i want to know how to get updated data when i used FutureProvider.
How can i get and show updated data again when i click the button?
Does it have good way? or should i give up to use FutureProvider?
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
home: FutureProvider(
create: (_) async => TestDao().findAll(),
child: MyHomePage(title: 'Flutter Demo Home Page')),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
#override
Widget build(BuildContext context) {
var testData = Provider.of<List<String>>(context);
return Scaffold(
floatingActionButton: FloatingActionButton(
onPressed: () {
setState(() {
TestDao().insert('test');
});
},
child: Icon(Icons.add),
),
body: Text('$testData'),
);
}
}
Related
I try to use Polymorphism with the Provider package in Dart/Flutter, but I'm not sure if it is possible or not and if I have made a mistake.
I have two provider class "Provider1" and "Provider2" which extend an abstract class "AbstactProvider", I have a widget "WidgetProvider1Or2"
which need to interact with Provider1 Or Provider2 but flutter throw me a "ProviderNotFoundException".
thanks for yours help!
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:flutter_bloc_concept/cubit/counter_cubit.dart';
import 'package:provider/provider.dart';
abstract class AbstactProvider extends ChangeNotifier {
void printName();
}
class Provider1 extends AbstactProvider {
#override
void printName() {
print("Provider1");
}
}
class Provider2 extends AbstactProvider {
#override
void printName() {
print("Provider2");
}
}
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return BlocProvider(
create: (context) => CounterCubit(),
child: MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: const MyHomePage(title: 'Flutter Demo Home Page'),
),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({Key? key, required this.title}) : super(key: key);
final String title;
#override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
#override
Widget build(BuildContext context) {
Widget widgetProvider1 = ChangeNotifierProvider(
create: (_) => Provider1(),
child: WidgetProvider1(),
);
Widget widgetProvider2 = ChangeNotifierProvider(
create: (_) => Provider2(),
child: WidgetProvider2(),
);
Widget widgetProvider1Or2 = ChangeNotifierProvider(
create: (_) => Provider1(),
child: WidgetProvider1Or2(),
);
return Scaffold(
body: Column(
children: [widgetProvider1, widgetProvider2, widgetProvider1Or2],
),
);
}
}
class WidgetProvider1 extends StatelessWidget {
const WidgetProvider1({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
context.watch<Provider1>();
return Container();
}
}
class WidgetProvider2 extends StatelessWidget {
const WidgetProvider2({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
context.watch<Provider2>();
return Container();
}
}
class WidgetProvider1Or2 extends StatelessWidget {
const WidgetProvider1Or2({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
context.watch<AbstactProvider>();
return Container();
}
}
This question already has answers here:
Flutter calling child class function from parent class
(6 answers)
Closed 7 months ago.
How do I call method of child widget?
class Parent extends StatefulWidget {
const Parent({Key? key}) : super(key: key);
#override
State<Parent> createState() => _ParentState();
}
class _ParentState extends State<Parent> {
#override
Widget build(BuildContext context) {
return Column(
children: [
FloatingActionButton(onPressed: (){
//call child function named funcToCallFromParent
}),
Child(),
],
);
}
}
class Child extends StatefulWidget {
const Child({Key? key}) : super(key: key);
#override
State<Child> createState() => _ChildState();
}
class _ChildState extends State<Child> {
void funcToCallFromParent(){
print('child func called from parent');
}
#override
Widget build(BuildContext context) {
return Container();
}
}
You can use ChangeNotifier to notify the child (or children if you have more than one child that need to be notified) when the parent's button is pressed:
class FloatingActionButtonNotifier extends ChangeNotifier {
void onFloatingActionButtonPressed() => notifyListeners();
}
class Parent extends StatefulWidget {
const Parent({super.key});
#override
State<Parent> createState() => _ParentState();
}
class _ParentState extends State<Parent> {
final FloatingActionButtonNotifier fabNotifier = FloatingActionButtonNotifier();
#override
Widget build(BuildContext context) {
return Column(
children: [
FloatingActionButton(onPressed: fabNotifier.onFloatingActionButtonPressed),
Child(fabNotifier: fabNotifier),
],
);
}
}
class Child extends StatefulWidget {
const Child({
super.key,
required this.fabNotifier,
});
final FloatingActionButtonNotifier fabNotifier;
#override
State<Child> createState() => _ChildState();
}
class _ChildState extends State<Child> {
void funcToCallFromParent() {
print('child func called from parent');
}
#override
void initState() {
super.initState();
widget.fabNotifier.addListener(funcToCallFromParent);
}
#override
void dispose() {
super.dispose();
widget.fabNotifier.removeListener(funcToCallFromParent);
}
#override
Widget build(BuildContext context) {
return Container();
}
}
You can use GlobalKey for Child, and get the state of Child(StatefulWidget). Then call the child's function in the parent widget.
GlobalKey<MyHomePageState> homePageStateKey = GlobalKey<MyHomePageState>();
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
homePageStateKey.currentState?._incrementCounterAfterOneSecond();
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(key: homePageStateKey, title: 'Flutter Demo Home Page'),
);
}
}
You can use a GlobalKey for that.
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
debugShowCheckedModeBanner: false,
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: const MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
final String title;
const MyHomePage({
Key? key,
required this.title,
}) : super(key: key);
#override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
final _key = GlobalKey<_ChildState>();
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(child: Child(key: _key)),
floatingActionButton: FloatingActionButton(
onPressed: () {
// The current state can be null,
// i.e. there is no widget in the tree because it has been unmounted.
_key.currentState?.funcToCallFromParent();
},
tooltip: 'Increment',
child: const Icon(Icons.add),
),
);
}
}
class Child extends StatefulWidget {
const Child({Key? key}) : super(key: key);
#override
State<Child> createState() => _ChildState();
}
class _ChildState extends State<Child> {
void funcToCallFromParent() {
print('child func called from parent');
}
#override
Widget build(BuildContext context) {
return Container();
}
}
See https://api.flutter.dev/flutter/widgets/GlobalKey-class.html
I am having a class instance(SampleData data) as field in the state class of my widget(SecondRoute). The class instance holds in memory while inspecting using the memory profiler. Is that necessary to set null for the instance in dispose() of state class to avoid holding that class object in memory?
import 'package:flutter/material.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: const MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({Key? key, required this.title}) : super(key: key);
final String title;
#override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
late SecondRoute secondRoute;
#override
void initState() {
secondRoute = const SecondRoute();
super.initState();
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: ElevatedButton(
child: const Text('Open route'),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => secondRoute),
);
},
),
));
}
#override
void dispose() {
super.dispose();
}
}
class SecondRoute extends StatefulWidget {
const SecondRoute({Key? key}) : super(key: key);
#override
State<SecondRoute> createState() => _SecondRouteState();
}
class _SecondRouteState extends State<SecondRoute> {
SampleData? data;
#override
void initState() {
data = SampleData('John', 28);
super.initState();
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text("Second Page"),
),
body: Center(
child: Column(children: <Widget>[
Row(
children: [Text(data!.name!), Text(data!.age!.toString())],
),
]),
));
}
#override
void dispose() {
data = null;
super.dispose();
}
}
class SampleData {
SampleData(this.name, this.age);
final String? name;
final double? age;
}
I want to call the method from HomeState class to _MyHomePageState class.But i have no idea to do that.
this is main.dart :
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
#override
Widget build(BuildContext context) {
Home home = new Home();
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: (){}
),
);
}
}
Home class:
class Home extends StatefulWidget {
#override
State<StatefulWidget> createState() {
return HomeState();
}
}
class HomeState extends State<Home> {
int numberPrint(){
setState((){});
}
#override
Widget build(BuildContext context) {
}
}
I want to call the method numberPrint() in floatingbutton in _MyHomePageState class in main.dart.
Please help me to do that.
Please take a look at how I would have handled, this is not the best, but it would give you a better idea.
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
//MyHomePage---------------------------------------------------
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
MyController controller = MyController();
#override
Widget build(BuildContext context) {
Home home = new Home(controller:controller);
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: controller.execute,
),
);
}
}
//Home---------------------------------------------------------------------
class Home extends StatefulWidget {
Home({this.controller});
final MyController controller;
#override
State<StatefulWidget> createState() {
return HomeState();
}
}
class HomeState extends State<Home> {
initState(){
widget.controller.addListener(numberPrint);
}
numberPrint(){
setState((){});
}
#override
Widget build(BuildContext context) {
}
}
//MyController--------------------------------------------------------
class MyController{
Function listener;
addListener(Function fn){
listener = fn;
}
execute(){
listener();
}
}
In general, I use some kind of page nerve center through which widgets can register their setState functions or other things such as FocusNode and even data.
For example,
class PageNerveCenter{
Function requireHomeRebuild;
}
PageNerveCenter _pageNerveCenter = PageNerveCenter();
class Home extends StatefulWidget{...}
class _HomeState extends State<Home>{
...
#override
initState(){
super.initState();
// register setState
_pageNerveCenter.requireHomeRebuild = (){
setState((){})
};
}
#override
dispose(){
// remove setState when object is disposed
_pageNerveCenter.requireHomeRebuild = (){};
}
...
}
In some other widget (same file/library),
_pageNerveCenter.requireHomeRebuild();
This approach then allows you to call a widget's setState from anywhere in the file, from inside another widget.
In my own experience, this approach has helped to easily break down my widget tree and only rebuild those widgets that actually need to rebuilt too.
I would certainly like to hear other more experienced flutter developers about their take on this approach since I am relatively new too.
I am working on a flutter app, and I have some data stored in the state of a widget. In this case it is the string title. I am wondering if I can pass this data through a parent stateless widget and into this stateless widgets parent, which is a stateful widget. If working correctly, I could pass title into the state of MyHomePage and save it into title2. Is there a way to do this or do I have to convert Widget1 into a stateful widget. The only issue with that is that I already wrote the widget, but I am curious. Here is my code. Thanks!
//main.dart
import 'package:flutter/material.dart';
import 'Widget1.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
String title2;
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Hello"),
),
body: Center(
child: Widget1(),
),
);
}
}
/////////////////////////////////////////////
//Widget1.dart
Widget Widget1() {
return Widget2();
}
/////////////////////////////////
//Widget2.dart
import 'package:flutter/material.dart';
class Widget2 extends StatefulWidget {
final String title = "Hello from Widget2";
_Widget2State createState() => _Widget2State();
}
class _Widget2State extends State<Widget2> {
String title = "Hello from Widget2";
#override
Widget build(BuildContext context) {
return Text('${title}');
}
}
Thanks again!
If you are not using any state management except default one then you can pass data between widgets using Navigator. Here is the code example of how to pass String from child Stateless widget (can be stateful too) to its parent widget.
class MyHomePage extends StatefulWidget {
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
String title = "";
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("FIRST WIDGET"),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text("Title from child Stateless widget: $title"),
FlatButton(
onPressed: () => _openSecondWidget(),
child: Text("OPEN SECOND WIDGET"),
)
],
),
),
);
}
void _openSecondWidget() async {
var newTitle = await Navigator.of(context).push(
MaterialPageRoute(
builder: (context) => SecondWidget(),
),
);
setState(() {
title = newTitle;
});
}
}
class SecondWidget extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("SECOND WIDGET"),
),
body: Center(
child: FlatButton(
onPressed: () {
Navigator.of(context).pop("Hi from Second Widget");
},
child: Text("GO BACK"),
),
),
);
}
}
So the button on the first widget is pushing new widget on the screen and awaits for its result. When it gets the result from the second widget I'm using setState updating display of the title variable. And second widget has just one button which removes this widget from the back stack with some parameter which is in this case String, but it can be anything else.
I assume you just want to pass data from StatelessWidget to StatefulWidget and want to access it in its State. Then try this,
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: "Flutter Demo",),
);
}
}
class MyHomePage extends StatefulWidget {
final String title;
const MyHomePage({Key key, this.title}) : super(key: key);
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title), //TODO: use `widget` to access properties
),
body: Center(
child: MyWidget(title: widget.title,),
),
);
}
}
class MyWidget extends StatefulWidget {
final String title;
const MyWidget({Key key, this.title}) : super(key: key);
_MyWidgetState createState() => _MyWidgetState();
}
class _MyWidgetState extends State<MyWidget> {
#override
Widget build(BuildContext context) {
return Text('${widget.title}');
}
}