Add missing file

app/src/main/java/org/isoron/uhabits/models/ModelObservable.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2016 Álinson Santos Xavier <isoron@gmail.com>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.isoron.uhabits.models;
+
+import java.util.LinkedList;
+import java.util.List;
+
+public class ModelObservable
+{
+    List<Listener> listeners;
+
+    public ModelObservable()
+    {
+        super();
+        listeners = new LinkedList<>();
+    }
+
+    public interface Listener
+    {
+        void onModelChange();
+    }
+
+    public void addListener(Listener l)
+    {
+        listeners.add(l);
+    }
+
+    public void removeListener(Listener l)
+    {
+        listeners.remove(l);
+    }
+
+    void notifyListeners()
+    {
+        for(Listener l : listeners) l.onModelChange();
+    }
+}