Modal Bottom Sheet with Input Fields fix for Flutter

bottom_sheet.dart

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:meta/meta.dart';


Future<T> showModalBottomSheetApp<T>({
	@required BuildContext context,
	@required WidgetBuilder builder,
}) {
	assert(context != null);
	assert(builder != null);
	return Navigator.push(context, new _ModalBottomSheetRoute<T>(
		builder: builder,
		theme: Theme.of(context, shadowThemeOnly: true),
		barrierLabel: MaterialLocalizations
			.of(context)
			.modalBarrierDismissLabel,
	));
}

class _ModalBottomSheetRoute<T> extends PopupRoute<T> {
	_ModalBottomSheetRoute({
		this.builder,
		this.theme,
		this.barrierLabel,
	});

	final WidgetBuilder builder;
	final ThemeData theme;

	@override
	Duration get transitionDuration => const Duration(milliseconds: 200);

	@override
	bool get barrierDismissible => true;

	@override
	final String barrierLabel;

	@override
	Color get barrierColor => Colors.black12;

	AnimationController _animationController;

	@override
	AnimationController createAnimationController() {
		assert(_animationController == null);
		_animationController = BottomSheet.createAnimationController(navigator.overlay);
		return _animationController;
	}

	@override
	Widget buildPage(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
		// By definition, the bottom sheet is aligned to the bottom of the page
		// and isn't exposed to the top padding of the MediaQuery.
		Widget bottomSheet = new MediaQuery.removePadding(
			context: context,
			removeTop: true,
			child: new _ModalBottomSheet<T>(route: this),
		);
		if (theme != null)
			bottomSheet = new Theme(data: theme, child: bottomSheet);
		return bottomSheet;
	}
}


class _ModalBottomSheet<T> extends StatefulWidget {
	const _ModalBottomSheet({ Key key, this.route }) : super(key: key);

	final _ModalBottomSheetRoute<T> route;

	@override
	_ModalBottomSheetState<T> createState() => new _ModalBottomSheetState<T>();
}

class _ModalBottomSheetState<T> extends State<_ModalBottomSheet<T>> {
	@override
	Widget build(BuildContext context) {
		return new AnimatedBuilder(
			animation: widget.route.animation,
			builder: (BuildContext context, Widget child) {
				return new CustomSingleChildLayout(
					delegate: new _ModalBottomSheetLayout(MediaQuery.of(context), widget.route.animation.value),
					child: new BottomSheet(
						animationController: widget.route._animationController,
						onClosing: () => Navigator.pop(context),
						builder: widget.route.builder
					)
				);
			}
		);
	}
}


class _ModalBottomSheetLayout extends SingleChildLayoutDelegate {
	_ModalBottomSheetLayout(this.data, this.progress);

	final MediaQueryData data;
	final double progress;

	@override
	BoxConstraints getConstraintsForChild(BoxConstraints constraints) {
		return new BoxConstraints(
			minWidth: constraints.maxWidth,
			maxWidth: constraints.maxWidth,
			minHeight: 0.0,
			maxHeight: constraints.maxHeight * 9.0 / 16.0
		);
	}

	@override
	Offset getPositionForChild(Size size, Size childSize) {
		return new Offset(0.0, size.height - data.viewInsets.bottom - childSize.height * progress);
	}

	@override
	bool shouldRelayout(_ModalBottomSheetLayout oldDelegate) {
		return progress != oldDelegate.progress;
	}
}