我做过类似的事情，但是不幸的是我的代码还包含很多其他内容，而且要做起来相对繁琐，所以我不得不将它们分解成一个例子，这比我现在能做的要多。我将解释我所做的一般概念。也许还有更好的方法可以做到这一点。

您想编写一个StatefulWidget，其State也扩展了NavigatorObserver（您可以使用无状态的widget，但我认为不是）。我个人将其放置在树中导航器的上方（即，它在其“
build”功能中构建了导航器），但是您很可能也将其置于“导航器”的旁边。

覆盖NavigatorObserver中的didPush，didRemove，didPop等方法。在其中的每一个中，调用setState并保存动画和其他参数，如下所示：

class NavigationFaderState extends State<NavigationFader> with NavigatorObserver {

  Animation _animation;
  // whatever else you need, maybe starting/finishing opacity or position etc.

  @override
  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
    setState(() {
      _animation = route.animation;
    }
    route.animation.addStatusListener((status) {
      if (status = AnimationStatus.completed) {
        setState(() {
          _animation = null;
        });
      }
    });
  }

  ....
}

在您的构建函数中，您需要根据_animation和animate以及是否可能要设置的其他参数（例如，是否要进行动画处理的标志以及前进或后退的标志）进行检查-
我相信“
pop”动画已从0开始并与推入动画一样升至1，但我可能错了）。然后，您可以将该动画连接到想要设置导航栏动画的位置，可以使用AnimatedBuilder或直接将动画连接起来，等等。如果有关于这一切工作方式的任何特定问题，请发表评论，我将添加一些评论，等等。

希望有帮助=）

编辑：完整的代码示例。作为记录，我不建议这段代码那么好，或者您应该这样做。但这是解决问题的一种方法。在实际应用中使用它之前，值得对其进行测试，并可能添加一些断言以检查状态等。

导入’package：flutter / material.dart’;

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  PushListener listener = new PushListener();

  @override
  Widget build(BuildContext context) {
    return new WidgetsApp(
      locale: new Locale("en"),
      navigatorObservers: [listener],
      builder: (context, child) {
        // this is here rather than outside the WidgetsApp so that it
        // gets access to directionality, text styles, etc
        return new Scaffold(
          body: child,
          bottomNavigationBar:
              new ColorChangingNavigationBar(key: listener.navBarKey),
        );
      },
      onGenerateRoute: (settings) {
        switch (settings.name) {
          case '/':
            return new MaterialPageRoute(
              settings: settings,
              builder: (context) => Column(
                    children: <Widget>[
                      new Text(
                          "I have a green nav bar when you open me and blue when you come back"),
                      new RaisedButton(
                        onPressed: () {
                          Navigator.pushNamed(context, "/red");
                        },
                        child: new Text("Next"),
                      ),
                    ],
                  ),
            );
          case '/red':
            return new MaterialPageRoute(
              settings: settings,
              builder: (context) => Column(
                    children: <Widget>[
                      new Text("I have a red nav bar"),
                      new RaisedButton(
                        onPressed: () {
                          Navigator.pop(context);
                        },
                      )
                    ],
                  ),
            );
        }
      },
      color: Colors.blue,
    );
  }
}

class PushListener extends NavigatorObserver {
  GlobalKey<ColorChangingNavigationBarState> navBarKey = new GlobalKey();

  @override
  void didPop(Route route, Route previousRoute) {
    if (route is ModalRoute && navBarKey.currentState != null) {
      var name = route.settings.name;
      var color = name == "/" ? Colors.red.shade500 : Colors.blue.shade500;
      var animation = new ReverseAnimation(route.animation);
      print("Popping & changing color to: ${name == "/" ? "red" : "blue"}");

      navBarKey.currentState.setAnimating(animation, color);
    }
  }

  @override
  void didPush(Route route, Route previousRoute) {
    if (route is ModalRoute && navBarKey.currentState != null) {
      var name = route.settings.name;
      var color = name == "/" ? Colors.blue.shade500 : Colors.red.shade500;
      print("Pushing & changing color to: ${name == "/" ? "red" : "blue"}");
      var animation = route.animation;
      navBarKey.currentState.setAnimating(animation, color);
    }
  }

  @override
  void didRemove(Route route, Route previousRoute) {
    // probably don't need
  }

  @override
  void didStartUserGesture() {
    // might want to do if gestures are supported with whichever type of
    // route you're using.
  }

  @override
  void didStopUserGesture() {
    // if you implement didStartUserGesture
  }
}

class ColorChangingNavigationBar extends StatefulWidget {
  final Color startColor;

  ColorChangingNavigationBar(
      {Key key, this.startColor = const Color.fromRGBO(0, 255, 0, 1.0)})
      : super(key: key);

  @override
  State<StatefulWidget> createState() => new ColorChangingNavigationBarState();
}

class _ColorAnimationInfo {
  final Animation animation;
  final Tween<Color> colorTween;
  final AnimationStatusListener statusListener;

  _ColorAnimationInfo(this.animation, this.colorTween, this.statusListener);
}

class ColorChangingNavigationBarState
    extends State<ColorChangingNavigationBar> {
  @override
  void initState() {
    _toColor = widget.startColor;
    super.initState();
  }

  Color _toColor;
  _ColorAnimationInfo _colorAnimationInfo;

  void setAnimating(Animation animation, Color to) {
    var fromColor;
    if (_colorAnimationInfo != null) {
      fromColor = _colorAnimationInfo.colorTween
          .lerp(_colorAnimationInfo.animation.value);
      _colorAnimationInfo.animation
          .removeStatusListener(_colorAnimationInfo.statusListener);
    } else {
      fromColor = _toColor;
    }

    var statusListener = (state) {
      if (state == AnimationStatus.completed ||
          state == AnimationStatus.dismissed) {
        setState(() {
          _colorAnimationInfo = null;
        });
      }
    };

    animation.addStatusListener(statusListener);

    setState(() {
      _toColor = to;
      Tween<Color> colorTween = new ColorTween(begin: fromColor, end: to);

      _colorAnimationInfo =
          new _ColorAnimationInfo(animation, colorTween, statusListener);
    });
  }

  @override
  Widget build(BuildContext context) {
    if (_colorAnimationInfo != null) {
      return new AnimatedBuilder(
          animation: _colorAnimationInfo.animation,
          builder: (context, child) {
            return new Container(
              color: _colorAnimationInfo.colorTween
                  .lerp(_colorAnimationInfo.animation.value),
              height: 30.0,
            );
          });
    } else {
      return new Container(
        color: _toColor,
        height: 30.0,
      );
    }
  }

  @override
  void dispose() {
    if (_colorAnimationInfo != null) {
      _colorAnimationInfo.animation.removeStatusListener(_colorAnimationInfo.statusListener);
    }
    _colorAnimationInfo = null;
    super.dispose();
  }
}