Add APPLICATION_ID to project's AndroidManifest.xml file

Author: David Lin

app/src/main/AndroidManifest.xml

@@ -21,6 +21,10 @@
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>
+
+        <meta-data
+            android:name="com.google.android.gms.ads.APPLICATION_ID"
+            android:value="ca-app-pub-0000000000000000~0000000000"/>
     </application>
 
 </manifest>