Add main activity.

app/src/main/AndroidManifest.xml

@@ -19,6 +19,18 @@
             android:configChanges="orientation"
             android:screenOrientation="portrait"
             android:theme="@style/AuthenticationTheme">
+            <!--<intent-filter>-->
+                <!--<action android:name="android.intent.action.MAIN" />-->
+
+                <!--<category android:name="android.intent.category.DEFAULT" />-->
+                <!--<category android:name="android.intent.category.LAUNCHER" />-->
+            <!--</intent-filter>-->
+        </activity>
+
+        <activity
+            android:name=".app.MainActivity"
+            android:theme="@style/AppTheme">
+
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
 
@@ -26,6 +38,6 @@
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>
-
     </application>
+
 </manifest>
\ No newline at end of file

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

+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:theme="@style/AuthenticationTheme">
+
+    <FrameLayout
+        android:id="@+id/fragment_container"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent" />
+</LinearLayout>
\ No newline at end of file