title: Difference between view with class and tag in Android
body: <p>Is there any difference between</p>
  
  <pre><code>&lt;View class="android.support.v7.widget.Toolbar"&gt;
  </code></pre>
  
  <p>And</p>
  
  <pre><code>&lt;android.support.v7.widget.Toolbar&gt;
  </code></pre>
  
  <p>Is there any difference?</p>
  
  <p>I notice that using <code>&lt;android.support.v7.widget.Toolbar&gt;</code> the preview screen shows warnings.</p>