Add FavouriteStatusRouter to forward the favourite status

app/src/main/java/com/hippo/ehviewer/FavouriteStatusRouter.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2019 Hippo Seven
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.hippo.ehviewer;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class FavouriteStatusRouter {
+
+  private List<Listener> listeners = new ArrayList<>();
+
+  public void modifyFavourites(long gid, int slot) {
+    for (Listener listener : listeners) {
+      listener.onModifyFavourites(gid, slot);
+    }
+  }
+
+  public void addListener(Listener listener) {
+    listeners.add(listener);
+  }
+
+  public void removeListener(Listener listener) {
+    listeners.remove(listener);
+  }
+
+  public interface Listener {
+    void onModifyFavourites(long gid, int slot);
+  }
+}