如何从另一个有状态小部件调用有状态小部件中的函数？

Question

Hello I want to call the function that are inside the StatefulWidget of the formCliente class to clean the controllers.but I want to access it via a button that is inside the StatefulWidget of the formFinanceiro class. help me please! thanks.

      class _CadastrarClienteState extends State<CadastrarCliente>
with TickerProviderStateMixin {     
    body: Form(
      key: formkey,
      child: TabBarView(
        physics: physics, //NeverScrollableScrollPhysics()
        controller: _tabController,
        children: [
          FormCliente(),
          FormDocumento(),
          FormVeiculo(),
          FormContrato(),
          FutureBuilder(
              future: getTrabalhaComCota(),
              builder: (context, snapshot) {
                if (snapshot.hasData && !snapshot.hasError) {
                  //   print(' chamada cota:${snapshot.data}');
                  return FormFinanceiro(
                      itemsCota: snapshot.data, formKey: formkey);
                } else {
                  return Center(
                    child: CircularProgressIndicator(),
                  );
                }
              }),
        ],
      ),
    ),

} ]

Answer 1

You can use Streams to achive the same, please see the code below :

import 'package:flutter/material.dart';
import 'dart:async';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        appBar: AppBar(title: Text("Demo")),
        body: MyApps(),
      ),
    );
  }
}

class MyApps extends StatefulWidget {
  @override
  _MyAppsState createState() => _MyAppsState();
}

class _MyAppsState extends State<MyApps> {
  final changeNotifier = new StreamController.broadcast();

  @override
  void dispose() {
    changeNotifier.close();
    super.dispose();
  }

  buttonClicked() => changeNotifier.sink.add(null);

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        FormCliente(
          shouldTriggerChange: changeNotifier.stream,
        ),
        FormFinanceiro(buttonClicked: buttonClicked),
      ],
    );
  }
}

class FormCliente extends StatefulWidget {
  final Stream shouldTriggerChange;

  FormCliente({this.shouldTriggerChange});

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

class _FormClienteState extends State<FormCliente> {
  StreamSubscription streamSubscription;

  @override
  initState() {
    super.initState();
    if (widget.shouldTriggerChange != null) {
      streamSubscription =
          widget.shouldTriggerChange.listen((_) => clearYourFormMethod());
    }
  }

  @override
  didUpdateWidget(FormCliente old) {
    super.didUpdateWidget(old);
    if (widget.shouldTriggerChange != old.shouldTriggerChange) {
      streamSubscription.cancel();
      streamSubscription =
          widget.shouldTriggerChange.listen((_) => clearYourFormMethod());
    }
  }

  @override
  dispose() {
    super.dispose();
    streamSubscription.cancel();
  }

  void clearYourFormMethod() {
    print('Please clear your form here');
  }

  @override
  Widget build(BuildContext context) {
    return Text("FormCliente");
  }
}

class FormFinanceiro extends StatefulWidget {
  final Function buttonClicked;

  FormFinanceiro({this.buttonClicked});

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

class _FormFinanceiroState extends State<FormFinanceiro> {
  @override
  Widget build(BuildContext context) {
    return Column(
      children: <Widget>[
        RaisedButton(
          child: new Text("FormFinanceiro"),
          onPressed: widget.buttonClicked,
        )
      ],
    );
  }
}

Answer 2

You need to lift the state up:

1. Create the controller in _CadastrarClienteState class.
2. Create a callback in _CadastrarClienteState
3. Pass the controller to the child FormFinanceiro .
4. Pass the callback to the child FormCliente .
5. Now, modify your onbuttonpressed function in FormCliente such that the callback is called when the button is pressed.
6. Finally in the callback method present in _CadastrarClienteState , clear the values using controllers.