flutter/packages/flutter/test/widget/page_forward_transitions_test.dart

// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter_test/flutter_test.dart' hide TypeMatcher;
import 'package:flutter/material.dart';

class TestTransition extends AnimatedWidget {
  TestTransition({
    Key key,
    this.childFirstHalf,
    this.childSecondHalf,
    Animation<double> animation
  }) : super(key: key, animation: animation);

  final Widget childFirstHalf;
  final Widget childSecondHalf;

  @override
  Widget build(BuildContext context) {
    final Animation<double> animation = this.animation;
    if (animation.value >= 0.5)
      return childSecondHalf;
    return childFirstHalf;
  }
}

class TestRoute<T> extends PageRoute<T> {
  TestRoute({ this.child, RouteSettings settings}) : super(settings: settings);

  final Widget child;

  @override
  Duration get transitionDuration => const Duration(milliseconds: 150);

  @override
  Color get barrierColor => null;

  @override
  Widget buildPage(BuildContext context, Animation<double> animation, Animation<double> forwardAnimation) {
    return child;
  }
}

void main() {
  final Duration kTwoTenthsOfTheTransitionDuration = const Duration(milliseconds: 30);
  final Duration kFourTenthsOfTheTransitionDuration = const Duration(milliseconds: 60);

  testWidgets('Check onstage/offstage handling around transitions', (WidgetTester tester) async {

    GlobalKey insideKey = new GlobalKey();

    String state() {
      String result = '';
      if (tester.any(find.text('A')))
        result += 'A';
      if (tester.any(find.text('B')))
        result += 'B';
      if (tester.any(find.text('C')))
        result += 'C';
      if (tester.any(find.text('D')))
        result += 'D';
      if (tester.any(find.text('E')))
        result += 'E';
      if (tester.any(find.text('F')))
        result += 'F';
      if (tester.any(find.text('G')))
        result += 'G';
      return result;
    }

    await tester.pumpWidget(
      new MaterialApp(
        onGenerateRoute: (RouteSettings settings) {
          switch (settings.name) {
            case '/':
              return new TestRoute<Null>(
                settings: settings,
                child: new Builder(
                  key: insideKey,
                  builder: (BuildContext context) {
                    PageRoute<Null> route = ModalRoute.of(context);
                    return new Column(
                      children: <Widget>[
                        new TestTransition(
                          childFirstHalf: new Text('A'),
                          childSecondHalf: new Text('B'),
                          animation: route.animation
                        ),
                        new TestTransition(
                          childFirstHalf: new Text('C'),
                          childSecondHalf: new Text('D'),
                          animation: route.forwardAnimation
                        ),
                      ]
                    );
                  }
                )
              );
            case '/2': return new TestRoute<Null>(settings: settings, child: new Text('E'));
            case '/3': return new TestRoute<Null>(settings: settings, child: new Text('F'));
            case '/4': return new TestRoute<Null>(settings: settings, child: new Text('G'));
          }
        }
      )
    );

    NavigatorState navigator = insideKey.currentContext.ancestorStateOfType(const TypeMatcher<NavigatorState>());

    expect(state(), equals('BC')); // transition ->1 is at 1.0

    navigator.pushNamed('/2');
    expect(state(), equals('BC')); // transition 1->2 is not yet built
    await tester.pump();
    expect(state(), equals('BCE')); // transition 1->2 is at 0.0

    await tester.pump(kFourTenthsOfTheTransitionDuration);
    expect(state(), equals('BCE')); // transition 1->2 is at 0.4

    await tester.pump(kFourTenthsOfTheTransitionDuration);
    expect(state(), equals('BDE')); // transition 1->2 is at 0.8

    await tester.pump(kFourTenthsOfTheTransitionDuration);
    expect(state(), equals('E')); // transition 1->2 is at 1.0


    navigator.pop();
    expect(state(), equals('E')); // transition 1<-2 is at 1.0, just reversed
    await tester.pump();
    expect(state(), equals('BDE')); // transition 1<-2 is at 1.0

    await tester.pump(kFourTenthsOfTheTransitionDuration);
    expect(state(), equals('BDE')); // transition 1<-2 is at 0.6

    navigator.pushNamed('/3');
    expect(state(), equals('BDE')); // transition 1<-2 is at 0.6
    await tester.pump();
    expect(state(), equals('BDEF')); // transition 1<-2 is at 0.6, 1->3 is at 0.0

    await tester.pump(kFourTenthsOfTheTransitionDuration);
    expect(state(), equals('BCEF')); // transition 1<-2 is at 0.2, 1->3 is at 0.4

    await tester.pump(kFourTenthsOfTheTransitionDuration);
    expect(state(), equals('BDF')); // transition 1<-2 is done, 1->3 is at 0.8

    navigator.pop();
    expect(state(), equals('BDF')); // transition 1<-3 is at 0.8, just reversed
    await tester.pump();
    expect(state(), equals('BDF')); // transition 1<-3 is at 0.8

    await tester.pump(kTwoTenthsOfTheTransitionDuration); // notice that dT=0.2 here, not 0.4
    expect(state(), equals('BDF')); // transition 1<-3 is at 0.6

    await tester.pump(kFourTenthsOfTheTransitionDuration);
    expect(state(), equals('BCF')); // transition 1<-3 is at 0.2

    navigator.pushNamed('/4');
    expect(state(), equals('BCF')); // transition 1<-3 is at 0.2, 1->4 is not yet built
    await tester.pump();
    expect(state(), equals('BCFG')); // transition 1<-3 is at 0.2, 1->4 is at 0.0

    await tester.pump(kFourTenthsOfTheTransitionDuration);
    expect(state(), equals('BCG')); // transition 1<-3 is done, 1->4 is at 0.4

    await tester.pump(kFourTenthsOfTheTransitionDuration);
    expect(state(), equals('BDG')); // transition 1->4 is at 0.8

    await tester.pump(kFourTenthsOfTheTransitionDuration);
    expect(state(), equals('G')); // transition 1->4 is done

  });
}