Stop iOS 7 MKMapView from leaking memory

Question

I've noticed that my app leaks memory, but if I take the MKMapView out the memory problem goes away.

To test the theory, I made a dead simple project that has a view that pushes a view with a MKMapView in it and pops and pushes. Nothing more. No code in the view controllers, everthing done via storyboard.

If I go back and forth to the map view, it starts about 3MB after doing pushing and popping the view with the map in it this about 15 times the memory is around 230MB.

Anyone else seen this? Seems like a pretty big bug. Is there a different way to use MKMapView that will prevent it from leaking so much?

Answer 1

I had faced the same issue and (thanks to Stackoverflow) fixed it by changing MKMapType in viewWillDisappear and deallocating/setting its delegate to nil.As it still sends message to delegates. This is documented in MKMapViewDelegate Protocol Reference:

Before releasing an MKMapView object for which you have set a delegate, remember to set that object’s delegate property to nil. One place you can do this is in the dealloc method where you dispose of the map view

.

-(void)viewWillDisappear:(BOOL)animated{
  [super viewWillDisappear:animated];
  [self applyMapViewMemoryFix];

}

- (void)applyMapViewMemoryFix{

switch (self.mkMapView.mapType) {
    case MKMapTypeHybrid:
    {
        self.mkMapView.mapType = MKMapTypeStandard;
    }

        break;
    case MKMapTypeStandard:
    {
        self.mkMapView.mapType = MKMapTypeHybrid;
    }

        break;
    default:
        break;
}
self.mkMapView.showsUserLocation = NO;
self.mkMapView.delegate = nil;
[self.mkMapView removeFromSuperview];
self.mkMapView = nil;
}

hope this helps

Answer 2

Swift Version:

override func viewWillDisappear(_ animated:Bool) {
    super.viewWillDisappear(animated)
    self.applyMapViewMemoryFix()
}

func applyMapViewMemoryFix() {
    switch (self.mapView.mapType) {
    case MKMapType.hybrid:
        self.mapView.mapType = MKMapType.standard
    case MKMapType.standard:
        self.mapView.mapType = MKMapType.hybrid
    default:
        break
    }
    self.mapView.showsUserLocation = false
    self.mapView.delegate = nil
    self.mapView.removeFromSuperview()
    self.mapView = nil
}

Answer 3

The best solution I have found is to have an instance of MKMapView in your delegate, you will allocate it only once.

Then anytime you need a MapView, you just use the one from the delegate.

In my case i needed to clean the annotations from it as soon as the view willDisappear ( to not have older annotations on the map ).

  - (void)viewDidLoad {
      AppDelegate *delegate = [UIApplication sharedApplication].delegate;
          if (!delegate.appModel.mapView)
             delegate.appModel.mapView = [[MKMapView alloc] initWithFrame:self.view.frame];
      self.mapView = delegate.appModel.mapView;
      [self.mapView setFrame:self.view.frame];
      [self.mapView setDelegate:self];
      [self.view addSubview:self.mapView];
   }

- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];
    [self.mapView removeAnnotations:self.mapView.annotations];
    for (id<MKOverlay> overlay in self.mapView.overlays) {
        [self.mapView removeOverlay:overlay];
    }
}