多次往返切换初始搜索页与含GMSMapView的地图页后App崩溃求助

Hey there, let's break down why your app is crashing with that NSInternalInconsistencyException related to the camera key path on GMSMapView, and how to fix it.

What's causing this? #

The error message tells us that an -observeValueForKeyPath:ofObject:change:context: message was sent but not handled for the camera property of your map view. This usually happens in two scenarios:

1. You added a manual KVO observer to the map's camera property but forgot to either remove it when your view controller is destroyed, or didn't implement the observer callback properly.
2. Google Maps SDK internal KVO cleanup fails because your GMSMapView isn't being properly deallocated when you navigate away from the map screen (often due to strong reference cycles or not cleaning up the map view properly).

Solutions to try: #

1. Check for manual KVO observers and clean them up

If you explicitly added an observer for the camera key path in your code, you must pair that with removing the observer before your view controller is deallocated.

Swift example:

// If you added this somewhere (like viewDidLoad)
mapView?.addObserver(self, forKeyPath: "camera", options: [.new], context: nil)

// Make sure to remove it in deinit
deinit {
    mapView?.removeObserver(self, forKeyPath: "camera")
}

// And don't forget to implement the observer callback!
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    guard keyPath == "camera", let mapView = object as? GMSMapView else {
        super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
        return
    }
    // Handle camera changes here
}

Objective-C example:

// Adding observer
[_mapView addObserver:self forKeyPath:@"camera" options:NSKeyValueObservingOptionNew context:nil];

// Removing in dealloc
- (void)dealloc {
    [_mapView removeObserver:self forKeyPath:@"camera"];
}

// Implementing the callback
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context {
    if ([keyPath isEqualToString:@"camera"] && object == _mapView) {
        // Handle camera updates
    } else {
        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
    }
}

2. Ensure proper cleanup of GMSMapView when navigating away

If you didn't add any manual KVO observers, the issue is likely that the map view isn't being deallocated correctly. Try these steps:

• Remove the map view from its superview and nil it out when your view disappears. This forces the map view to release its internal resources (including KVO observers):

  override func viewDidDisappear(_ animated: Bool) {
      super.viewDidDisappear(animated)
      mapView?.removeFromSuperview()
      mapView = nil
  }
  

• Check for strong reference cycles: Make sure your view controller doesn't have a strong reference to the map view, and vice versa. For example, if you set mapView.delegate = self, ensure the delegate property is declared as weak (the Google Maps SDK's GMSMapViewDelegate is already weak by default, but double-check if you've made any custom changes).
• Update to the latest Google Maps SDK: Old versions of the SDK had known memory management bugs with KVO. Upgrading to the latest release might resolve the issue automatically.

3. Verify your view controller is being deallocated

If your view controller's deinit (Swift) or dealloc (Objective-C) isn't being called when you pop it from the navigation stack, there's another strong reference holding onto it. Check for:

• Timers that weren't invalidated
• Closures that capture self strongly (use [weak self] or [unowned self] where appropriate)
• Other objects that hold a strong reference to your view controller

Final Notes #

That crash happens because the KVO system is trying to send an update to an observer that either no longer exists or hasn't implemented the required callback. By ensuring proper cleanup of observers and the map view itself, you should be able to eliminate this crash.

内容的提问来源于stack exchange，提问作者Pavan Kumar