title: error inflating ConstraintLayout in android studio
body: <p>I'm having problems with Android Studio. I recently upgraded my SDK Manager to include;</p>
  
  <pre><code>compile 'com.android.support.constraint:constraint-layout:1.0.0-beta5'
  </code></pre>
  
  <p>classpath is</p>
  
  <pre><code> classpath 'com.android.tools.build:gradle:2.2.3'
  </code></pre>
  
  <p>Project builds fine. Intellisense and documentation works fine. But when I try to run (in debug) the app on my phone I get this error;</p>
  
  <pre><code> Caused by: android.view.InflateException: Binary XML file line #2:
   Binary XML file line #2: Error inflating class ConstraintLayout
                     at android.view.LayoutInflater.inflate(LayoutInflater.java:539)
                     at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
                     at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
                     at com.android.internal.policy.PhoneWindow.setContentView(PhoneWindow.java:443)
                     at android.app.Activity.setContentView(Activity.java:2172)
  </code></pre>
  
  <p>I've synced gradle. I've restarted Android Studio. I've cleaned and rebuilt the project. </p>
  
  <p>Any ideas on how to fix this?
  thanks!</p>
  
  <p>-edit-
  XML looks like this;</p>
  
  <pre><code>&lt;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:id="@+id/PLAY_PARENT"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:background="@drawable/greenfelt2"
  android:padding="0dp"&gt;
  </code></pre>