// Copyright 2014 The Flutter Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. // @dart = 2.8 import 'package:flutter/foundation.dart'; import 'package:flutter/rendering.dart'; import 'package:flutter/widgets.dart'; import 'bottom_app_bar_theme.dart'; import 'elevation_overlay.dart'; import 'material.dart'; import 'scaffold.dart'; import 'theme.dart'; // Examples can assume: // Widget bottomAppBarContents; /// A container that is typically used with [Scaffold.bottomNavigationBar], and /// can have a notch along the top that makes room for an overlapping /// [FloatingActionButton]. /// /// Typically used with a [Scaffold] and a [FloatingActionButton]. /// /// {@tool snippet} /// ```dart /// Scaffold( /// bottomNavigationBar: BottomAppBar( /// color: Colors.white, /// child: bottomAppBarContents, /// ), /// floatingActionButton: FloatingActionButton(onPressed: null), /// ) /// ``` /// {@end-tool} /// /// See also: /// /// * [NotchedShape] which calculates the notch for a notched [BottomAppBar]. /// * [FloatingActionButton] which the [BottomAppBar] makes a notch for. /// * [AppBar] for a toolbar that is shown at the top of the screen. class BottomAppBar extends StatefulWidget { /// Creates a bottom application bar. /// /// The [clipBehavior] argument defaults to [Clip.none] and must not be null. /// Additionally, [elevation] must be non-negative. /// /// If [color], [elevation], or [shape] are null, their [BottomAppBarTheme] values will be used. /// If the corresponding [BottomAppBarTheme] property is null, then the default /// specified in the property's documentation will be used. const BottomAppBar({ Key key, this.color, this.elevation, this.shape, this.clipBehavior = Clip.none, this.notchMargin = 4.0, this.child, }) : assert(elevation == null || elevation >= 0.0), assert(notchMargin != null), assert(clipBehavior != null), super(key: key); /// The widget below this widget in the tree. /// /// {@macro flutter.widgets.child} /// /// Typically this the child will be a [Row], with the first child /// being an [IconButton] with the [Icons.menu] icon. final Widget child; /// The bottom app bar's background color. /// /// If this property is null then [BottomAppBarTheme.color] of /// [ThemeData.bottomAppBarTheme] is used. If that's null then /// [ThemeData.bottomAppBarColor] is used. final Color color; /// The z-coordinate at which to place this bottom app bar relative to its /// parent. /// /// This controls the size of the shadow below the bottom app bar. The /// value is non-negative. /// /// If this property is null then [BottomAppBarTheme.elevation] of /// [ThemeData.bottomAppBarTheme] is used. If that's null, the default value /// is 8. final double elevation; /// The notch that is made for the floating action button. /// /// If this property is null then [BottomAppBarTheme.shape] of /// [ThemeData.bottomAppBarTheme] is used. If that's null then the shape will /// be rectangular with no notch. final NotchedShape shape; /// {@macro flutter.widgets.Clip} /// /// Defaults to [Clip.none], and must not be null. final Clip clipBehavior; /// The margin between the [FloatingActionButton] and the [BottomAppBar]'s /// notch. /// /// Not used if [shape] is null. final double notchMargin; @override State createState() => _BottomAppBarState(); } class _BottomAppBarState extends State<BottomAppBar> { ValueListenable<ScaffoldGeometry> geometryListenable; static const double _defaultElevation = 8.0; @override void didChangeDependencies() { super.didChangeDependencies(); geometryListenable = Scaffold.geometryOf(context); } @override Widget build(BuildContext context) { final BottomAppBarTheme babTheme = BottomAppBarTheme.of(context); final NotchedShape notchedShape = widget.shape ?? babTheme.shape; final CustomClipper<Path> clipper = notchedShape != null ? _BottomAppBarClipper( geometry: geometryListenable, shape: notchedShape, notchMargin: widget.notchMargin, ) : const ShapeBorderClipper(shape: RoundedRectangleBorder()); final double elevation = widget.elevation ?? babTheme.elevation ?? _defaultElevation; final Color color = widget.color ?? babTheme.color ?? Theme.of(context).bottomAppBarColor; final Color effectiveColor = ElevationOverlay.applyOverlay(context, color, elevation); return PhysicalShape( clipper: clipper, elevation: elevation, color: effectiveColor, clipBehavior: widget.clipBehavior, child: Material( type: MaterialType.transparency, child: widget.child == null ? null : SafeArea(child: widget.child), ), ); } } class _BottomAppBarClipper extends CustomClipper<Path> { const _BottomAppBarClipper({ @required this.geometry, @required this.shape, @required this.notchMargin, }) : assert(geometry != null), assert(shape != null), assert(notchMargin != null), super(reclip: geometry); final ValueListenable<ScaffoldGeometry> geometry; final NotchedShape shape; final double notchMargin; @override Path getClip(Size size) { // button is the floating action button's bounding rectangle in the // coordinate system whose origin is at the appBar's top left corner, // or null if there is no floating action button. final Rect button = geometry.value.floatingActionButtonArea?.translate( 0.0, geometry.value.bottomNavigationBarTop * -1.0, ); return shape.getOuterPath(Offset.zero & size, button?.inflate(notchMargin)); } @override bool shouldReclip(_BottomAppBarClipper oldClipper) { return oldClipper.geometry != geometry || oldClipper.shape != shape || oldClipper.notchMargin != notchMargin; } }