sliver_fill_remaining.dart

// Copyright 2019 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 'dart:async';
import 'dart:io';

import 'package:diagram_capture/diagram_capture.dart';
import 'package:flutter/material.dart';
import 'package:flutter/scheduler.dart';
import 'package:flutter_test/flutter_test.dart';

import 'diagram_step.dart';
import 'fake_drag_scroll_activity.dart';

const Duration _kScrollUpDuration = Duration(seconds: 1);
const Duration _kScrollPauseDuration = Duration(seconds: 1);
final Duration _kTotalDuration = _kScrollPauseDuration + _kScrollUpDuration + _kScrollPauseDuration;

const double _kCurveAnimationFrameRate = 60.0;

class SliverFillRemainingDiagram extends StatefulWidget implements DiagramMetadata {
  const SliverFillRemainingDiagram();

  @override
  String get name => 'sliver_fill_remaining_fill_overscroll';

  @override
  State<StatefulWidget> createState() => _SliverFillRemainingDiagramState();

}

class _SliverFillRemainingDiagramState extends State<SliverFillRemainingDiagram> with TickerProviderStateMixin<SliverFillRemainingDiagram> {
  _SliverFillRemainingDiagramState();

  final ScrollController _scrollController = ScrollController();

  @override
  void initState() {
    super.initState();
    SchedulerBinding.instance!.scheduleFrameCallback((Duration _) {
      _play();
    });
  }

  @override
  void didUpdateWidget(SliverFillRemainingDiagram oldWidget) {
    super.didUpdateWidget(oldWidget);
    _scrollController.jumpTo(0.0);
    SchedulerBinding.instance!.scheduleFrameCallback((Duration _) {
      _play();
    });
  }

  Future<void> _play() async {
    await Future<void>.delayed(_kScrollPauseDuration);
    await _animate(
      to: 400.0,
      duration: _kScrollUpDuration,
    );
    await Future<void>.delayed(_kScrollPauseDuration);
  }

  Future<void> _animate({required double to, required Duration duration}) {
    final ScrollPositionWithSingleContext position = _scrollController.position as ScrollPositionWithSingleContext;
    final FakeDragScrollActivity activity = FakeDragScrollActivity(
      position,
      from: _scrollController.offset,
      to: to,
      duration: duration,
      curve: Curves.easeIn,
      vsync: this,
    );
    _scrollController.position.beginActivity(activity);
    return activity.done;
  }

  @override
  Widget build(BuildContext context) {
    List<Widget> slivers;

    slivers = <Widget>[
      SliverToBoxAdapter(
        child: Container(
          color: Colors.tealAccent[700],
          height: 150.0,
        ),
      ),
      SliverFillRemaining(
        hasScrollBody: false,
        fillOverscroll: true,
        child: Container(
          color: Colors.teal[100],
          child: Align(
            alignment: Alignment.bottomCenter,
            child: Padding(
              padding: const EdgeInsets.all(16.0),
              child: OutlinedButton(
                onPressed: () {},
                child: const Text('Bottom Pinned Button!'),
              ),
            ),
          ),
        ),
      ),
    ];

    return Container(
      color: Colors.white,
      height: 500.0,
      width: 250.0,
      child: Scaffold(
        appBar: AppBar(title: const Text('SliverFillRemaining')),
        body: CustomScrollView(
          physics: const BouncingScrollPhysics(),
          controller: _scrollController,
          slivers: slivers,
        ),
      ),
    );
  }
}

class SliverFillRemainingDiagramStep extends DiagramStep<SliverFillRemainingDiagram> {
  SliverFillRemainingDiagramStep(DiagramController controller) : super(controller);

  @override
  final String category = 'widgets';

  @override
  Future<List<SliverFillRemainingDiagram>> get diagrams async => <SliverFillRemainingDiagram>[
    const SliverFillRemainingDiagram(),
  ];

  @override
  Future<File> generateDiagram(SliverFillRemainingDiagram diagram) async {
    controller.builder = (BuildContext context) => diagram;
    return await controller.drawAnimatedDiagramToFiles(
      end: _kTotalDuration,
      frameRate: _kCurveAnimationFrameRate,
      name: diagram.name,
      category: category,
    );
  }
}