如何使ScrollListener与FutureBuilder一起使用？

Question

跟随this来检测何时到达列表末尾，但似乎ScrollListener无法正常工作，原因是我调试的打印功能也没有输出

使用该按钮可以成功扩展列表，但我的计划是摆脱该按钮并在到达底部时自动添加

class _AllProjectsState extends State<AllProjects> {

  ScrollController sc;

  void initstate() {
    sc = ScrollController();
    super.initState();
    sc.addListener(scListener);
  }

  scListener() {
    print("Changed");
    if( sc.offset >= sc.position.maxScrollExtent && !sc.position.outOfRange) {
      setState(() {
        print("Reached");
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Project Info'),
      ),
      backgroundColor: Colors.white,
      body:FutureBuilder<Data>(
        future: getData(),
        builder: (context, snapshot) {

          if(snapshot.hasData)
            return ListView.builder(
              controller: sc,
              itemCount: snapshot.data.projects.length,
              itemBuilder: (context,index) {
                return ListTile(
                  title: Text('${snapshot.data.projects[index].attributes.name}',style: TextStyle(fontSize: 30),),
                );
              }
            );
          else
            return Text('NotFound');
        }
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          if(!full) {
            setState(() {
              page+=1;
            }); 
          }
        },
        child: Icon(Icons.add),
      ),
    );
  }
}

Answer 1

您可以在下面复制粘贴运行完整代码
您有错字void initstate()，需要@override

代码段

@override
  void initState() {

工作演示

完整代码

import 'package:flutter/material.dart';

class Attributes {
  String name;

  Attributes({this.name});
}

class Project {
  Attributes attributes;

  Project({this.attributes});
}

class Data {
  List<Project> projects;

  Data({this.projects});
}

class AllProjects extends StatefulWidget {
  @override
  _AllProjectsState createState() => _AllProjectsState();
}

class _AllProjectsState extends State<AllProjects> {
  ScrollController sc;
  Project project = Project(attributes: Attributes(name: "test"));
  List<Project> projectList = [];

  @override
  void initState() {
    projectList.add(project);
    projectList.add(project);
    projectList.add(project);
    projectList.add(project);
    projectList.add(project);
    projectList.add(project);
    projectList.add(project);
    projectList.add(project);
    projectList.add(project);
    projectList.add(project);
    projectList.add(project);
    projectList.add(project);
    sc = ScrollController();
    super.initState();
    sc.addListener(scListener);
  }

  scListener() {
    print("Changed");
    if (sc.offset >= sc.position.maxScrollExtent && !sc.position.outOfRange) {
      setState(() {
        print("Reached");
      });
    }
  }

  Future<Data> getData() {
    Project project = Project(attributes: Attributes(name: "123"));
    projectList.add(project);
    Data data = Data(projects: projectList);
    return Future.value(data);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Project Info'),
      ),
      backgroundColor: Colors.white,
      body: FutureBuilder<Data>(
          future: getData(),
          builder: (context, snapshot) {
            if (snapshot.hasData)
              return ListView.builder(
                  controller: sc,
                  itemCount: snapshot.data.projects.length,
                  itemBuilder: (context, index) {
                    return ListTile(
                      title: Text(
                        '${snapshot.data.projects[index].attributes.name}',
                        style: TextStyle(fontSize: 30),
                      ),
                    );
                  });
            else
              return Text('NotFound');
          }),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          /*if (!full) {
            setState(() {
              page += 1;
            });
          }*/
        },
        child: Icon(Icons.add),
      ),
    );
  }
}

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: AllProjects(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}