388 lines
13 KiB
Dart
388 lines
13 KiB
Dart
// Copyright 2014 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'package:flutter/widgets.dart';
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import 'banner_theme.dart';
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import 'divider.dart';
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import 'material.dart';
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import 'scaffold.dart';
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import 'theme.dart';
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const Duration _materialBannerTransitionDuration = Duration(milliseconds: 250);
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const Curve _materialBannerHeightCurve = Curves.fastOutSlowIn;
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/// Specify how a [MaterialBanner] was closed.
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///
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/// The [ScaffoldMessengerState.showMaterialBanner] function returns a
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/// [ScaffoldFeatureController]. The value of the controller's closed property
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/// is a Future that resolves to a MaterialBannerClosedReason. Applications that need
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/// to know how a [MaterialBanner] was closed can use this value.
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///
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/// Example:
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///
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/// ```dart
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/// ScaffoldMessenger.of(context).showMaterialBanner(
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/// MaterialBanner( ... )
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/// ).closed.then((MaterialBannerClosedReason reason) {
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/// ...
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/// });
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/// ```
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enum MaterialBannerClosedReason {
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/// The material banner was closed through a [SemanticsAction.dismiss].
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dismiss,
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/// The material banner was closed by a user's swipe.
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swipe,
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/// The material banner was closed by the [ScaffoldFeatureController] close callback
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/// or by calling [ScaffoldMessengerState.hideCurrentMaterialBanner] directly.
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hide,
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/// The material banner was closed by a call to [ScaffoldMessengerState.removeCurrentMaterialBanner].
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remove,
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}
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/// A Material Design banner.
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///
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/// A banner displays an important, succinct message, and provides actions for
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/// users to address (or dismiss the banner). A user action is required for it
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/// to be dismissed.
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///
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/// Banners should be displayed at the top of the screen, below a top app bar.
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/// They are persistent and non-modal, allowing the user to either ignore them or
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/// interact with them at any time.
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///
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/// {@tool dartpad}
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/// Banners placed directly into the widget tree are static.
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///
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/// ** See code in examples/api/lib/material/banner/material_banner.0.dart **
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/// {@end-tool}
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///
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/// {@tool dartpad}
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/// MaterialBanner's can also be presented through a [ScaffoldMessenger].
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/// Here is an example where ScaffoldMessengerState.showMaterialBanner() is used to show the MaterialBanner.
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///
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/// ** See code in examples/api/lib/material/banner/material_banner.1.dart **
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/// {@end-tool}
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///
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/// The [actions] will be placed beside the [content] if there is only one.
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/// Otherwise, the [actions] will be placed below the [content]. Use
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/// [forceActionsBelow] to override this behavior.
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///
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/// If the [actions] placed below the [content], they will be laid out in a row.
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/// If there isn't sufficient room to display everything, they are laid out
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/// in a column instead.
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///
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/// The [actions] and [content] must be provided. An optional leading widget
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/// (typically an [Image]) can also be provided. The [contentTextStyle] and
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/// [backgroundColor] can be provided to customize the banner.
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///
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/// This widget is unrelated to the widgets library [Banner] widget.
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class MaterialBanner extends StatefulWidget {
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/// Creates a [MaterialBanner].
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///
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/// The [actions], [content], and [forceActionsBelow] must be non-null.
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/// The [actions].length must be greater than 0. The [elevation] must be null or
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/// non-negative.
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const MaterialBanner({
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super.key,
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required this.content,
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this.contentTextStyle,
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required this.actions,
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this.elevation,
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this.leading,
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this.backgroundColor,
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this.padding,
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this.leadingPadding,
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this.forceActionsBelow = false,
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this.overflowAlignment = OverflowBarAlignment.end,
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this.animation,
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this.onVisible
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}) : assert(elevation == null || elevation >= 0.0),
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assert(content != null),
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assert(actions != null),
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assert(forceActionsBelow != null);
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/// The content of the [MaterialBanner].
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///
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/// Typically a [Text] widget.
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final Widget content;
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/// Style for the text in the [content] of the [MaterialBanner].
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///
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/// If `null`, [MaterialBannerThemeData.contentTextStyle] is used. If that is
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/// also `null`, [TextTheme.bodyText2] of [ThemeData.textTheme] is used.
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final TextStyle? contentTextStyle;
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/// The set of actions that are displayed at the bottom or trailing side of
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/// the [MaterialBanner].
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///
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/// Typically this is a list of [TextButton] widgets.
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final List<Widget> actions;
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/// The z-coordinate at which to place the material banner.
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///
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/// This controls the size of the shadow below the material banner.
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///
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/// Defines the banner's [Material.elevation].
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///
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/// If this property is null, then [MaterialBannerThemeData.elevation] of
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/// [ThemeData.bannerTheme] is used, if that is also null, the default value is 0.
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/// If the elevation is 0, the [Scaffold]'s body will be pushed down by the
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/// MaterialBanner when used with [ScaffoldMessenger].
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final double? elevation;
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/// The (optional) leading widget of the [MaterialBanner].
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///
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/// Typically an [Icon] widget.
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final Widget? leading;
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/// The color of the surface of this [MaterialBanner].
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///
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/// If `null`, [MaterialBannerThemeData.backgroundColor] is used. If that is
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/// also `null`, [ColorScheme.surface] of [ThemeData.colorScheme] is used.
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final Color? backgroundColor;
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/// The amount of space by which to inset the [content].
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///
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/// If the [actions] are below the [content], this defaults to
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/// `EdgeInsetsDirectional.only(start: 16.0, top: 24.0, end: 16.0, bottom: 4.0)`.
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///
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/// If the [actions] are trailing the [content], this defaults to
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/// `EdgeInsetsDirectional.only(start: 16.0, top: 2.0)`.
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final EdgeInsetsGeometry? padding;
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/// The amount of space by which to inset the [leading] widget.
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///
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/// This defaults to `EdgeInsetsDirectional.only(end: 16.0)`.
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final EdgeInsetsGeometry? leadingPadding;
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/// An override to force the [actions] to be below the [content] regardless of
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/// how many there are.
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///
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/// If this is true, the [actions] will be placed below the [content]. If
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/// this is false, the [actions] will be placed on the trailing side of the
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/// [content] if [actions]'s length is 1 and below the [content] if greater
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/// than 1.
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///
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/// Defaults to false.
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final bool forceActionsBelow;
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/// The horizontal alignment of the [actions] when the [actions] laid out in a column.
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///
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/// Defaults to [OverflowBarAlignment.end].
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final OverflowBarAlignment overflowAlignment;
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/// The animation driving the entrance and exit of the material banner when presented by the [ScaffoldMessenger].
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final Animation<double>? animation;
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/// Called the first time that the material banner is visible within a [Scaffold] when presented by the [ScaffoldMessenger].
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final VoidCallback? onVisible;
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// API for ScaffoldMessengerState.showMaterialBanner():
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/// Creates an animation controller useful for driving a [MaterialBanner]'s entrance and exit animation.
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static AnimationController createAnimationController({ required TickerProvider vsync }) {
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return AnimationController(
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duration: _materialBannerTransitionDuration,
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debugLabel: 'MaterialBanner',
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vsync: vsync,
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);
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}
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/// Creates a copy of this material banner but with the animation replaced with the given animation.
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///
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/// If the original material banner lacks a key, the newly created material banner will
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/// use the given fallback key.
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MaterialBanner withAnimation(Animation<double> newAnimation, { Key? fallbackKey }) {
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return MaterialBanner(
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key: key ?? fallbackKey,
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content: content,
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contentTextStyle: contentTextStyle,
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actions: actions,
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elevation: elevation,
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leading: leading,
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backgroundColor: backgroundColor,
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padding: padding,
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leadingPadding: leadingPadding,
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forceActionsBelow: forceActionsBelow,
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overflowAlignment: overflowAlignment,
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animation: newAnimation,
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onVisible: onVisible,
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);
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}
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@override
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State<MaterialBanner> createState() => _MaterialBannerState();
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}
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class _MaterialBannerState extends State<MaterialBanner> {
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bool _wasVisible = false;
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@override
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void initState() {
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super.initState();
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widget.animation?.addStatusListener(_onAnimationStatusChanged);
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}
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@override
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void didUpdateWidget(MaterialBanner oldWidget) {
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super.didUpdateWidget(oldWidget);
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if (widget.animation != oldWidget.animation) {
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oldWidget.animation?.removeStatusListener(_onAnimationStatusChanged);
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widget.animation?.addStatusListener(_onAnimationStatusChanged);
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}
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}
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@override
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void dispose() {
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widget.animation?.removeStatusListener(_onAnimationStatusChanged);
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super.dispose();
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}
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void _onAnimationStatusChanged(AnimationStatus animationStatus) {
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switch (animationStatus) {
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case AnimationStatus.dismissed:
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case AnimationStatus.forward:
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case AnimationStatus.reverse:
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break;
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case AnimationStatus.completed:
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if (widget.onVisible != null && !_wasVisible) {
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widget.onVisible!();
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}
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_wasVisible = true;
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}
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}
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@override
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Widget build(BuildContext context) {
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assert(debugCheckHasMediaQuery(context));
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final MediaQueryData mediaQueryData = MediaQuery.of(context);
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assert(widget.actions.isNotEmpty);
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final ThemeData theme = Theme.of(context);
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final MaterialBannerThemeData bannerTheme = MaterialBannerTheme.of(context);
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final bool isSingleRow = widget.actions.length == 1 && !widget.forceActionsBelow;
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final EdgeInsetsGeometry padding = widget.padding ?? bannerTheme.padding ?? (isSingleRow
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? const EdgeInsetsDirectional.only(start: 16.0, top: 2.0)
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: const EdgeInsetsDirectional.only(start: 16.0, top: 24.0, end: 16.0, bottom: 4.0));
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final EdgeInsetsGeometry leadingPadding = widget.leadingPadding
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?? bannerTheme.leadingPadding
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?? const EdgeInsetsDirectional.only(end: 16.0);
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final Widget buttonBar = Container(
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alignment: AlignmentDirectional.centerEnd,
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constraints: const BoxConstraints(minHeight: 52.0),
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padding: const EdgeInsets.symmetric(horizontal: 8),
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child: OverflowBar(
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overflowAlignment: widget.overflowAlignment,
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spacing: 8,
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children: widget.actions,
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),
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);
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final double elevation = widget.elevation ?? bannerTheme.elevation ?? 0.0;
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final Color backgroundColor = widget.backgroundColor
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?? bannerTheme.backgroundColor
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?? theme.colorScheme.surface;
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final TextStyle? textStyle = widget.contentTextStyle
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?? bannerTheme.contentTextStyle
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?? theme.textTheme.bodyText2;
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Widget materialBanner = Container(
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margin: EdgeInsets.only(bottom: elevation > 0 ? 10.0 : 0.0),
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child: Material(
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elevation: elevation,
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color: backgroundColor,
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child: Column(
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mainAxisSize: MainAxisSize.min,
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children: <Widget>[
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Padding(
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padding: padding,
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child: Row(
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children: <Widget>[
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if (widget.leading != null)
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Padding(
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padding: leadingPadding,
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child: widget.leading,
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),
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Expanded(
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child: DefaultTextStyle(
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style: textStyle!,
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child: widget.content,
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),
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),
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if (isSingleRow)
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buttonBar,
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],
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),
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),
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if (!isSingleRow)
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buttonBar,
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if (elevation == 0)
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const Divider(height: 0),
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],
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),
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),
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);
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// This provides a static banner for backwards compatibility.
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if (widget.animation == null)
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return materialBanner;
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materialBanner = SafeArea(
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child: materialBanner,
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);
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final CurvedAnimation heightAnimation = CurvedAnimation(parent: widget.animation!, curve: _materialBannerHeightCurve);
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final Animation<Offset> slideOutAnimation = Tween<Offset>(
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begin: const Offset(0.0, -1.0),
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end: Offset.zero,
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).animate(CurvedAnimation(
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parent: widget.animation!,
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curve: const Threshold(0.0),
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));
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materialBanner = Semantics(
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container: true,
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liveRegion: true,
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onDismiss: () {
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ScaffoldMessenger.of(context).removeCurrentMaterialBanner(reason: MaterialBannerClosedReason.dismiss);
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},
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child: mediaQueryData.accessibleNavigation
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? materialBanner
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: SlideTransition(
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position: slideOutAnimation,
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child: materialBanner,
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),
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);
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final Widget materialBannerTransition;
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if (mediaQueryData.accessibleNavigation) {
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materialBannerTransition = materialBanner;
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} else {
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materialBannerTransition = AnimatedBuilder(
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animation: heightAnimation,
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builder: (BuildContext context, Widget? child) {
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return Align(
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alignment: AlignmentDirectional.bottomStart,
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heightFactor: heightAnimation.value,
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child: child,
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);
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},
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child: materialBanner,
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);
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}
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return Hero(
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tag: '<MaterialBanner Hero tag - ${widget.content}>',
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child: ClipRect(child: materialBannerTransition),
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);
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}
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}
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