The value does not come from the alert window - Flutter

rozerro
April 21, 2023
167 views
0 votes
2 Answers

When the onConfirmBtnTap button is pressed in the alert, control is transferred to the previous screen, where this value is displayed in the navigation processing function. However, null comes.

Why doesn’t the value come from alert? (it’s in onTapFunction)

// start
class FirstPage extends StatefulWidget {...}
class _FirstPageState extends State<FirstPage> {

  @override
  Widget build(BuildContext context) {
    debugPrint('-------------building outer----------'); //true
    return Scaffold(
      body: Column(
        children: [
          ...
          InnerWidget(key: UniqueKey()), //unique
        ],
      ),
    );
  }
}
    
// Inner widget
class InnerWidget extends StatefulWidget {...}
class _InnerWidgetState extends State<InnerWidget> {
  ...
  @override
  Widget build(BuildContext context) {
    debugPrint('building inner widget...');
    ...
    // in gesture detector
    onTap: () {
        var productData = ...;
        onTapFunction(context, Group(productData));
    },
  }

  // onTapFunction is defined in InnerWidget
  onTapFunction(BuildContext context, Widget route) async {
    final reLoadPage = await Navigator.push(
      context,
      MaterialPageRoute(
        builder: (context) => route,
      ),
    );
    if (reLoadPage ?? false) { // the value of reloadPage is null
      debugPrint('---------------reLoadPage: $reLoadPage');
      setState(() {});
    }
  }
} // Inner widget end
    
// on Group page a button opens alert dialog 
onPressed: () {
    storage.removeProduct(productData);
    if (!context.mounted) return;
    productDeletedSuccessDialog(context); //opens alert dialog
},

// in alert dialog on confirm it pops back and pass value
onConfirmBtnTap: () {
  debugPrint('product $productData removed');
  Navigator.pop(context, true); // it should pass `true` into InnerWidget (?)
});

p.s. I tried to explain and show the code as strictly and clearly as possible in order to understand the essence of what is happening.

Tags: flutter flutter-navigation

Answers

I have updated the onTapFunction. Once to pop from the second screen, then clause will trigger.

// onTapFunction used and defined in InnerWidget
onTapFunction(BuildContext context, Widget route) async {
    final reLoadPage = await Navigator.push(
      context,
      MaterialPageRoute(
        builder: (context) => route,
      ),
    ).then((value){
      if (reLoadPage ?? false) {
          debugPrint('---------------reLoadPage: $reLoadPage');
          setState(() {});
      }
  });
}

Try like 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(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  MyHomePageState createState() => MyHomePageState();
}

class MyHomePageState extends State<MyHomePage> {
 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Demo'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [InnerWidget()],
        ),
      ),
    );
  }
}

class SecondPage extends StatefulWidget {
  SecondPage({Key? key}) : super(key: key);

  @override
  State<SecondPage> createState() => _SecondPageState();
}

class _SecondPageState extends State<SecondPage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: ElevatedButton(
          onPressed: () {
            Navigator.pop(context, true);
          },
          child: const Text('Go Back'),
        ),
      ),
    );
  }
}

class InnerWidget extends StatefulWidget {
  InnerWidget({Key? key}) : super(key: key);

  @override
  State<InnerWidget> createState() => _InnerWidgetState();
}

class _InnerWidgetState extends State<InnerWidget> {
  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        ElevatedButton(
          onPressed: () async {
            final reLoadPage = await Navigator.push(
              context,
              MaterialPageRoute(
                builder: (context) => SecondPage(),
              ),
            );
            if (reLoadPage ?? false) {
              debugPrint('---------------reLoadPage: $reLoadPage');
              setState(() {});
            }
          },
          child: const Text('Open Page'),
        ),
      ],
    );
  }
}

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The value does not come from the alert window – Flutter

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