. I guess, the only solution is to start regular tracking?
UPDATE2: Strange but there's no alert with "The app wants to use location services" after alloc/init of CLLocationManager. Here's my code fragment:
CLLocationManager *locationManager = [[CLLocationManager alloc] init];
[locationManager startUpdatingLocation];
[locationManager stopUpdatingLocation];
NSLog(#"%#", locationManager.location); //prints nil
First you should check if your locationManager has a, let's say, 'static' location pre-saved.
If it does, you're done.
If not, you should startUpdatingLocation and then, in the didUpdateToLocation:fromLocation: callback, stopUpdatingLocation once you get the location.
My experience says that's the best way to get only one location.
UPDATE TO MATCH AUTHOR UPDATES:
You should not stopUpdatingLocation just after startUpdatingLocation. startUpdatingLocation starts a service in background, so you should wait until you get a location, so invoque it in the callback methods.
To make any use of CLLocationManager you need to implement CLLocationManagerDelegate somewhere.
-[CLLocationManager startUpdatingLocation] starts an async process. If you stop it in the same runloop cycle the process never gets started and that is the reason you never see the permission dialog.
It goes something like this:
#interface MyClass : NSObject <CLLocationManagerDelegate> {
CLLocationManager *manager;
CLLocation *lastLocation;
}
#end
#implementation
- (id)init {
self = [super init];
if (self) {
manager = [[CLLocationManager alloc] init];
manager.delegate = self;
[manager startUpdatingLocation];
}
return self;
}
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation;
{
lastLocation = newLocation;
[manager stopUpdatingLocation];
}
// in your real implementation be sure to handle the error cases as well.
#end
I am trying to connect to GPS from my code. I am doing so according to this tutorial.
- (void)viewDidLoad {
[super viewDidLoad];
CLController = [[CoreLocationController alloc] init];
CLController.delegate = self;
[CLController.locMgr startUpdatingLocation];
}
- (void)locationUpdate:(CLLocation *)location {
locLabel.text = [location description];
}
- (void)locationError:(NSError *)error {
locLabel.text = [error description];
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
}
The above code is placed in a view controller called GetMyLocationViewController, and I have another view controller called MainScreenViewController.
When the screen loads, the MainScreenViewController gets loaded, and I will need the GPS location to continue operations with this screen.
In the ViewDidLoad method of MainScreenViewController I wrote the following;
- (void)viewDidLoad {
[super viewDidLoad];
GetMyLocationViewController *getMyLocationViewController = [[GetMyLocationViewController alloc]initwithXib:nil bundle:nil];
[self.navigationController pushViewController:getMyLocationViewController Animation:YES];
// AND THEN I NEED TO ACCESS THE LONGITUDE AND LATITUDE VALUES
}
When the above code gets executed, the viewDidLoad method of MainScreenViewController gets executed, but not the locationUpdate method. The only way I could get the values of longitude and latitude is by the execution of locationUpdate method. So how can I get these values?
Do you tested in a device? xcode before the version 4.2 dont have a GPS simulator, because of that the method locationUpdate never call.
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
if([self.delegate conformsToProtocol:#protocol(CoreLocationControllerDelegate)]) { // Check if the class assigning itself as the delegate conforms to our protocol. If not, the message will go nowhere. Not good.
[self.delegate locationUpdate:newLocation];
}
}
Are you sure you are loading your GetMyLocationViewController? Your code only shows loading the MainScreenViewController, which, in its -viewDidLoad method, loads itself again, which would cause an infinite loop of loading and pushing MainScreenViewControllers.
UPDATE: That CoreLocationController class in the tutorial seems unnecessary. Rather that using it, make CLLocationManager a property of your GetMyLocationViewController. Make GetMyLocationViewController's -viewDidLoad method look like this:
-(void)viewDidLoad {
[super viewDidLoad];
self.locationManager = [[CLLocationManager alloc] init];
self.locationManager.delegate = self;
[self.locationManager startUpdatingLocation];
}
don't forget to import the CoreLocation library and implement the delegate methods.
I am trying to tweak my CLLocationManager settings so that when I call startUpdatingLocation it calls the delegate right away. Any idea on how to do this?
Thats not possible. The reason is simple, the device has no position fix that matches your desired accuracy the whole time. It might have to turn on the GPS chip to do this which also takes some time to ge a location (without additional infos and an outdated almanac this might take up to 15 minutes in the worst case).
It's not possible to tweak CLLocationManger in that way. However, what you could do is writing a wrapper around CLLocationManager which obtains the current position on startup and returns it everytime you ask for it. However, there might be situations where the location is not (yet) available, and this approach is quite power-consuming as you are using the GPS-device all the time.
This is by far NOT the best way (not even a good way probably) to use a CLLocationManager and when I find the time I am planning on going back and changing my code to only have a single CLLocationManager within my AppDelegate and have all sub view controller call the AppDelegate for their location needs.
I have the following code in a view controller (not the main controller or app delegate either), and about 5-10 seconds after the view controller is pushed by my main views navigation controller, it starts writing to NSLog with an accurate long/lat of my position (i.e. the delegate method locationManager:didUpdateToLocation:fromLocation: starts getting called):
- (void)viewDidLoad {
[super viewDidLoad];
// ....
self.locationManager = [[[CLLocationManager alloc] init] autorelease];
[locationManager setDelegate:self];
[locationManager setDesiredAccuracy:kCLLocationAccuracyBest];
[locationManager setDistanceFilter:kCLDistanceFilterNone];
[locationManager startUpdatingLocation];
// ....
}
// This will be called just a few seconds after the view appears and the
// location is accurate (if I have location services on and good sky-line of sight)
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
NSDate* eventDate = newLocation.timestamp;
NSTimeInterval howRecent = [eventDate timeIntervalSinceNow];
if (abs(howRecent) < 5.0) {
self.latitude = [NSNumber numberWithDouble:newLocation.coordinate.latitude];
self.longitude = [NSNumber numberWithDouble:newLocation.coordinate.longitude];
NSLog(#"New Latitude %+.6f, Longitude %+.6f", newLocation.coordinate.latitude, newLocation.coordinate.longitude);
}
}
// Then, tear down the location Manager (so I can use it in another view controller)
// A bit excessive possibly, but I like to be absolutely sure that my App does not use the GPS
// when it doesn't need it to save batter life.
- (void)viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
[locationManager stopMonitoringSignificantLocationChanges];
[locationManager stopUpdatingHeading];
[locationManager stopUpdatingLocation];
}
- (void)viewDidDisappear:(BOOL)animated {
[super viewDidDisappear:animated];
[locationManager stopMonitoringSignificantLocationChanges];
[locationManager stopUpdatingHeading];
[locationManager stopUpdatingLocation];
}
- (void)viewDidUnload {
[locationManager stopUpdatingLocation];
[locationManager stopMonitoringSignificantLocationChanges];
[locationManager stopUpdatingHeading];
[locationManager setDelegate:nil];
self.locationManager = nil;
}
- (void)dealloc {
// ....
[locationManager stopUpdatingLocation];
[locationManager setDelegate:nil];
[locationManager release], locationManager = nil;
// ....
[super dealloc];
}
Then, in places like actionSheet:clickedButtonAtIndex:, I can get the location values on0demand with locationManager.location.coordinate.latitude / locationManager.location.coordinate.longitude or self.latitude / self.longitude.
This might be one of those silly question where, once a solution is pointed out, makes you feel pretty stupid wondering how you didn't see it but I can't figure out why this part of my app is crashing with EXC_BAD_ACCESS (and no stack trace).
I have a CLLocationManager *locationManager (ivar declared in interface file) that gets created on viewDidLoad if locationServices is enabled:
- (void)viewDidLoad
{
[super viewDidLoad];
if ([CLLocationManager locationServicesEnabled])
[self findUserLocation];
...
}
#pragma mark - Location finder methods
- (void)findUserLocation
{
locationManager = [[CLLocationManager alloc] init];
locationManager.delegate = self;
locationManager.desiredAccuracy = kCLLocationAccuracyThreeKilometers;
[locationManager startUpdatingLocation];
}
So the location manager starts updating location and each time and update is found, the delegate method below is called, where I check to see if I should time out or continue looking for my desiredAccuracy:
#pragma mark - CLLocationManager delegates
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
if ([newLocation.timestamp timeIntervalSinceDate:oldLocation.timestamp] > 8)
[self locationManagerTimeOut];
else if ((newLocation.horizontalAccuracy <= manager.desiredAccuracy) && (newLocation.verticalAccuracy <= manager.desiredAccuracy))
[self locationManagerLockedPosition];
}
If a position is locked, this method is called:
- (void)locationManagerLockedPosition
{
[locationManager stopUpdatingLocation];
locationManager.delegate = nil;
[locationManager release], locationManager = nil;
NSLog (#"add results to view");
}
If it times out, this is the method called:
- (void)locationManagerTimeOut
{
[locationManager stopUpdatingLocation];
locationManager.delegate = nil;
[locationManager release], locationManager = nil;
NSLog (#"Time out!");
}
Problem is, in either case (time out or locked position), I get the NSLog output in the console and then 2 secs later the app crashes??
Interesting thing is, if I comment out my [locationManager release]... line, everything works fine but WHY? Also if I move the [locationManager release] to my dealloc method, no crashes either!
Am I missing something basic here?
Thanks!
Rog
I had the same issue and there's probably some problem in the depths of CLLocationManager. Fixed by doing:
[locationManager stopUpdatingLocation];
[self performSelector:#selector(discardLocationManager) onThread:[NSThread currentThread] withObject:nil waitUntilDone:NO];
and in discardLocationManager do:
- (void) discardLocationManager
{
locationManager.delegate = nil;
[locationManager release];
}
You are release the CLLocationManager instance from within a callback method, which can't be a good idea.
The CLLocationManager calls your callbacks locationManager:didUpdateToLocation:fromLocation etc. If you release the location manager instance, you're basically deallocating the object that just called you. Bad idea. That's why the app crashes.
Instead of releasing the location manager instance, you could autorelease it.
Sargon