fix issue realm#close() is called dupplicately

app/src/main/java/chat/rocket/android/activity/MainActivity.java

@@ -123,13 +123,6 @@ public class MainActivity extends AbstractAuthedActivity {
     }
   }
 
-  @Override protected void onResume() {
-    super.onResume();
-    if (sessionObserver != null) {
-      sessionObserver.keepalive();
-    }
-  }
-
   @Override protected void onDestroy() {
     if (sessionObserver != null) {
       sessionObserver.unsub();

app/src/main/java/chat/rocket/android/fragment/server_config/InputHostnameFragment.java

@@ -49,7 +49,6 @@ public class InputHostnameFragment extends AbstractServerConfigFragment {
 
   @Override public void onResume() {
     super.onResume();
-    serverConfigObserver.keepalive();
   }
 
   @Override public void onDestroyView() {

app/src/main/java/chat/rocket/android/service/Registerable.java

@@ -9,11 +9,6 @@ public interface Registerable {
    */
   void register();
 
-  /**
-   * keepalive.
-   */
-  void keepalive();
-
   /**
    * unregister.
    */

app/src/main/java/chat/rocket/android/service/RocketChatService.java

@@ -88,7 +88,7 @@ public class RocketChatService extends Service {
       }
       return null;
     }).onSuccessTask(task -> {
-      connectionRequiredServerConfigObserver.keepalive();
+      connectionRequiredServerConfigObserver.sub();
       return null;
     });
     return START_STICKY;
@@ -133,6 +133,13 @@ public class RocketChatService extends Service {
     }
   }
 
+  @Override public void onDestroy() {
+    if (connectionRequiredServerConfigObserver != null) {
+      connectionRequiredServerConfigObserver.unsub();
+    }
+    super.onDestroy();
+  }
+
   @Nullable
   @Override
   public IBinder onBind(Intent intent) {

app/src/main/java/chat/rocket/android/service/RocketChatWebSocketThread.java

@@ -134,8 +134,6 @@ public class RocketChatWebSocketThread extends HandlerThread {
         }
         return null;
       });
-    } else {
-      new Handler(getLooper()).post(this::keepaliveListeners);
     }
   }
 
@@ -227,17 +225,6 @@ public class RocketChatWebSocketThread extends HandlerThread {
     }
   }
 
-  //@DebugLog
-  private void keepaliveListeners() {
-    if (!listenersRegistered) {
-      return;
-    }
-
-    for (Registerable registerable : listeners) {
-      registerable.keepalive();
-    }
-  }
-
   @DebugLog
   private void unregisterListeners() {
     if (!listenersRegistered) {

app/src/main/java/chat/rocket/android/service/ddp/AbstractDDPDocEventSubscriber.java

@@ -139,10 +139,6 @@ abstract class AbstractDDPDocEventSubscriber implements Registerable {
     }
   }
 
-  @Override public void keepalive() {
-
-  }
-
   @Override public void unregister() {
     if (rxSubscription != null) {
       rxSubscription.unsubscribe();

app/src/main/java/chat/rocket/android/service/observer/AbstractModelObserver.java

@@ -27,10 +27,6 @@ abstract class AbstractModelObserver<T extends RealmObject>
     observer.sub();
   }
 
-  @Override public void keepalive() {
-    observer.keepalive();
-  }
-
   @Override public void unregister() {
     observer.unsub();
   }

realm-helpers/src/main/java/chat/rocket/android/realm_helper/AbstractRealmResultsObserver.java

@@ -4,7 +4,6 @@ import io.realm.Realm;
 import io.realm.RealmChangeListener;
 import io.realm.RealmObject;
 import io.realm.RealmResults;
-import timber.log.Timber;
 
 abstract class AbstractRealmResultsObserver<T extends RealmObject> {
   protected Realm realm;
@@ -31,26 +30,16 @@ abstract class AbstractRealmResultsObserver<T extends RealmObject> {
     results.addChangeListener(listener);
   }
 
-  public void keepalive() {
-    if (realm == null || realm.isClosed() || !results.isValid()) {
-      unsub();
-      sub();
-    }
-  }
-
   public void unsub() {
-    try {
+    if (realm != null) {
       if (results != null) {
         if (results.isValid()) {
           results.removeChangeListener(listener);
         }
         results = null;
       }
-      if (realm != null && !realm.isClosed()) {
       realm.close();
-      }
-    } catch (IllegalStateException exception) {
-      Timber.w(exception, "failed to unsub. ignore.");
+      realm = null;
     }
   }