title: Constraint layout is not visible in android studio
body: <p>My problem I created an app in the android studio, its .xml file (design) is not visible although its text is visible to me, Please provide a solution</p>
  
  <p>Here is how it looks:</p>
  
  <p><img src="https://i.stack.imgur.com/7XmDZ.png" alt="here is how it looks"></p>
  
  <p>my text file(.xml)</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &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"
  tools:context=".MainActivity"&gt;
  
  &lt;TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Hello World!"
      app:layout_constraintBottom_toBottomOf="parent"
      app:layout_constraintLeft_toLeftOf="parent"
      app:layout_constraintRight_toRightOf="parent"
      app:layout_constraintTop_toTopOf="parent"
      app:layout_constraintVertical_bias="0.52" /&gt;
  
  &lt;EditText
      android:id="@+id/editText"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:ems="10"
      android:inputType="numberDecimal"
      tools:ignore="MissingConstraints"
      tools:layout_editor_absoluteX="148dp"
      tools:layout_editor_absoluteY="137dp" /&gt;
  
  &lt;Button
      android:id="@+id/button"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Button"
      tools:ignore="MissingConstraints"
      tools:layout_editor_absoluteX="0dp"
      tools:layout_editor_absoluteY="0dp" /&gt;
  
  &lt;android.support.v7.widget.RecyclerView
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      tools:ignore="MissingConstraints"
      tools:layout_editor_absoluteX="8dp"
      tools:layout_editor_absoluteY="8dp" /&gt;
  
  &lt;TextView
      android:id="@+id/textView"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="TextView"
      tools:ignore="MissingConstraints"
      tools:layout_editor_absoluteX="217dp"
      tools:layout_editor_absoluteY="67dp" /&gt;
  </code></pre>
  
  <p></p>
  
  <p>///Please provide solution for this</p>