title: React Navigation: How to update navigation title for parent, when value comes from redux and gets updated in child?
body: <p>I'm using <a href="https://github.com/react-community/react-navigation" rel="noreferrer">react-navigation</a> and have a StackNavigator with a  <strong>ParentScreen</strong> and a <strong>ChildScreen</strong>.</p>
  
  <p>Both screens have the same navigation bar with a dynamic value from redux. Implemented like described in <a href="https://github.com/react-community/react-navigation/issues/313" rel="noreferrer">Issue #313</a></p>
  
  <p>This works as expected. When I'm in DetailScreen and I update the value for the count variable, it also updates the value in the navigation bar.</p>
  
  <p>Problem is, if I go back to the parent scene, there is still the old value in the navigation bar. It doesn't update to the current value in redux store.</p>
  
  <p><strong>Child</strong></p>
  
  <p><img src="https://cloud.githubusercontent.com/assets/1635916/24911196/724641de-1eca-11e7-8a34-448c4b398f4f.png" alt="screen shot 2017-04-11 at 15 20 28"></p>
  
  <p><strong>Parent</strong> (when I go back)</p>
  
  <p><img src="https://cloud.githubusercontent.com/assets/1635916/24911239/97c723d8-1eca-11e7-9737-07d2e5851d6f.png" alt="screen shot 2017-04-11 at 15 21 31"></p>
  
  <p><strong>ChildScreen</strong></p>
  
  <pre><code>class ChildScreen extends Component {
    static navigationOptions = {
      title: ({ state }) =&gt; `Total: ${state.params &amp;&amp; state.params.count ?  state.params.count : ''}`
    };
  
    componentWillReceiveProps(nextProps) {
      if (nextProps.count != this.props.count) {
        this.props.navigation.setParams({ count: nextProps.count });
      }
    }
  
    render() {
      return (
        &lt;View&gt;
          &lt;Button onPress={() =&gt; this.props.increment()} title="Increment" /&gt;
        &lt;/View&gt;
      );
    }
  }
  </code></pre>
  
  <p><strong>ParentScreen</strong></p>
  
  <pre><code>class ParentScreen extends Component {
    static navigationOptions = {
    title: ({ state }) =&gt; `Total: ${state.params &amp;&amp; state.params.count ?    state.params.count : ''}`
    };
  }
  </code></pre>
  
  <p>Any advice?</p>