为什么我的 toast 消息不起作用或在 Flutter 中显示？

Question

I have a scrollable listView full of quotes, now i want to display a toast message whenever the user scrolled to the bottom of the list. Tight now, I use scroll_edge_listener to detect the scrolling position. I tried to use 'if' condition to create a function to display a toast message, but it does not seem to be working. Really appreciate any help. Anyway, this is my code. Still new to Flutter.

import 'package:flutter/material.dart';
import 'quote.dart';
import 'package:scroll_edge_listener/scroll_edge_listener.dart';
import 'package:fluttertoast/fluttertoast.dart';

void main() => runApp(MaterialApp(
  home: QuoteList(),
));

class QuoteList extends StatefulWidget {
@override
_QuoteListState createState() => _QuoteListState();
}

class _QuoteListState extends State<QuoteList> {
final controller = ScrollController(); //For detecting sroll activity
int index = 0;

List<Quote> quotes = [
Quote(author: 'Osca Wilde', text: '1'),
Quote(author: 'Oscar Wilde', text: '2'),
Quote(author: 'Osca Wilde', text: '3'),
Quote(author: 'Oscar Wilde', text: '4'),
Quote(author: 'Osca Wilde', text: '5'),
Quote(author: 'Oscar Wilde', text: '6'),
Quote(author: 'Osca Wilde', text: '7'),
Quote(author: 'Oscar Wilde', text: '8'),
Quote(author: 'Oscar Wilde', text: '6'),
Quote(author: 'Osca Wilde', text: '7'),
Quote(author: 'Oscar Wilde', text: '8'),
];

Widget quoteTemplate(quote) {
return Card(
  margin: EdgeInsets.fromLTRB(16.0, 16.0, 16.0, 0.0),
  child: Padding(
    padding: const EdgeInsets.all(12.0),
    child: Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: <Widget>[
        Text(
          quote.text,
          style: TextStyle(
            fontSize: 18.0,
            color: Colors.grey[800],
          ),
        ),
        SizedBox(height: 6.0),
        Text(
          quote.author,
          style: TextStyle(
            fontSize: 14.0,
            color: Colors.grey[800],
          ),
        )
      ],
    ),
  ),
);
}

var refreshKey = GlobalKey<RefreshIndicatorState>();

@override
void initState() {
super.initState();

controller.addListener(listenScrolling);
}

void listenScrolling() {
if (controller.position.atEdge) {
  final isTop = controller.position.pixels == 0;

  if (isTop) {
    Fluttertoast.showToast(
        msg: "This is top of the list",
        toastLength: Toast.LENGTH_SHORT,
        gravity: ToastGravity.CENTER,
        timeInSecForIosWeb: 1,
        backgroundColor: Colors.red,
        textColor: Colors.white,
        fontSize: 16.0);
   } else {
    Fluttertoast.showToast(
        msg: "This is bottom of the list",
        toastLength: Toast.LENGTH_SHORT,
        gravity: ToastGravity.CENTER,
        timeInSecForIosWeb: 1,
        backgroundColor: Colors.red,
        textColor: Colors.white,
        fontSize: 16.0);
    }
  }
 }

@override
Widget build(BuildContext context) {
return Scaffold(
  backgroundColor: Colors.grey[200],
  appBar: AppBar(
    title: Text('Awesome Quotes'),
    centerTitle: true,
    backgroundColor: Colors.redAccent,
  ),
  body: RefreshIndicator(
    key: refreshKey,
    onRefresh: refreshlist,
    child: ListView(
      children: quotes.map((quote) => quoteTemplate(quote)).toList(),
    ),
  ),
 );
}

Future<void> refreshlist() async {
refreshKey.currentState?.show(atTop: false);
await Future.delayed(Duration(seconds: 1));
quotes.shuffle();
setState(() {});
}
}

My quote.dart model class

class Quote {
String text;
String author;

Quote({required this.text, required this.author});
}

Answer 1

in which scroll do you use your controller? You should use it in your ListView.