100 lines
2.3 KiB
Dart
100 lines
2.3 KiB
Dart
import 'package:flutter/material.dart';
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class FloatingNavBar extends StatefulWidget {
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final ScrollController? scrollController;
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final Widget child;
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const FloatingNavBar({
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Key? key,
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required this.scrollController,
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required this.child,
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}) : super(key: key);
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@override
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_FloatingNavBarState createState() => _FloatingNavBarState();
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}
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class _FloatingNavBarState extends State<FloatingNavBar> with SingleTickerProviderStateMixin {
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late AnimationController _controller;
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late Animation<Offset> _offsetAnimation;
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double? _lastOffset;
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double _delta = 0;
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static const double _deltaThreshold = 50;
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@override
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void initState() {
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super.initState();
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_controller = AnimationController(
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duration: const Duration(milliseconds: 200),
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vsync: this,
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);
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_offsetAnimation = Tween<Offset>(
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begin: const Offset(0, 0),
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end: const Offset(0, 1),
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).animate(CurvedAnimation(
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parent: _controller,
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curve: Curves.linear,
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))
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..addListener(() {
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if (mounted) {
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setState(() {});
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}
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});
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_registerWidget(widget);
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}
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@override
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void didUpdateWidget(covariant FloatingNavBar oldWidget) {
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super.didUpdateWidget(oldWidget);
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if (oldWidget.scrollController != widget.scrollController) {
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_unregisterWidget(oldWidget);
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_registerWidget(widget);
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}
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}
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@override
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void dispose() {
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_unregisterWidget(widget);
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super.dispose();
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}
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void _registerWidget(FloatingNavBar widget) {
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_lastOffset = null;
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_delta = 0;
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widget.scrollController?.addListener(_onScrollChange);
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}
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void _unregisterWidget(FloatingNavBar widget) {
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widget.scrollController?.removeListener(_onScrollChange);
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}
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@override
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Widget build(BuildContext context) {
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return SlideTransition(
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position: _offsetAnimation,
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child: widget.child,
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);
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}
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void _onScrollChange() {
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final scrollController = widget.scrollController;
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if (scrollController == null) return;
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final offset = scrollController.offset;
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_delta += offset - (_lastOffset ?? offset);
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_lastOffset = offset;
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if (_delta.abs() > _deltaThreshold) {
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if (_delta > 0) {
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// hide
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_controller.forward();
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} else {
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// show
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_controller.reverse();
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}
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_delta = 0;
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}
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}
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}
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