blob: 2216ef6a10e7a4d5a0fc763368f21d6d8f91425d [file] [log] [blame]
// 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.
import 'arena.dart';
import 'binding.dart';
export 'arena.dart' show GestureArenaEntry, GestureArenaMember;
class _CombiningGestureArenaEntry implements GestureArenaEntry {
_CombiningGestureArenaEntry(this._combiner, this._member);
final _CombiningGestureArenaMember _combiner;
final GestureArenaMember _member;
void resolve(GestureDisposition disposition) {
_combiner._resolve(_member, disposition);
class _CombiningGestureArenaMember extends GestureArenaMember {
_CombiningGestureArenaMember(this._owner, this._pointer);
final GestureArenaTeam _owner;
final List<GestureArenaMember> _members = <GestureArenaMember>[];
final int _pointer;
bool _resolved = false;
GestureArenaMember? _winner;
GestureArenaEntry? _entry;
void acceptGesture(int pointer) {
assert(_pointer == pointer);
assert(_winner != null || _members.isNotEmpty);
_winner ??= _owner.captain ?? _members[0];
for (final GestureArenaMember member in _members) {
if (member != _winner) {
void rejectGesture(int pointer) {
assert(_pointer == pointer);
for (final GestureArenaMember member in _members) {
void _close() {
_resolved = true;
final _CombiningGestureArenaMember? combiner = _owner._combiners.remove(_pointer);
assert(combiner == this);
GestureArenaEntry _add(int pointer, GestureArenaMember member) {
assert(_pointer == pointer);
_entry ??= GestureBinding.instance.gestureArena.add(pointer, this);
return _CombiningGestureArenaEntry(this, member);
void _resolve(GestureArenaMember member, GestureDisposition disposition) {
if (_resolved) {
if (disposition == GestureDisposition.rejected) {
if (_members.isEmpty) {
} else {
assert(disposition == GestureDisposition.accepted);
_winner ??= _owner.captain ?? member;
/// A group of [GestureArenaMember] objects that are competing as a unit in the
/// [GestureArenaManager].
/// Normally, a recognizer competes directly in the [GestureArenaManager] to
/// recognize a sequence of pointer events as a gesture. With a
/// [GestureArenaTeam], recognizers can compete in the arena in a group with
/// other recognizers. Arena teams may have a captain which wins the arena on
/// behalf of its team.
/// When gesture recognizers are in a team together without a captain, then once
/// there are no other competing gestures in the arena, the first gesture to
/// have been added to the team automatically wins, instead of the gestures
/// continuing to compete against each other.
/// When gesture recognizers are in a team with a captain, then once one of the
/// team members claims victory or there are no other competing gestures in the
/// arena, the captain wins the arena, and all other team members lose.
/// For example, [Slider] uses a team without a captain to support both a
/// [HorizontalDragGestureRecognizer] and a [TapGestureRecognizer], but without
/// the drag recognizer having to wait until the user has dragged outside the
/// slop region of the tap gesture before triggering. Since they compete as a
/// team, as soon as any other recognizers are out of the arena, the drag
/// recognizer wins, even if the user has not actually dragged yet. On the other
/// hand, if the tap can win outright, before the other recognizers are taken
/// out of the arena (e.g. if the slider is in a vertical scrolling list and the
/// user places their finger on the touch surface then lifts it, so that neither
/// the horizontal nor vertical drag recognizers can claim victory) the tap
/// recognizer still actually wins, despite being in the team.
/// [AndroidView] uses a team with a captain to decide which gestures are
/// forwarded to the native view. For example if we want to forward taps and
/// vertical scrolls to a native Android view, [TapGestureRecognizer]s and
/// [VerticalDragGestureRecognizer] are added to a team with a captain (the
/// captain is set to be a gesture recognizer that never explicitly claims the
/// gesture).
/// The captain allows [AndroidView] to know when any gestures in the team has
/// been recognized (or all other arena members are out), once the captain wins
/// the gesture is forwarded to the Android view.
/// To assign a gesture recognizer to a team, set
/// [] to an instance of [GestureArenaTeam].
class GestureArenaTeam {
final Map<int, _CombiningGestureArenaMember> _combiners = <int, _CombiningGestureArenaMember>{};
/// A member that wins on behalf of the entire team.
/// If not null, when any one of the [GestureArenaTeam] members claims victory
/// the captain accepts the gesture.
/// If null, the member that claims a victory accepts the gesture.
GestureArenaMember? captain;
/// Adds a new member to the arena on behalf of this team.
/// Used by [GestureRecognizer] subclasses that wish to compete in the arena
/// using this team.
/// To assign a gesture recognizer to a team, see
/// [].
GestureArenaEntry add(int pointer, GestureArenaMember member) {
final _CombiningGestureArenaMember combiner = _combiners.putIfAbsent(
() => _CombiningGestureArenaMember(this, pointer),
return combiner._add(pointer, member);