Update feed events global cache on changing going/interested

.idea/vcs.xml

-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="VcsDirectoryMappings">
-    <mapping directory="$PROJECT_DIR$" vcs="Git" />
-  </component>
-</project>
\ No newline at end of file

app/src/main/java/app/insti/UpdatableList.java

+package app.insti;
+
+import android.os.Handler;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class UpdatableList<T> extends ArrayList<T> {
+    private List<T> cache = new ArrayList<>();
+
+    public List<T> getCache() {
+        return cache;
+    }
+
+    public void setCache(List<T> mCache) {
+        cache = mCache;
+    }
+
+    /** Update existing or add */
+    public void updateCache(T t) {
+        for (int i = 0; i < cache.size(); i++) {
+            T cachedEvent = cache.get(i);
+            if (cachedEvent.equals(t)) {
+                cache.set(i, t);
+                return;
+            }
+        }
+        cache.add(t);
+    }
+}

app/src/main/java/app/insti/Utils.java

@@ -5,9 +5,11 @@ import android.widget.ImageView;
 import com.squareup.picasso.Callback;
 import com.squareup.picasso.Picasso;
 
-import java.time.Instant;
+import app.insti.api.model.Event;
 
 public final class Utils {
+    public static UpdatableList<Event> eventCache = new UpdatableList<>();
+
     public static final void loadImageWithPlaceholder(final ImageView imageView, final String url) {
         Picasso.get()
             .load(resizeImageUrl(url))

app/src/main/java/app/insti/api/model/Event.java

@@ -7,6 +7,7 @@ import com.google.gson.annotations.SerializedName;
 
 import java.sql.Timestamp;
 import java.util.List;
+import java.util.Objects;
 
 public class Event {
     @NonNull()
@@ -223,4 +224,17 @@ public class Event {
     public void setEventBigImage(boolean eventBigImage) {
         this.eventBigImage = eventBigImage;
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Event event = (Event) o;
+        return Objects.equals(eventID, event.eventID);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(eventID);
+    }
 }

app/src/main/java/app/insti/fragment/EventFragment.java

@@ -40,9 +40,9 @@ import java.util.Date;
 import java.util.List;
 
 import app.insti.Constants;
-import app.insti.Utils;
 import app.insti.R;
 import app.insti.ShareURLMaker;
+import app.insti.Utils;
 import app.insti.activity.MainActivity;
 import app.insti.adapter.BodyAdapter;
 import app.insti.api.RetrofitInterface;
@@ -306,6 +306,9 @@ public class EventFragment extends BackHandledFragment {
 
                             event.setEventUserUes(endStatus);
                             setFollowButtonColors(endStatus);
+
+                            // Update global memory cache
+                            Utils.eventCache.updateCache(event);
                         }
                     }
 

app/src/main/java/app/insti/fragment/FeedFragment.java

@@ -5,8 +5,6 @@ import android.app.Activity;
 import android.os.Bundle;
 import android.support.design.widget.FloatingActionButton;
 import android.support.v4.app.Fragment;
-import android.support.v4.app.FragmentManager;
-import android.support.v4.app.FragmentTransaction;
 import android.support.v4.widget.SwipeRefreshLayout;
 import android.support.v7.widget.LinearLayoutManager;
 import android.support.v7.widget.RecyclerView;
@@ -15,19 +13,16 @@ import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 
-import com.google.gson.Gson;
-
 import java.util.List;
 
 import app.insti.ActivityBuffer;
-import app.insti.Constants;
-import app.insti.interfaces.ItemClickListener;
 import app.insti.R;
+import app.insti.Utils;
 import app.insti.activity.MainActivity;
 import app.insti.adapter.FeedAdapter;
 import app.insti.api.RetrofitInterface;
-import app.insti.api.response.NewsFeedResponse;
 import app.insti.api.model.Event;
+import app.insti.api.response.NewsFeedResponse;
 import retrofit2.Call;
 import retrofit2.Callback;
 import retrofit2.Response;
@@ -42,7 +37,6 @@ public class FeedFragment extends BaseFragment {
     private FloatingActionButton fab;
     LinearLayoutManager mLayoutManager;
     public static int index = -1, top = -1;
-    public static List<Event> eventList = null;
     private FeedAdapter feedAdapter = null;
 
     public FeedFragment() {
@@ -78,10 +72,10 @@ public class FeedFragment extends BaseFragment {
         fab = getView().findViewById(R.id.fab);
 
         // Initialize the feed
-        if (eventList == null) {
+        if (Utils.eventCache.getCache() == null || Utils.eventCache.getCache().size() == 0) {
             updateFeed();
         } else {
-            displayEvents(eventList);
+            displayEvents(Utils.eventCache.getCache());
         }
     }
 
@@ -111,8 +105,8 @@ public class FeedFragment extends BaseFragment {
             @Override
             public void onResponse(Call<NewsFeedResponse> call, Response<NewsFeedResponse> response) {
                 if (response.isSuccessful()) {
-                    eventList = response.body().getEvents();
-                    displayEvents(eventList);
+                    Utils.eventCache.setCache(response.body().getEvents());
+                    displayEvents(Utils.eventCache.getCache());
                 }
                 //Server Error
                 feedSwipeRefreshLayout.setRefreshing(false);