title: Android "tools" namespace in layout xml documentation
body: <p>Per the question here,</p>
  
  <p><a href="https://stackoverflow.com/questions/11078487/android-whats-toolscontext-in-layout-files/11110969#11110969">What&#39;s &quot;tools:context&quot; in Android layout files?</a></p>
  
  <p>The 'tools' namespace reference (xmlns:tools="http://schemas.android.com/tools") has begun to appear in my layouts recently, and I want to know more.  The original post only described the 'tools:context' attribute, but I have also noticed usage of the "tools:listitem" attribute appearing when I have designated a preview layout item for a listview, i.e.</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;ListView
      android:id="@+id/lvCustomer"
      tools:listitem="@layout/customer_list_item" &gt;
  &lt;/ListView&gt;
  </code></pre>
  
  <p>Are there more elements?</p>
  
  <p>What brought me to this 'tools' namespace is that I want to be able to have 'preview-only' text (i.e. in a TextView or EditText) when using the layout designer in eclipse.</p>
  
  <p>Currently, I assign the 'text' or 'hint' property for previewing text when arranging my layouts... but then I always have to remember to clear the preview value from within the code.</p>
  
  <p>Ideally, instead of</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;string name="preview_customer_name"&gt;Billy Bob's Roadhouse Pub&lt;/string&gt;
  
  ...
  
  &lt;TextView
      android:id="@+id/tvCustomerName"
      android:text="@string/preview_customer_name"
  &lt;/TextView&gt;
  </code></pre>
  
  <p>have a something like:</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;TextView
      android:id="@+id/tvCustomerName"
      tools:previewText="@string/preview_customer_name"
  &lt;/TextView&gt;
  </code></pre>
  
  <p>Thanks-</p>