title: FadeIn/FadeOut page transition in flutter
body: <p>I am stack at easy problem whitch i am unable to solve. I want to create easy fadein/out page transition in flutter web, but for some reason the transition only occure as FadeIn. Previous page does not fade out.
  Here is a code:</p>
  <pre><code>PageRoute _getPageRoute(Widget child) {
    return _FadeRoute(child: child);
  }
  
  class _FadeRoute extends PageRouteBuilder {
    final Widget child;
    _FadeRoute({this.child})
        : super(
            pageBuilder: (
              BuildContext context,
              Animation&lt;double&gt; animation,
              Animation&lt;double&gt; secondaryAnimation,
            ) =&gt;
                child,
            transitionsBuilder: (
              BuildContext context,
              Animation&lt;double&gt; animation,
              Animation&lt;double&gt; secondaryAnimation,
              Widget child,
            ) =&gt;
                FadeTransition(
              opacity: animation,
              child: child,
            ),
          );
  }
  </code></pre>
  <p>I have searched for hours but coudn't resolved the issue. If anyone of you have any idea, please, dont hesitate to answer! Thanks in advance!</p>