title: Rebuild/refresh specific widget in PageView different class
body: <p>I have a main screen containing a pageview. The pageview has three children, each being a separate class:</p>
  
  <pre><code>children: &lt;Widget&gt;[
        FirstScreen(),
        SecondScreen(),
        ThirdScreen(),
  </code></pre>
  
  <p>These screens load data from a database and are StatefulWidgets. I add data to that database from a separate screen that I open on my main screen.</p>
  
  <p>I want to trigger the <code>setState</code> method for these three screens after I add the data to the database.</p>
  
  <p>How do I access these screens when they are in a different class?</p>