flutter 滚动监听

ScrollController

ScrollController

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return MyHomePageState();
  }
}

class MyHomePageState extends State<MyHomePage> {
  ScrollController scrollController;
  bool isShowTop = false;

  @override
  void initState() {
    // 初始化ScrollController
    scrollController = ScrollController();

    // 监听滚动
    scrollController.addListener(() {
      var tempShowTop = scrollController.offset >= 1000;
      if (tempShowTop != isShowTop) {
        setState(() {
          isShowTop = tempShowTop;
        });
      }
    });

    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return Scaffold(
      appBar: AppBar(
        title: Text("ListView展示"),
      ),
      body: ListView.builder(
        itemCount: 1000,
        itemExtent: 60,
        controller: scrollController,
        itemBuilder: (BuildContext context, int index) {
          return ListTile(
            title: Text("Item$index"),
          );
        },
      ),
      floatingActionButton: !isShowTop
          ? null
          : FloatingActionButton(
              child: Icon(Icons.arrow_upward),
              onPressed: () {
                scrollController.animateTo(0,
                    duration: Duration(milliseconds: 1000), curve: Curves.ease);
              },
            ),
    );
  }
}