Merge pull request #1525 from OneSignal/fix/remove_observer_weak_ref_handling

Fix removeObserver WeakReference Handling

Author: jkasten2

OneSignalSDK/onesignal/src/main/java/com/onesignal/OSObservable.java

@@ -55,6 +55,7 @@ void addObserverStrong(ObserverType observer){
    void removeObserver(ObserverType observer) {
       for(int i = 0; i < observers.size(); i++) {
          Object anObserver = ((WeakReference)observers.get(i)).get();
+         if (anObserver == null) continue;
          if (anObserver.equals(observer)) {
             observers.remove(i);
             break;

OneSignalSDK/unittest/src/test/java/com/onesignal/OneSignalPackagePrivateHelper.java

@@ -824,4 +824,18 @@ public OSNotification build() {
          }
       }
    }
+
+   public static class OSObservable<ObserverType, StateType> extends com.onesignal.OSObservable<ObserverType, StateType> {
+      public OSObservable(String methodName, boolean fireOnMainThread) {
+         super(methodName, fireOnMainThread);
+      }
+
+      public void addObserver(ObserverType observer) {
+         super.addObserver(observer);
+      }
+
+      public void removeObserver(ObserverType observer) {
+         super.removeObserver(observer);
+      }
+   }
 }

OneSignalSDK/unittest/src/test/java/com/test/onesignal/MainOneSignalClassRunner.java

@@ -113,6 +113,7 @@
 import org.robolectric.shadows.ShadowConnectivityManager;
 import org.robolectric.shadows.ShadowLog;
 
+import java.lang.ref.WeakReference;
 import java.lang.reflect.Field;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -136,6 +137,7 @@
 import static com.onesignal.OneSignalPackagePrivateHelper.OneSignal_setTime;
 import static com.onesignal.OneSignalPackagePrivateHelper.OneSignal_setTrackerFactory;
 import static com.onesignal.OneSignalPackagePrivateHelper.OneSignal_taskQueueWaitingForInit;
+import static com.onesignal.OneSignalPackagePrivateHelper.OSObservable;
 import static com.onesignal.ShadowOneSignalRestClient.EMAIL_USER_ID;
 import static com.onesignal.ShadowOneSignalRestClient.PUSH_USER_ID;
 import static com.onesignal.ShadowOneSignalRestClient.REST_METHOD;
@@ -3455,6 +3457,15 @@ public void shouldNotFireSMSSubscriptionObserverOnAppRestart() throws Exception
       assertNull(lastSMSSubscriptionStateChanges);
    }
 
+   @Test
+   public void shouldNotThrowWhenRemovingWeakReferenceObservableThatHasBeenGarbageCollected() {
+      OSObservable<Object, Object> observer = new OSObservable<>("", false);
+      WeakReference<Object> weakObject = new WeakReference<>(new Object());
+      observer.addObserver(weakObject.get());
+      Runtime.getRuntime().gc(); // Force cleaning up WeakReference above
+      observer.removeObserver(weakObject.get());
+   }
+
    @Test
    public void shouldGetCorrectCurrentEmailSubscriptionState() throws Exception {
       OneSignalInit();