title: How to center the elements in ConstraintLayout
body: <p>I am using <code>ConstraintLayout</code> in my application to make applications layout. I am trying to a create a screen wheren one <code>EditText</code> and <code>Button</code> should be in center and <code>Button</code> should be below of <code>EditText</code> with a marginTop only 16dp.</p>
  
  <p>Here is my layout and screenshot how it is looking right now.</p>
  
  <p>activity_authenticate_content.xml</p>
  
  <pre><code>&lt;android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      xmlns:tools="http://schemas.android.com/tools"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:paddingLeft="16dp"
      android:paddingRight="16dp"
      tools:context="com.icici.iciciappathon.login.AuthenticationActivity"&gt;
  
      &lt;android.support.design.widget.TextInputLayout
          android:id="@+id/client_id_input_layout"
          android:layout_width="0dp"
          android:layout_height="wrap_content"
          app:layout_constraintBottom_toBottomOf="parent"
          app:layout_constraintLeft_toLeftOf="parent"
          app:layout_constraintRight_toRightOf="parent"
          app:layout_constraintTop_toTopOf="parent"&gt;
  
          &lt;android.support.design.widget.TextInputEditText
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:hint="@string/login_client_id"
              android:inputType="textEmailAddress" /&gt;
  
      &lt;/android.support.design.widget.TextInputLayout&gt;
  
      &lt;android.support.v7.widget.AppCompatButton
          android:id="@+id/authenticate"
          android:layout_width="0dp"
          android:layout_height="wrap_content"
          android:layout_marginTop="16dp"
          android:text="@string/login_auth"
          app:layout_constraintBottom_toBottomOf="parent"
          app:layout_constraintLeft_toLeftOf="@id/client_id_input_layout"
          app:layout_constraintRight_toRightOf="@id/client_id_input_layout"
          app:layout_constraintTop_toTopOf="@id/client_id_input_layout" /&gt;
  
  &lt;/android.support.constraint.ConstraintLayout&gt;
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/DXyTI.png" rel="noreferrer"><img src="https://i.stack.imgur.com/DXyTI.png" alt="enter image description here"></a></p>