title: Activity not closing on Back press when theme is Theme.NoDisplay
body: <p>I am setting Activity Theme to <code>Theme.NoDisplay</code> but When it open but on press back button Activity not closing/destroying. It should close/destroy on back press.</p>
  
  <p>Guys help me why this is so and any solution to resolve this.</p>
  
  <pre><code>public class MainActivity extends Activity {
  
      // Tag of the Activity
      private static String TAG = "MainActivity";
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
  
          DatabaseManager.init(this);
  
          NFCIItem mNFCItem = new NFCIItem();
          mNFCItem.setSerialNumber(1);
  
          DatabaseManager.getInstance().addWishList(mNFCItem);
          final List&lt;NFCIItem&gt; wishLists = DatabaseManager.getInstance().getAllNFCSerialNumber();
          Log.v(TAG, wishLists.toString());
  
      }
  
      @Override
      public boolean onCreateOptionsMenu(Menu menu) {
          getMenuInflater().inflate(R.menu.main, menu);
          return true;
      }
  }
  </code></pre>
  
  <p>AndroidManifest.xml</p>
  
  <pre><code>&lt;activity
      android:name="com.example.appdemo.MainActivity"
      android:label="@string/app_name"
      android:theme="@android:style/Theme.NoDisplay" &gt;
      &lt;intent-filter&gt;
          &lt;action android:name="android.intent.action.MAIN" /&gt;
  
          &lt;category android:name="android.intent.category.LAUNCHER" /&gt;
      &lt;/intent-filter&gt;
  &lt;/activity&gt;
  </code></pre>