title: Android Studio: Activity preview does not show title bar
body: <p>i know this question has been made before <a href="https://stackoverflow.com/questions/29013003/android-studio-not-showing-title-bar-in-preview">here</a>, but i have tried the solution given and i don't get the preview look in the exact style like the device does.</p>
  
  <p>I am using a Samsung Galaxy S3 mini on android version 4.2.2 as my device debugging, it is completely unmodified but i don't understand why, even when i change the theme, the device still looks the same (with the changes made in the activity of course)</p>
  
  <p>the code of the activity is just like any new blank activity</p>
  
  <pre><code>&lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
      android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
      android:paddingRight="@dimen/activity_horizontal_margin"
      android:paddingTop="@dimen/activity_vertical_margin"
      android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity"&gt;
  
      &lt;TextView android:text="@string/hello_world" android:layout_width="wrap_content"
          android:layout_height="wrap_content" /&gt;
  
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>the preview looks like this
  <img src="https://i.stack.imgur.com/KJFrX.png" alt="enter image description here"></p>
  
  <p>but the device looks like this
  <img src="https://i.stack.imgur.com/l3aaI.png" alt="enter image description here"></p>
  
  <p>PS: I am learning android, so i might get confused with the answer</p>