I am trying to use load more package-CodePudding

I am trying to use load more package but when I add list and error appears because Topics isn't an int it's a class that contains int and string. I am trying this example, an error appears in list.addAll(List.generate(30, (v) => V));

in the second v: The return type 'int' isn't a 'Topics', as required by the closure's context.

and the Topics is a class here is the code :

class Topics {
  final int id;
  final String title;
  

  Topics({
    required this.id,
    required this.title,
   
  });

  factory Topics.fromJson(Map<String, dynamic> json) {
    return Topics(
      id: json['id'] as int,
      title: json['title'] as String,
    );
  }
}

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

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

class _MyHomePageState extends State<MyHomePage> {
  int get count => list.length;

  List<Topics> list = [];

  void initState() {
    super.initState();
    list.addAll(List.generate(30, (v) => v));
  }

  void load() {
    print("load");
    setState(() {
      list.addAll(List.generate(15, (v) => v));
      print("data count = ${list.length}");
    });
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text(widget.title),
      ),
      body: Container(
        child: RefreshIndicator(
          child: LoadMore(
            isFinish: count >= 60,
            onl oadMore: _loadMore,
            child: ListView.builder(
              itemBuilder: (BuildContext context, int index) {
                return Container(
                  child: Text(list[index].toString()),
                  height: 40.0,
                  alignment: Alignment.center,
                );
              },
              itemCount: count,
            ),
            whenEmptyLoad: false,
            delegate: DefaultLoadMoreDelegate(),
            textBuilder: DefaultLoadMoreTextBuilder.chinese,
          ),
          onRefresh: _refresh,
        ),
      ),
    );
  }

  Future<bool> _loadMore() async {
    print("onLoadMore");
    await Future.delayed(Duration(seconds: 0, milliseconds: 2000));
    load();
    return true;
  }

  Future<void> _refresh() async {
    await Future.delayed(Duration(seconds: 0, milliseconds: 2000));
    list.clear();
    load();
  }
}

Hello, I am trying this example, but nothing is shown on the screen of the emulator, any help??

CodePudding user response：

In both list.addAll(List.generate(30, (v) => v)); do it like this:

list.addAll(List.generate(30, (v) => Topics(id: v, title: 'Title $v')));

CodePudding user response：

The error occurs because you are trying to add int into a list of Topic. This line:

List.generate(30, (v) => v);

generates a list of numbers because you are mapping v (which is an int) to itself. You need to map it to a Topic like this:

list.addAll(List.generate(30, (int v) => Topic(id: v, title: "Topic $v")));

I strongly recommend to use strong typing like above with int v. You could have avoided this error by using strong typing.

CodePudding user response：

In your both initState() and load()do this:

void initState() {
    super.initState();
    list.addAll(List.generate(30, (v) => Topics(id: v, title: '$v')));
  }

  void load() {
    print("load");
    setState(() {
      list.addAll(List.generate(15, (v) => Topics(id: v, title: '$v')));
      print("data count = ${list.length}");
    });
  }

then in your container do this:

Container(
   child: Text(list[index].title),
   height: 40.0,
   alignment: Alignment.center,
)