使用 onGenerateRoute 的屏幕之间的条件退出转换

Question

我正在通过onGenerateRoute 设置我的路线和过渡动画，这很好用，除了我想要根据条件（例如在选择的路径上）不同的过渡动画：

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      initialRoute: '/',
      onGenerateRoute: (RouteSettings settings) {
        if (settings.name == '/') {
          return PageRouteBuilder<dynamic>(
            pageBuilder: (BuildContext context, Animation<double> animation,
                    Animation<double> secondaryAnimation) =>
                Page1(),
            transitionsBuilder: (
              BuildContext context,
              Animation<double> animation,
              Animation<double> secondaryAnimation,
              Widget child,
            ) {
              return SlideTransition(
                position: Tween<Offset>(
                  begin: Offset.zero,
                  end: const Offset(-1.0, 0.0),
                ).animate(secondaryAnimation), // Here I want to have differents transitions
                child: child,
              );
            },
          );
        } else if (settings.name == '/second') {
          return PageRouteBuilder<dynamic>(
            pageBuilder: (BuildContext context, Animation<double> animation,
                    Animation<double> secondaryAnimation) =>
                Page2(),
            transitionsBuilder: (
              BuildContext context,
              Animation<double> animation,
              Animation<double> secondaryAnimation,
              Widget child,
            ) {
              return SlideTransition(
                  position: Tween<Offset>(
                          begin: const Offset(1.0, 0.0), end: Offset.zero)
                      .animate(animation),
                  child: SlideTransition(
                    position: Tween<Offset>(
                      begin: Offset.zero,
                      end: const Offset(0.0, 1.0),
                    ).animate(secondaryAnimation),
                    child: child,
                  ));
            },
          );
        } else if (settings.name == '/third') {
          return PageRouteBuilder<dynamic>(
            pageBuilder: (BuildContext context, Animation<double> animation,
                    Animation<double> secondaryAnimation) =>
                Page3(),
            transitionsBuilder: (
              BuildContext context,
              Animation<double> animation,
              Animation<double> secondaryAnimation,
              Widget child,
            ) {
              return SlideTransition(
                  position: Tween<Offset>(
                          begin: const Offset(0.0, 1.0), end: Offset.zero)
                      .animate(animation),
                  child: SlideTransition(
                    position: Tween<Offset>(
                      begin: Offset.zero,
                      end: const Offset(0.0, 1.0),
                    ).animate(secondaryAnimation),
                    child: child,
                  ));
            },
          );
        } else {
          return null;
        }
      },
    );
  }
}

class Page1 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("Page 1"), backgroundColor: Colors.blue),
      backgroundColor: Colors.blue,
      body: Column(
        children: [
          Center(
            child: RaisedButton(
              onPressed: () => Navigator.pushNamed(context, '/second'),
              child: Text("Go to Page 2 with exit transition slide left"),
            ),
          ),
          Center(
            child: RaisedButton(
              onPressed: () => Navigator.pushNamed(context, '/third'),
              child: Text("Go to Page 3 with transition slide top"),
            ),
          ),
        ],
      ),
    );
  }
}

class Page2 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("Page 2"), backgroundColor: Colors.green),
      backgroundColor: Colors.green,
      body: Center(
          child: RaisedButton(
              onPressed: () => Navigator.of(context).pop(),
              child: Text("Go back to page 1"))),
    );
  }
}

class Page3 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("Page 3"), backgroundColor: Colors.yellow),
      backgroundColor: Colors.yellow,
      body: Center(
          child: RaisedButton(
              onPressed: () => Navigator.of(context).pop(),
              child: Text("Go back to page 1"))),
    );
  }
}

See codePen here

由于在屏幕显示之前设置了退出过渡动画（通过secondaryAnimation），因此我无法根据单击的按钮动态更改动画。我怎样才能做到这一点？

Answer 1

   (RouteSettings settings) {
      final transition = settings.arguments as String;
      if (settings.name == '/') {
      return PageRouteBuilder<dynamic>(
        pageBuilder: (BuildContext context, Animation<double> animation,
                Animation<double> secondaryAnimation) =>
            Page1(),
        transitionsBuilder: (
          BuildContext context,
          Animation<double> animation,
          Animation<double> secondaryAnimation,
          Widget child,
        ) {
           switch (transition) {
             case 'firstTransition':
               secondaryAnimation = //first animation 
             break;
             case 'secondTransition':
               secondaryAnimation = //second animation
             break;
           }

          return SlideTransition(
            position: Tween<Offset>(
              begin: Offset.zero,
              end: const Offset(-1.0, 0.0),
            ).animate(secondaryAnimation), // Here I want to have differents transitions
            child: child,
          );
        },
      );