Question

I have an app that uses a GoogleMap view.
Into that app, I want to display some custom anotations, and a custom view for the userLocation. When the location manager gives a heading, I want to display that custom view for userLocation, if it fails to deliver one, I want the default blue animated dot to come back, etc…

Project and Source code available HERE

Well, there are 2 problems here :

1st problem, THE REALLY BAD ONE. You can play for hours with that tiny app. But… Launch it, wait it loads, send it to the background, put your iPhone in sleep mode, wait a minute, wake up your iPhone, launch the app (that wakes it up) : crash, EXC_BAD_ACCESS. Do the same thing not putting the iPhone in sleep mode : no crash. Not waiting for a minute but a few seconds, no crash. 10 seconds, no crash, 20 seconds, no crash, nears 30 seconds, perhaps a crash, near a minute, crash !

2nd problem (bonus 🙂 ), that can be linked with the first one, but that is not really the heart of this question : the solution I use to achieve the userPinLocation to update from/to the blue pin seems to have a really bad side effect : the userLocation does not move on the map as you move in the street. For any answer for that 2nd problem, if it’s not directly linked with the crash, please use comments not answers. This is not the heart of the question… I think…

To find the faulty code, I’ve reduced my app at its minimum. That gives the following code (some tips in the source code as comments) :

EXC_BAD_ACCESS_TestViewController.h

#import <MapKit/MapKit.h>

@interface EXC_BAD_ACCESS_TestViewController : UIViewController<CLLocationManagerDelegate> {

    CLLocationManager* locationMgr;
    NSMutableArray* customAnnotations;
    CLLocationDirection userHeading;
    MKMapView* myMapView;
}

@property(nonatomic, retain) CLLocationManager* locationMgr;
@property(nonatomic, retain) NSMutableArray* customAnnotations;
@property(nonatomic, assign) CLLocationDirection userHeading;
@property(nonatomic, retain) IBOutlet MKMapView* myMapView;

- (void) loadAnnotations;

@end

EXC_BAD_ACCESS_TestViewController.m

// On first launch, due to code simplification, the app may crash when asked authorization to use geo hardware. Just kill/relaunch after accepting.
// Breakpoints on each method entry : EXC_BAD_ACCESS crash without any break-stop

#import "EXC_BAD_ACCESS_TestViewController.h"
#import "CustomAnnotation.h"

@implementation EXC_BAD_ACCESS_TestViewController

@synthesize locationMgr, customAnnotations, myMapView, userHeading;

// ===========================================================================================================
-(id) initWithCoder:(NSCoder *)aDecoder
{
    self = [super initWithCoder:aDecoder];
    if (!self) return nil;

    self.userHeading = -1;

    return self;
}

// ===========================================================================================================
- (void) viewDidLoad
{
    [self loadAnnotations];

    self.myMapView.mapType = MKMapTypeStandard;
    self.myMapView.showsUserLocation = YES;

    // -----------------------------------------------
    // Just comment this sole line : no more crash
    // -----------------------------------------------
    for (CustomAnnotation* pin in self.customAnnotations) [self.myMapView addAnnotation:pin];

    // locationManager
    self.locationMgr = [[CLLocationManager alloc] init];
    self.locationMgr.desiredAccuracy = kCLLocationAccuracyBest;
    self.locationMgr.distanceFilter = 1.0;
    self.locationMgr.headingFilter = 1.0;
    self.locationMgr.purpose = @"Some purpose.";
    self.locationMgr.delegate = self;
    [self.locationMgr startUpdatingHeading];

    [super viewDidLoad];
}

// ===========================================================================================================
- (void) loadAnnotations
{   
    // Code for testing, real code gets the datas using another way of doing, as simple as this one
    self.customAnnotations = [NSMutableArray array];
    double latitude = 45.0;
    double longitude = -45.0;

    for (int i=1; i<=400; i++) {
        CLLocationCoordinate2D pinLocation = CLLocationCoordinate2DMake(latitude, longitude);
        CustomAnnotation* pin = [[[CustomAnnotation alloc] initWithCoordinate:pinLocation] autorelease];            
        [self.customAnnotations addObject:pin];

        latitude += 0.01;
        longitude += 0.01;
    }
}

// ===========================================================================================================
- (MKAnnotationView *) mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>) annotation
{
    MKAnnotationView* pinView = nil;
    NSString* annotationIdentifier;
    UIImage* pinImage;
    BOOL canShowCallout;

    // User location
    if ([annotation isKindOfClass:[MKUserLocation class]] && self.userHeading >= 0) {
        annotationIdentifier = @"UserLocationAnnotation";
        pinImage = [UIImage imageNamed:@"custom_userlocation.png"];
        canShowCallout = NO;
    }
    // Custom Pin
    else if ([annotation isKindOfClass:[CustomAnnotation class]]) {
        annotationIdentifier = @"CustomAnnotation";
        pinImage = [UIImage imageNamed:@"custom_pin.png"];
        canShowCallout = YES;
    }
    // Others
    else {
        return nil;
    }

    pinView = (MKAnnotationView*)[mapView dequeueReusableAnnotationViewWithIdentifier:annotationIdentifier];

    if (pinView) {
        pinView.annotation = annotation;
    }
    else {
        pinView = [[[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:annotationIdentifier] autorelease];
        if (pinView) {
            pinView.image = pinImage;
            pinView.canShowCallout = canShowCallout;

            if (canShowCallout) {
                pinView.calloutOffset = CGPointMake(-5, 5);
                pinView.rightCalloutAccessoryView = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
            }
        }
    }

    return pinView;
}

// -----------------------------------------------
// Just comment this method : no more crash
// -----------------------------------------------
// ===========================================================================================================
- (void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading
{
    if (!self.myMapView) return;
    if (!self.myMapView.userLocation) return;

    CLLocationDirection compassHeading_True = newHeading.trueHeading;
    CLLocationDirection compassHeading_Magnetic = newHeading.magneticHeading;

    CLLocationDirection heading;
    if (compassHeading_True == -1)              heading = compassHeading_Magnetic;
    else if (newHeading.headingAccuracy >= 0)   heading = compassHeading_True;
    else                                        heading = -1;

    // If we get/loose the heading, update pin image
    // I didn't found any other solution to force the user pin to update its display.
    if ((self.userHeading == -1 || heading == -1) && self.userHeading != heading) {
        [self.myMapView removeAnnotation:self.myMapView.userLocation];
        self.userHeading = heading;
        [self.myMapView addAnnotation:self.myMapView.userLocation];
    }

    self.userHeading = heading;

    // ------------------------------------
    // Some non bugued code was there
    // ------------------------------------
}

// ===========================================================================================================
- (void) dealloc
{   
    self.myMapView = nil;
    self.customAnnotations = nil;
    self.locationMgr = nil;

    [super dealloc];
}

@end

CustomAnnotation.h

#import <MapKit/MapKit.h>

@interface CustomAnnotation : NSObject<MKAnnotation> {
    CLLocationCoordinate2D coordinate;
}

@property(nonatomic, assign) CLLocationCoordinate2D coordinate;

- (id)initWithCoordinate:(CLLocationCoordinate2D) c;
@end

CustomAnnotation.m

#import "CustomAnnotation.h"

@implementation CustomAnnotation

@synthesize coordinate;

// ===========================================================================================================
- (id)initWithCoordinate:(CLLocationCoordinate2D) c
{
    self = [super init];
    if (!self) return nil;

    self.coordinate = c;

    return self;
}

// ===========================================================================================================
- (NSString*)subtitle 
{
    return @"";
}

// ===========================================================================================================
- (NSString*)title 
{
    return @"";
}

@end

I tried breakpoints in each methods, trying to enable Zombies with environment variables (but as this needs to be ran on the device, I’m not sure they’ve been really activated), without any start of solution… I still don’t have any idea of what’s going wrong.

Do you see how to solve that EXC_BAD_ACCESS problem ?
For any answer for the 2nd problem, please use comments and not answers if it don’t solve the crash. This problem is not the heart of the question as far as I’ve seen.

Tip : I’ve put 2 comments in the code above where I found some start of solution. There are 2 places, that does not seems connected, that can be put out of the code one OR the other to solve the problem. What makes me crazy is the OR.

Runned on an iPhone 4 ios 4.2.1

Answer 1

[self.myMapView removeAnnotation:self.myMapView.userLocation];

This line is causing the crash from stacktrace this is what I’ve seen.

When I saw exc_bad_access I did a bt in gdb. I have added Guard Malloc breakpoint. Looking at the stack it said about removing annotation.