import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Listview bug?'),
    );
  }
}

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

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

class _MyHomePageState extends State<MyHomePage> {

  List<String> items = List<String>();


  void addItemToList(){
    setState(() {
      items.add("test");
    });
  }

  void addIgnoredItemToList() {
    setState(() {
      items.add("ignored");
    });
  }

  @override
  Widget build(BuildContext context) {

    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
        actions: <Widget>[
          FlatButton(
            child: Text(
              "add item",
            ),
            onPressed: addItemToList,
          ),
          FlatButton(
            child: Text(
              "add ignored item",
            ),
            onPressed: addIgnoredItemToList,
          ),
        ],
      ),
      body: Center(
        child: ListView.builder(
          itemCount: items.length,
          itemBuilder: (context, index) {
            Widget output;

            if (items[index] == "ignored") {
              return output;
            } else {
              output = Text(items[index]);
              return output;
            }
          },
        ),
      ),
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.clear),
        tooltip: 'Reset',
        onPressed: (){
          setState(() {
            items.clear();
          });
        },
      ),
    );
  }
}