Use material add icon

app/src/main/res/drawable/ic_add_black_24dp.xml

+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24dp"
+        android:height="24dp"
+        android:viewportWidth="24.0"
+        android:viewportHeight="24.0">
+    <path
+        android:fillColor="#FF000000"
+        android:pathData="M19,13h-6v6h-2v-6H5v-2h6V5h2v6h6v2z"/>
+</vector>

app/src/main/res/layout/fragment_calendar.xml

@@ -70,7 +70,7 @@
         android:layout_alignParentBottom="true"
         android:layout_alignParentRight="true"
         android:layout_margin="16dp"
-        android:src="@android:drawable/ic_input_add"
+        android:src="@drawable/ic_add_black_24dp"
         android:tint="@android:color/black"
         android:visibility="gone" />
 

app/src/main/res/layout/fragment_feed.xml

@@ -24,7 +24,7 @@
         android:layout_alignParentBottom="true"
         android:layout_alignParentRight="true"
         android:layout_margin="16dp"
-        android:src="@android:drawable/ic_input_add"
+        android:src="@drawable/ic_add_black_24dp"
         android:tint="@android:color/black"
         android:visibility="gone" />
 

app/src/main/res/layout/fragment_my_events.xml

@@ -25,7 +25,7 @@
         android:layout_alignParentBottom="true"
         android:layout_alignParentRight="true"
         android:layout_margin="16dp"
-        android:src="@android:drawable/ic_input_add"
+        android:src="@drawable/ic_add_black_24dp"
         android:tint="@android:color/black"
         android:visibility="gone" />
 

app/src/main/res/values/drawables.xml

@@ -5,5 +5,4 @@
     <item name="ic_menu_manage" type="drawable">@android:drawable/ic_menu_manage</item>
     <item name="ic_menu_share" type="drawable">@android:drawable/ic_menu_share</item>
     <item name="ic_menu_send" type="drawable">@android:drawable/ic_menu_send</item>
-    <item name="ic_input_add" type="drawable">@android:drawable/ic_input_add</item>
 </resources>