title: Need a function that is called after a navigator.pop()
body: <p>Quite a simple question but I can't figure out the answer.</p>
  
  <p>I need a function that works like</p>
  
  <pre><code>  componentDidMount() {
  
    }
  </code></pre>
  
  <p>after a <code>navigator.pop</code>. </p>
  
  <p>Basically just a function that is called when the navigator enters the scene/component that was active before a <code>navigator.push()</code>. And is called when it becomes active again after a <code>navigator.pop()</code>?</p>
  
  <p>Like an <code>onEnter()</code> func that is called every time regardless if it's after <code>navigator.pop()</code> or <code>navigator.push()</code>.</p>