blob: ba7db38f6dc4aa7ab2324455d0c7a89d01282601 [file] [log] [blame]
// 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 'dart:math' as math;
import 'package:flutter/widgets.dart';
import 'colors.dart';
import 'debug.dart';
import 'icon_button.dart';
import 'icons.dart';
import 'material_localizations.dart';
import 'theme.dart';
/// A widget representing a rotating expand/collapse button. The icon rotates
/// 180 deg when pressed, then reverts the animation on a second press.
/// The underlying icon is [Icons.expand_more].
/// The expand icon does not include a semantic label for accessibility. In
/// order to be accessible it should be combined with a label using
/// [MergeSemantics]. This is done automatically by the [ExpansionPanel] widget.
/// See [IconButton] for a more general implementation of a pressable button
/// with an icon.
class ExpandIcon extends StatefulWidget {
/// Creates an [ExpandIcon] with the given padding, and a callback that is
/// triggered when the icon is pressed.
const ExpandIcon({
Key key,
this.isExpanded = false,
this.size = 24.0,
@required this.onPressed,
this.padding = const EdgeInsets.all(8.0)
}) : assert(isExpanded != null),
assert(size != null),
assert(padding != null),
super(key: key);
/// Whether the icon is in an expanded state.
/// Rebuilding the widget with a different [isExpanded] value will trigger
/// the animation, but will not trigger the [onPressed] callback.
final bool isExpanded;
/// The size of the icon.
/// This property must not be null. It defaults to 24.0.
final double size;
/// The callback triggered when the icon is pressed and the state changes
/// between expanded and collapsed. The value passed to the current state.
/// If this is set to null, the button will be disabled.
final ValueChanged<bool> onPressed;
/// The padding around the icon. The entire padded icon will react to input
/// gestures.
/// This property must not be null. It defaults to 8.0 padding on all sides.
final EdgeInsetsGeometry padding;
_ExpandIconState createState() => new _ExpandIconState();
class _ExpandIconState extends State<ExpandIcon> with SingleTickerProviderStateMixin {
AnimationController _controller;
Animation<double> _iconTurns;
void initState() {
_controller = new AnimationController(duration: kThemeAnimationDuration, vsync: this);
_iconTurns = new Tween<double>(begin: 0.0, end: 0.5).animate(
new CurvedAnimation(
parent: _controller,
curve: Curves.fastOutSlowIn
// If the widget is initially expanded, rotate the icon without animating it.
if (widget.isExpanded) {
_controller.value = math.pi;
void dispose() {
void didUpdateWidget(ExpandIcon oldWidget) {
if (widget.isExpanded != oldWidget.isExpanded) {
if (widget.isExpanded) {
} else {
void _handlePressed() {
if (widget.onPressed != null)
Widget build(BuildContext context) {
final MaterialLocalizations localizations = MaterialLocalizations.of(context);
final String onTapHint = widget.isExpanded ? localizations.expandedIconTapHint : localizations.collapsedIconTapHint;
return new Semantics(
onTapHint: widget.onPressed == null ? null : onTapHint,
child: new IconButton(
padding: widget.padding,
color: Colors.black38,
onPressed: widget.onPressed == null ? null : _handlePressed,
icon: new RotationTransition(
turns: _iconTurns,
child: const Icon(Icons.expand_more)