listview_note.dart

import 'dart:async';
import 'package:firebase_database/firebase_database.dart';

import 'package:flutter/material.dart';

import 'package:flutter_crud/model/note.dart';
import 'package:flutter_crud/ui/note_screen.dart';

class ListViewNote extends StatefulWidget {
  @override
  _ListViewNoteState createState() => _ListViewNoteState();
}

final notesReference = FirebaseDatabase.instance.reference().child('notes');

class _ListViewNoteState extends State<ListViewNote> {
  List<Note> items;
  StreamSubscription<Event> _onNoteAddedSubscription;
  StreamSubscription<Event> _onNoteChangedSubscription;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();

    items = new List();

    _onNoteAddedSubscription = notesReference.onChildAdded.listen(_onNoteAdded);
    _onNoteChangedSubscription =
        notesReference.onChildChanged.listen(_onNoteUpdated);
  }

  @override
  void dispose() {
    _onNoteAddedSubscription.cancel();
    _onNoteChangedSubscription.cancel();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Firebase CRUD',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Firebase CRUD'),
//          centerTitle: true,
          backgroundColor: Colors.blue,
        ),
        body: Center(
          child: ListView.builder(
            itemCount: items.length,
            padding: EdgeInsets.all(15.0),
            itemBuilder: (context, position) {
              return Column(
                children: <Widget>[
//                  Divider(height: 5.0),
                  ListTile(
                    title: Text(
                      '${items[position].title}',
                      style: TextStyle(
                        fontSize: 22.0,
                        color: Colors.deepOrangeAccent,
                      ),
                    ),
                    subtitle: Text(
                      '${items[position].description}',
                      style: TextStyle(
                        fontSize: 18.0,
                        fontStyle: FontStyle.italic,
                      ),
                    ),
                    leading: Column(
                      children: <Widget>[
                        Padding(padding: EdgeInsets.all(10.0)),
                        CircleAvatar(
                          backgroundColor: Colors.blueAccent,
                          radius: 15.0,
                          child: Text(
                            '${position + 1}',
                            style: TextStyle(
                              fontSize: 22.0,
                              color: Colors.white,
                            ),
                          ),
                        ),
                        IconButton(
                          icon: Icon(Icons.remove_circle_outline),
                          onPressed: () =>
                              _deleteNote(context, items[position], position),
                        ),
                      ],
                    ),
                    onTap: () => _navigateToNote(context, items[position]),
                  ),
                  Divider(height: 5.0),
                ],
              );
            },
          ),
        ),
        floatingActionButton:
            FloatingActionButton(
                child: Icon(Icons.add),
                onPressed: () => _createNewNote(context),
            ),
      ),
    );
  }

  void _onNoteAdded(Event event) {
    setState(() {
      items.add(new Note.fromSnapshot(event.snapshot));
    });
  }

  void _onNoteUpdated(Event event) {
    var oldNoteValue = items.singleWhere((note) => note.id == event.snapshot.key);
    setState(() {
      items[items.indexOf(oldNoteValue)] = new Note.fromSnapshot(event.snapshot);
    });
  }

  void _deleteNote(BuildContext context, Note note, int position) async {
    await notesReference.child(note.id).remove().then((_){
      setState(() {
        items.removeAt(position);
      });
    });
  }

  void _navigateToNote(BuildContext context, Note note) async {
    await Navigator.push(
        context,
        MaterialPageRoute(builder: (context) => NoteScreen(note)),
    );
  }

  void _createNewNote(BuildContext context) async {
    await Navigator.push(
        context,
        MaterialPageRoute(builder: (context) => NoteScreen(Note(null, '', ''))),
    );
  }
}