166 lines
5.2 KiB
Dart
166 lines
5.2 KiB
Dart
import 'package:flutter/material.dart';
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import 'package:unibo_android/src/rust/api/simple.dart';
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import 'package:unibo_android/src/rust/frb_generated.dart';
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import 'package:flutter/material.dart';
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/// Flutter code sample for [ScrollController] & [ScrollNotification].
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void main() => runApp(const ScrollNotificationDemo());
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class ScrollNotificationDemo extends StatefulWidget {
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const ScrollNotificationDemo({super.key});
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@override
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State<ScrollNotificationDemo> createState() => _ScrollNotificationDemoState();
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}
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class _ScrollNotificationDemoState extends State<ScrollNotificationDemo> {
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ScrollNotification? _lastNotification;
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late final ScrollController _controller;
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bool _useController = true;
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// This method handles the notification from the ScrollController.
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void _handleControllerNotification() {
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print('Notified through the scroll controller.');
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// Access the position directly through the controller for details on the
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// scroll position.
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}
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// This method handles the notification from the NotificationListener.
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bool _handleScrollNotification(ScrollNotification notification) {
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print('Notified through scroll notification.');
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// The position can still be accessed through the scroll controller, but
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// the notification object provides more details about the activity that is
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// occurring.
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if (_lastNotification.runtimeType != notification.runtimeType) {
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setState(() {
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// Call set state to respond to a change in the scroll notification.
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_lastNotification = notification;
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});
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}
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// Returning false allows the notification to continue bubbling up to
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// ancestor listeners. If we wanted the notification to stop bubbling,
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// return true.
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return false;
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}
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@override
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void initState() {
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_controller = ScrollController();
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if (_useController) {
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// When listening to scrolling via the ScrollController, call
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// `addListener` on the controller.
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_controller.addListener(_handleControllerNotification);
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}
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super.initState();
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}
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@override
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Widget build(BuildContext context) {
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// ListView.separated works very similarly to this example with
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// CustomScrollView & SliverList.
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Widget body = CustomScrollView(
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// Provide the scroll controller to the scroll view.
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controller: _controller,
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slivers: <Widget>[
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SliverList.separated(
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itemCount: 50,
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itemBuilder: (_, int index) {
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return Padding(
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padding: const EdgeInsets.symmetric(
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vertical: 8.0,
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horizontal: 20.0,
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),
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child: Text('Item $index'),
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);
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},
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separatorBuilder: (_, __) => const Divider(
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indent: 20,
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endIndent: 20,
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thickness: 2,
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),
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),
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],
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);
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if (!_useController) {
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// If we are not using a ScrollController to listen to scrolling,
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// let's use a NotificationListener. Similar, but with a different
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// handler that provides information on what scrolling is occurring.
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body = NotificationListener<ScrollNotification>(
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onNotification: _handleScrollNotification,
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child: body,
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);
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}
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return MaterialApp(
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theme: ThemeData.from(
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useMaterial3: true,
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colorScheme: ColorScheme.fromSeed(seedColor: Colors.blueGrey),
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),
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home: Scaffold(
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appBar: AppBar(
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title: const Text('Listening to a ScrollPosition'),
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bottom: PreferredSize(
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preferredSize: const Size.fromHeight(70),
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child: Column(
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mainAxisAlignment: MainAxisAlignment.spaceAround,
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children: <Widget>[
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if (!_useController)
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Text('Last notification: ${_lastNotification.runtimeType}'),
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if (!_useController) const SizedBox.square(dimension: 10),
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Row(
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mainAxisAlignment: MainAxisAlignment.center,
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children: <Widget>[
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const Text('with:'),
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Radio<bool>(
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value: true,
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groupValue: _useController,
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onChanged: _handleRadioChange,
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),
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const Text('ScrollController'),
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Radio<bool>(
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value: false,
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groupValue: _useController,
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onChanged: _handleRadioChange,
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),
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const Text('NotificationListener'),
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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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body: body,
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),
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);
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}
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void _handleRadioChange(bool? value) {
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if (value == null) {
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return;
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}
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if (value != _useController) {
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setState(() {
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// Respond to a change in selected radio button, and add/remove the
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// listener to the scroll controller.
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_useController = value;
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if (_useController) {
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_controller.addListener(_handleControllerNotification);
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} else {
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_controller.removeListener(_handleControllerNotification);
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}
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});
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}
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}
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@override
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void dispose() {
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_controller.removeListener(_handleControllerNotification);
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super.dispose();
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}
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}
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