Remove remove*handler methods

* User can call set*Handler with null for removing the handler

Author: Jeasmine

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

@@ -621,18 +621,18 @@ static void setRemoteNotificationReceivedHandler(OSRemoteNotificationReceivedHan
          remoteNotificationReceivedHandler = callback;
    }
 
-   public static void setNotificationWillShowInForegroundHandler(NotificationWillShowInForegroundHandler callback) {
+   public static void setNotificationWillShowInForegroundHandler(@Nullable NotificationWillShowInForegroundHandler callback) {
       notificationWillShowInForegroundHandler = callback;
    }
 
-   public static void setNotificationOpenedHandler(OSNotificationOpenedHandler callback) {
+   public static void setNotificationOpenedHandler(@Nullable OSNotificationOpenedHandler callback) {
       notificationOpenedHandler = callback;
 
       if (initDone && notificationOpenedHandler != null)
          fireCallbackForOpenedNotifications();
    }
 
-   public static void setInAppMessageClickHandler(InAppMessageClickHandler callback) {
+   public static void setInAppMessageClickHandler(@Nullable InAppMessageClickHandler callback) {
       inAppMessageClickHandler = callback;
    }
 
@@ -2740,14 +2740,6 @@ public void run() {
          runCancelGroupedNotifications.run();
    }
 
-   public static void removeNotificationWillShowInForegroundHandler() {
-      OneSignal.notificationWillShowInForegroundHandler = null;
-   }
-
-   public static void removeNotificationOpenedHandler() {
-      notificationOpenedHandler = null;
-   }
-
    /**
     * The {@link OSPermissionObserver#onOSPermissionChanged(OSPermissionStateChanges)}
     * method will be fired on the passed-in object when a notification permission setting changes.

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

@@ -1052,7 +1052,7 @@ public void shouldCorrectlyRemoveOpenedHandlerAndFireMissedOnesWhenAddedBack() t
       OneSignal.setNotificationOpenedHandler(getNotificationOpenedHandler());
       threadAndTaskWait();
 
-      OneSignal.removeNotificationOpenedHandler();
+      OneSignal.setNotificationOpenedHandler(null);
       OneSignal_handleNotificationOpen(blankActivity, new JSONArray("[{ \"alert\": \"Robo test message\", \"custom\": { \"i\": \"UUID\" } }]"), false, ONESIGNAL_NOTIFICATION_ID);
       assertNull(lastNotificationOpenedBody);
 
@@ -2739,8 +2739,8 @@ public void onSuccess(JSONObject response) {}
          @Override
          public void onFailure(JSONObject response) {}
       });
-      OneSignal.removeNotificationOpenedHandler();
-      OneSignal.removeNotificationWillShowInForegroundHandler();
+      OneSignal.setNotificationOpenedHandler(null);
+      OneSignal.setNotificationWillShowInForegroundHandler(null);
       threadAndTaskWait();
 
       // Permission subscription wont return until OneSignal init is done
@@ -2771,8 +2771,8 @@ public void onSuccess(JSONObject response) {}
          @Override
          public void onFailure(JSONObject response) {}
       });
-      OneSignal.removeNotificationOpenedHandler();
-      OneSignal.removeNotificationWillShowInForegroundHandler();
+      OneSignal.setNotificationOpenedHandler(null);
+      OneSignal.setNotificationWillShowInForegroundHandler(null);
       threadAndTaskWait();
 
       // TODO change to assertNull(OneSignal.getPermissionSubscriptionState()); when privacy consent public set is removed
@@ -2801,8 +2801,8 @@ public void onSuccess(JSONObject response) {}
          @Override
          public void onFailure(JSONObject response) {}
       });
-      OneSignal.removeNotificationOpenedHandler();
-      OneSignal.removeNotificationWillShowInForegroundHandler();
+      OneSignal.setNotificationOpenedHandler(null);
+      OneSignal.setNotificationWillShowInForegroundHandler(null);
       threadAndTaskWait();
 
       assertNull(OneSignal.getPermissionSubscriptionState());
@@ -2831,8 +2831,8 @@ public void onSuccess(JSONObject response) {}
          @Override
          public void onFailure(JSONObject response) {}
       });
-      OneSignal.removeNotificationOpenedHandler();
-      OneSignal.removeNotificationWillShowInForegroundHandler();
+      OneSignal.setNotificationOpenedHandler(null);
+      OneSignal.setNotificationWillShowInForegroundHandler(null);
       threadAndTaskWait();
 
       assertNull(OneSignal.getPermissionSubscriptionState());