Questions[flutter]

When compiling my app, this warning appears inside the container. I've been told to use the expanded widget by wrapping the container and it doesn't work.

 return Container(
  width: 500.0,
  height: 600.0,
  margin: const EdgeInsets.symmetric(horizontal: 5.0),
  decoration: BoxDecoration(
    borderRadius: const BorderRadius.all(Radius.circular(8.0)),
    color: color,
    boxShadow: const [
      BoxShadow(
        color: Colors.black,
        blurRadius: 0.0,
        spreadRadius: 0.0,
        offset: Offset(0.0, 0.0), // shadow direction: bottom right
      )
    ],
  ),
  child: Container(
    margin: const EdgeInsets.symmetric(horizontal: 15.0, vertical: 20.0),
    child: Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        Container(
          margin: const EdgeInsets.only(top: 11.0),
          child: Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: [
              Image.asset(
                logo,
                width: 50,
                height: 50,
              ),
              const Icon(Icons.favorite, color: Colors.red),
            ],
          ),
        ),
        const SizedBox(
          height: 10,
        ),
        Text(
          companyname,
          style: const TextStyle(
              fontSize: 12,
              fontWeight: FontWeight.bold,
              color: Colors.white),
        ),
        Text(
          role,
          style: const TextStyle(
              fontSize: 20,
              fontWeight: FontWeight.bold,
              color: Colors.white),
        ),
        Row(
          mainAxisAlignment: MainAxisAlignment.start,
          children: [
            const Icon(
              Icons.location_on,
              color: Colors.white,
              size: 15,
            ),
            Text(
              region,
              style: const TextStyle(
                  fontSize: 12,
                  fontWeight: FontWeight.bold,
                  color: Colors.white),
            ),
          ],
        ),
      ],
    ),
  ),
);

} }

I'm trying to save information from a form to save a new "shopping list" and I get a ProviderNotFoundException error when trying to save. I have made the main page with the list of "shopping lists" and flutter-bloc with cubit and when I press add, it navigates me to another screen where I enter the name of the new list to register it. Should I pass the context to it when navigating? Why doesn't it grab the context if "CreateShopListFormView" is a child widget of HomeView?

In the ShopListsListView I have a BlocBuilder without a BlocProvider that generates and displays the list correctly.

The error it generates is this:

The following ProviderNotFoundException was thrown while handling a gesture:

Error: Could not find the correct Provider above this CreateShopListFormView Widget

HomeView (Main Window)

class HomeView extends StatelessWidget {
  const HomeView({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MultiBlocProvider(
        providers: [
          BlocProvider<ShopListCubit>(create: (_) => ShopListCubit()..init())
        ],
        child: Scaffold(
          appBar: AppBar(
            title: const Text('Shop List'),
          ),
          body: const ShopListsListView(),
          floatingActionButton: FloatingActionButton(
            onPressed: () async {
              Navigator.of(context).push(MaterialPageRoute(
                builder: (context) => CreateShopListFormView(),
              ));
            },
            tooltip: 'Crear Lista de la compra',
            child: const Icon(Icons.add),
          ),
        ));
  }
}

ShopListCubit

class ShopListCubit extends Cubit<List<ShopList>> {
  ShopListCubit() : super([]);

  // final ShopListRepository _shopListRepository;

  void init() {
    //TODO: Call services

    final list = List.generate(
        10, (index) => ShopList(id: index, title: 'Shop list $index'));
    emit(list);
  }

  void createShopList(ShopList shopList) async {
    //TODO: call services
    final list = state;
    shopList.id = state.length + 1;
    list.add(shopList);
    emit(list);
  }
}

ShopList class

class ShopList extends Equatable {
  int id;
  final String title;

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

  @override
  List<Object?> get props => [id];
}

I am making an example to understand how it works and the correct use of InheritedWidget, which until now seems to be misused.

While running the example, reading the documentation, and testing, I notice some issues that I don't understand.

problem 1

Using the example of the documentation on InheritedWidget, they tell us how it works , how to create it and how to use it , all this with an example of Color. But they never tell us how I can change that value of Color.

Example from the documentation :

class FrogColor extends InheritedWidget {
  const FrogColor({
    Key? key,
    required this.color,
    required Widget child,
  }) : super(key: key, child: child);

  final Color color;

  static FrogColor of(BuildContext context) {
    final FrogColor? result = context.dependOnInheritedWidgetOfExactType<FrogColor>();
    assert(result != null, 'No FrogColor found in context');
    return result!;
  }

  @override
  bool updateShouldNotify(FrogColor old) => color != old.color;
}

After some research and looking at several examples, I managed to do the color change by creating a class ColorBlocand using Stream, I use this in my example below when I tackle problem 2

class ColorBloc

class ColorBloc {
  Color myColor;
  ColorBloc({this.myColor = Colors.amber});
  final _color = StreamController<Color>();

  Stream<Color> get colorStream => _color.stream;
  
  void changeColor(Color newColor) {
    _color.add(newColor);
    myColor = newColor;
  }
}

problem 2

When using my own InheritedWidgetI realize that apart from using a listener (such as StreamBuilder) that checks the changes made to the colorBloc.

If you want to use it on a second screen/route, you need to use MaterialAppit otherwise when navigating to it it sends the following error.

════════ Exception caught by widgets library ═══════════════════════════════════
The following NoSuchMethodError was thrown building SecondPage(dirty):
The getter 'colorBloc' was called on null.
Receiver: null
Tried calling: colorBloc

The only way I can get it to work correctly is with MaterialApp, which I don't know if it's the right thing to do since it's not the main of the app and I hope it's a good use of theInheritedWidget

usage exampleInheritedWidget

Home and FirstPage

class MyInheritedWidgetPage extends StatelessWidget {
  final myColor = ColorBloc();
  @override
  Widget build(BuildContext context) {
    myColor.myColor = Colors.blue;
    return MyInheritedWidget(
      colorBloc: myColor,
      child: StreamBuilder<Color>(
          stream: myColor.colorStream,
          builder: (context, snapshot) {
            print('myColor => $myColor');
            return MaterialApp(
              home: FirstPage(),
            );
          }),
    );
  }
}

class FirstPage extends StatelessWidget {
  const FirstPage({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    final color = MyInheritedWidget.of(context).colorBloc;
    return Scaffold(
      appBar: AppBar(
        title: Text('MyInheritedWidget'),
        backgroundColor: color.myColor,
      ),
      body: Center(
        child: Column(
          children: [
            Text('Color nuevo',
                style: TextStyle(
                    color: MyInheritedWidget.of(context).colorBloc.myColor)),
            RaisedButton(
                child: Text('Set color red'),
                onPressed: () {
                  MyInheritedWidget.of(context).colorBloc.changeColor(Colors.red);
                }),
            RaisedButton(
                child: Text('navigate to second page'),
                onPressed: () {
                  Navigator.of(context)
                      .push(MaterialPageRoute(builder: (_) => SecondPage()));
                }),
          ],
        ),
      ),
    );
  }
}

Second Page

class SecondPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final color = MyInheritedWidget.of(context).colorBloc;
    return Scaffold(
      appBar: AppBar(
        title: Text('Second'),
        backgroundColor: color.myColor,
      ),
      body: Center(
        child: Column(
          children: [
            Text('Hola Mundo', style: TextStyle(color: color.myColor),),
            RaisedButton(
                child: Text('Change color to amber'),
                onPressed: () => color.changeColor(Colors.amber))
          ],
        ),
      ),
    );
  }
}

All this is my public repository , which I use for small flutter examples

I want to filter my list by the name of the title since when I look for the title of the item in my list it has to be with the exact name. This is my ListView, when looking for the title of an item it does not look for it as I want. If there is any way to filter by approximation of the title it would be of great help.

import 'package:flutter/material.dart';
import 'package:flutter_application_1/detailsCG.dart';
import 'package:flutter_application_1/model/cantoscglist.dart';

class ListScreenCG extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title:
              Text('Cantos Corario Grande', style: TextStyle(fontSize: 20.0)),
          centerTitle: true,
          actions: <Widget>[
            IconButton(
              onPressed: () {
                showSearch(context: context, delegate: LetraCGSearch());
              },
              icon: Icon(Icons.search),
            )
          ],
        ),
        body: ListView.builder(
            itemCount: cantosListCG.length,
            itemBuilder: (context, index) {
              LetraCG letraCG = cantosListCG[index];
              return Card(
                child: ListTile(
                  title: Text(letraCG.titleCG),
                  //subtitle: Text(letra.numero.toString()),
                  onTap: () {
                    Navigator.push(
                        context,
                        MaterialPageRoute(
                            builder: (context) => DetailsCG(letraCG)));
                  },
                ),
              );
            }));
  }
}

class LetraCGSearch extends SearchDelegate<LetraCG> {
  @override
  List<Widget> buildActions(BuildContext context) {
    return [
      IconButton(
        icon: Icon(Icons.clear),
        onPressed: () {
          query = "";
        },
      )
    ];
  }

  @override
  Widget buildLeading(BuildContext context) {
    return IconButton(
      icon: Icon(Icons.navigate_before),
      onPressed: () {
        Navigator.pop(context);
      },

      /*onPressed: () {
        //close(context, null);
      },
      icon: Icon(Icons.arrow_back),*/
    );
  }

  @override
  Widget buildResults(BuildContext context) {
    return Text(query);
  }

  @override
  Widget buildSuggestions(BuildContext context) {
    final mylist = query.isEmpty
        ? cantosListCG
        : cantosListCG
            .where((element) =>
                element.titleCG.toLowerCase().startsWith(query.toLowerCase()))
            .toList();
    ;
    return mylist.isEmpty
        ? Center(
            child: Text(
            'Not Results Found...',
            style: TextStyle(fontSize: 20),
          ))
        : ListView.builder(
            itemCount: mylist.length,
            itemBuilder: (context, index) {
              final LetraCG letracg = mylist[index];
              return ListTile(
                onTap: () {
                  Navigator.push(
                      context,
                      MaterialPageRoute(
                          builder: (context) => DetailsCG(letracg)));
                },
                title: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: <Widget>[
                    Text(letracg.titleCG),
                    //Text(listitem.letraCG),
                    Divider()
                  ],
                ),
              );
            });
  }
}

This is where I have my list with the items and information I want to filter. I would like to know if there is any way to be able to filter it not by the exact name of the title.

import 'dart:ffi';

import 'package:flutter/material.dart';

class LetraCG {
 int numeroCG;
 String titleCG;
 String letraCG;

 LetraCG({
   required this.numeroCG,
   required this.titleCG,
   required this.letraCG,
 });
}

List<String> cantoslistOnSearch = [];

List<LetraCG> cantosListCG = [
 LetraCG(numeroCG: 1, titleCG: 'No nos rendiremos', letraCG: '''Letra'''),
 LetraCG(numeroCG: 2, titleCG: '2.- Escondido', letraCG: '''Letra'''),
 LetraCG(numeroCG: 4, titleCG: '4.- Humilde', letraCG: '''Letra'''),
 LetraCG(numeroCG: 5, titleCG: 'Tacos', letraCG: ''' Letra '''),
];

Thank you very much for your attention

I need to insert a textformfield at the bottom of my page with a button on the right. On this page and inside the build widget, I have a listview with a fixed size and I want a text to be entered at the end.

@override
Widget build(BuildContext context) {
return new Scaffold(
    appBar: new AppBar(
      title: new Text("Mensajes de trabajo"),
      backgroundColor: Colors.deepOrange,
    ),
    body: Container(
      height: 450,
      child: FutureBuilder(
        future: _capturaComuna(),
        builder: (BuildContext context, AsyncSnapshot snapshot){
          if (snapshot.data == null){
            return Container(
              child: Center(
                child: Text("Cargando...")
              )
            );
          } else {
            return ListView.builder(
              itemCount: snapshot.data.length,
              itemBuilder: (BuildContext context, int index) {
                return Card(
                  child: ListTile(
                    leading: CircleAvatar(
                      backgroundImage: NetworkImage(snapshot.data[index].imagen_mensaje),
                    ),
                    title: new Text(snapshot.data[index].nombre_persona + '   ' + snapshot.data[index].fecha_mensaje),
                    subtitle: Text(snapshot.data[index].texto_mensaje),
                  )
                );
              },
            );
          }
        }
      )
    )
  );
}