title: What is the meaning of xmlns:tools in Android XML layout?
body: <p>For example, in:</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" &gt;
  ...
  </code></pre>
  
  <p>Do I need to put it?</p>