Unsubscribe the OnAdLoaded handler when the native ad handler disconnects (#104)

* Unsubscribe the OnAdLoaded handler when the native ad handler disconnects

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Guard the OnAdLoaded unsubscription for pre-created ads

In the NativeAdView(INativeAd, ContentView) path LoadAd never runs, so
_onAdLoaded is null on disconnect. The shipped NativeAd implementations
use field-like events where removing null is a no-op, but INativeAd is
public, so a custom implementation's event accessor could reject null.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: marius-bughiu

src/Plugin.AdMob/Platforms/Android/Native/NativeAdHandler.cs

@@ -13,6 +13,7 @@ internal partial class NativeAdHandler : ViewHandler<NativeAdView, global::Andro
     // The ad outlives the handler on disconnect/reconnect, so the subscriptions
     // made in RegisterEventHandlers must be removed to avoid raising events N times.
     private INativeAd? _registeredAd;
+    private EventHandler? _onAdLoaded;
     private EventHandler<IAdError>? _onAdFailedToLoad;
 
     public static IPropertyMapper<NativeAdView, NativeAdHandler> PropertyMapper =
@@ -77,11 +78,12 @@ private void LoadAd()
         var ad = nativeAdService.CreateAd(adUnitId);
 
         RegisterEventHandlers(ad);
-        ad.OnAdLoaded += (s, e) =>
+        _onAdLoaded = (s, e) =>
         {
             VirtualView.RaiseOnAdLoaded(s, e);
             ShowAd(ad);
         };
+        ad.OnAdLoaded += _onAdLoaded;
 
         ad.Load();
     }
@@ -127,6 +129,11 @@ private void UnregisterEventHandlers()
             return;
         }
 
+        if (_onAdLoaded is not null)
+        {
+            _registeredAd.OnAdLoaded -= _onAdLoaded;
+        }
+
         _registeredAd.OnAdFailedToLoad -= _onAdFailedToLoad;
         _registeredAd.OnAdImpression -= VirtualView.RaiseOnAdImpression;
         _registeredAd.OnAdClicked -= VirtualView.RaiseOnAdClicked;
@@ -135,6 +142,7 @@ private void UnregisterEventHandlers()
         _registeredAd.OnAdClosed -= VirtualView.RaiseOnAdClosed;
 
         _registeredAd = null;
+        _onAdLoaded = null;
         _onAdFailedToLoad = null;
     }
 

src/Plugin.AdMob/Platforms/iOS/Native/NativeAdHandler.cs

@@ -17,6 +17,7 @@ internal partial class NativeAdHandler : ViewHandler<NativeAdView, Google.Mobile
     // The ad outlives the handler on disconnect/reconnect, so the subscriptions
     // made in RegisterEventHandlers must be removed to avoid raising events N times.
     private INativeAd? _registeredAd;
+    private EventHandler? _onAdLoaded;
     private EventHandler<IAdError>? _onAdFailedToLoad;
 
     public static IPropertyMapper<NativeAdView, NativeAdHandler> PropertyMapper
@@ -87,11 +88,12 @@ private void LoadAd()
         var ad = nativeAdService.CreateAd(adUnitId);
 
         RegisterEventHandlers(ad);
-        ad.OnAdLoaded += (s, e) =>
+        _onAdLoaded = (s, e) =>
         {
             VirtualView.RaiseOnAdLoaded(s, e);
             ShowAd(ad);
         };
+        ad.OnAdLoaded += _onAdLoaded;
 
         ad.Load();
     }
@@ -170,6 +172,11 @@ private void UnregisterEventHandlers()
             return;
         }
 
+        if (_onAdLoaded is not null)
+        {
+            _registeredAd.OnAdLoaded -= _onAdLoaded;
+        }
+
         _registeredAd.OnAdFailedToLoad -= _onAdFailedToLoad;
         _registeredAd.OnAdImpression -= VirtualView.RaiseOnAdImpression;
         _registeredAd.OnAdClicked -= VirtualView.RaiseOnAdClicked;
@@ -178,6 +185,7 @@ private void UnregisterEventHandlers()
         _registeredAd.OnAdClosed -= VirtualView.RaiseOnAdClosed;
 
         _registeredAd = null;
+        _onAdLoaded = null;
         _onAdFailedToLoad = null;
     }