87 lines
2.9 KiB
Dart
87 lines
2.9 KiB
Dart
/*
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* Copyright (c) 2024-2025 Fabian Freund.
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*
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* This file is part of WebLibre
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* (see https://weblibre.eu).
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as
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* published by the Free Software Foundation, either version 3 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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import 'dart:async';
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import 'package:flutter/material.dart';
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import 'package:flutter_hooks/flutter_hooks.dart';
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/// A hook that manages visibility state based on scroll direction.
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///
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/// Returns a [ValueNotifier<bool>] that automatically updates based on scroll behavior:
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/// - Hides when scrolling down beyond [hideThreshold]
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/// - Shows when scrolling up beyond [showThreshold] or at the top of the scroll view
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/// - Ignores scroll events during [initializationDelay] to prevent hiding during jumpTo/animateTo
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///
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/// Example:
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/// ```dart
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/// final scrollController = useScrollController();
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/// final isVisible = useScrollVisibility(scrollController);
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///
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/// return AnimatedOpacity(
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/// opacity: isVisible.value ? 1.0 : 0.0,
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/// child: FloatingActionButton(...),
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/// );
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/// ```
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ValueNotifier<bool> useScrollVisibility(
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ScrollController scrollController, {
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double hideThreshold = 5.0,
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double showThreshold = 5.0,
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Duration initializationDelay = const Duration(milliseconds: 1000),
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}) {
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final isVisible = useState(true);
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final lastScrollOffset = useRef(0.0);
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final isInitialized = useRef(false);
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useEffect(() {
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// Start timer to enable scroll listener after initialization delay
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final timer = Timer(initializationDelay, () {
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isInitialized.value = true;
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});
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void scrollListener() {
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// Ignore scroll events until initialization is complete
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if (!isInitialized.value) return;
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final currentOffset = scrollController.offset;
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final difference = currentOffset - lastScrollOffset.value;
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// Hide when scrolling down beyond threshold
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if (difference > hideThreshold && isVisible.value) {
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isVisible.value = false;
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}
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// Show when scrolling up beyond threshold or at top
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else if ((difference < -showThreshold || currentOffset <= 0) &&
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!isVisible.value) {
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isVisible.value = true;
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}
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lastScrollOffset.value = currentOffset;
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}
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scrollController.addListener(scrollListener);
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return () {
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timer.cancel();
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scrollController.removeListener(scrollListener);
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};
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}, [scrollController, hideThreshold, showThreshold, initializationDelay]);
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return isVisible;
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}
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