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// Copyright 2020 J-P Nurmi
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//
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// ItemSelectionNotifier is based on Flutter's ChangeNotifier:
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// https://github.com/flutter/flutter/blob/master/packages/flutter/lib/src/foundation/change_notifier.dart
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//
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// Copyright 2014 The Flutter Authors. All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without modification,
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// are permitted provided that the following conditions are met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following
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// disclaimer in the documentation and/or other materials provided
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// with the distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived
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// from this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
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// ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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// ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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import 'dart:collection';
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import 'package:flutter/foundation.dart';
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import 'item_selection_types.dart';
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abstract class ItemSelectionNotifier {
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/// Adds a [listener] callback for selection changes at any index.
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void addListener(ItemSelectionChangeCallback listener) {
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assert(_debugAssertNotDisposed());
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_listeners.add(listener);
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}
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/// Removes a [listener] callback for selection changes at any index.
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void removeListener(ItemSelectionChangeCallback listener) {
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assert(_debugAssertNotDisposed());
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_listeners.remove(listener);
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}
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/// Adds a [listener] callback for selection changes at a specific [index] only.
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void addIndexListener(int index, ItemSelectionChangeCallback listener) {
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assert(_debugAssertNotDisposed());
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if (!_indexListeners.containsKey(index)) {
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_indexListeners[index] = ObserverList<ItemSelectionChangeCallback>();
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}
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_indexListeners[index].add(listener);
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}
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/// Removes a [listener] callback for selection changes at a specific [index] only.
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void removeIndexListener(int index, ItemSelectionChangeCallback listener) {
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assert(_debugAssertNotDisposed());
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if (_indexListeners.containsKey(index)) {
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_indexListeners[index].remove(listener);
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}
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}
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/// Notifies all the registered listeners.
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@protected
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void notifyListeners(int index, bool selected) {
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assert(_debugAssertNotDisposed());
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if (_listeners != null) {
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final allListeners = List<ItemSelectionChangeCallback>.from(
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[..._listeners, ...?_indexListeners[index]]);
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for (final listener in allListeners) {
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try {
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listener(index, selected);
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} catch (exception, stack) {
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FlutterError.reportError(
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FlutterErrorDetails(
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exception: exception,
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stack: stack,
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library: 'item_selector',
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context: ErrorDescription(
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'while dispatching notifications for $runtimeType'),
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informationCollector: () sync* {
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yield DiagnosticsProperty<ItemSelectionNotifier>(
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'The $runtimeType sending notification was',
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this,
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style: DiagnosticsTreeStyle.errorProperty,
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);
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},
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),
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);
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}
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}
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}
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}
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/// Discards the listener callbacks. After this method is called, the notifier
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/// object is no longer in a usable state and should be discarded (calls to
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/// [addListener] and [removeListener] will throw after the object is
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/// disposed).
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///
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/// This method should only be called by the object's owner.
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@mustCallSuper
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void dispose() {
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assert(_debugAssertNotDisposed());
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_indexListeners = null;
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_listeners = null;
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}
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bool _debugAssertNotDisposed() {
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assert(() {
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if (_listeners == null || _indexListeners == null) {
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throw FlutterError('A $runtimeType was used after being disposed.\n'
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'Once you have called dispose() on a $runtimeType, it can no longer be used.');
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}
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return true;
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}());
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return true;
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}
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ObserverList<ItemSelectionChangeCallback> _listeners =
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ObserverList<ItemSelectionChangeCallback>();
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HashMap<int, ObserverList<ItemSelectionChangeCallback>> _indexListeners =
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HashMap<int, ObserverList<ItemSelectionChangeCallback>>();
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}
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jpnurmi