// 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/widgets.dart'; import 'package:meta/meta.dart'; import 'theme_data.dart'; export 'theme_data.dart' show Brightness, ThemeData; /// The duration over which theme changes animate. const Duration kThemeAnimationDuration = const Duration(milliseconds: 200); /// Applies a theme to descendant widgets. /// /// See also: /// /// * [AnimatedTheme] /// * [ThemeData] class Theme extends InheritedWidget { /// Applies the given theme [data] to [child]. /// /// The [data] and [child] arguments must not be null. Theme({ Key key, @required this.data, Widget child }) : super(key: key, child: child) { assert(child != null); assert(data != null); } /// Specifies the color and typography values for descendant widgets. final ThemeData data; static final ThemeData _kFallbackTheme = new ThemeData.fallback(); /// The data from the closest instance of this class that encloses the given context. /// /// Defaults to the fallback theme data if none exists. static ThemeData of(BuildContext context) { Theme theme = context.inheritFromWidgetOfExactType(Theme); return theme?.data ?? _kFallbackTheme; } @override bool updateShouldNotify(Theme old) => data != old.data; @override void debugFillDescription(List<String> description) { super.debugFillDescription(description); description.add('$data'); } } /// An animated value that interpolates [ThemeData]s. class ThemeDataTween extends Tween<ThemeData> { /// Creates an interpolation between [begin] and [end]. ThemeDataTween({ ThemeData begin, ThemeData end }) : super(begin: begin, end: end); @override ThemeData lerp(double t) => ThemeData.lerp(begin, end, t); } /// Animated version of [Theme] which automatically transitions the colours, /// etc, over a given duration whenever the given theme changes. /// /// See also: /// /// * [ThemeData] class AnimatedTheme extends ImplicitlyAnimatedWidget { /// Creates an animated theme. /// /// By default, the theme transition uses a linear curve. The [data] and /// [child] arguments must not be null. AnimatedTheme({ Key key, @required this.data, Curve curve: Curves.linear, Duration duration: kThemeAnimationDuration, this.child }) : super(key: key, curve: curve, duration: duration) { assert(child != null); assert(data != null); } /// Specifies the color and typography values for descendant widgets. final ThemeData data; /// The widget below this widget in the tree. final Widget child; @override _AnimatedThemeState createState() => new _AnimatedThemeState(); } class _AnimatedThemeState extends AnimatedWidgetBaseState<AnimatedTheme> { ThemeDataTween _data; @override void forEachTween(TweenVisitor<dynamic> visitor) { // TODO(ianh): Use constructor tear-offs when it becomes possible _data = visitor(_data, config.data, (dynamic value) => new ThemeDataTween(begin: value)); assert(_data != null); } @override Widget build(BuildContext context) { return new Theme( child: config.child, data: _data.evaluate(animation) ); } @override void debugFillDescription(List<String> description) { super.debugFillDescription(description); if (_data != null) description.add('$_data'); } }