CODEWITHSUNDEEP
dartflutter
kar
kar

Reputation: 3651

Unable to change page based on state

New to Flutter and I am using the bottom navigation to switch the page content. Based on debugging, the set state is happening where the correct index number is being captured and assigned to the _selectedPage variable. Yet once I step over that code, the page content remains the same without changing content and the icon 'Home' stays selected in bottom navigation no matter what icon I choose.

Commented parts where I expected a difference when I select a different icon from the nav bar. Please advice. 

import 'package:flutter/material.dart';

class LatestFeed extends StatefulWidget{
  @override
  State<StatefulWidget> createState() => LatestFeedState();
}

class LatestFeedState extends State<LatestFeed>{

  @override
  Widget build(BuildContext context) {

    int _selectedPage = 0;
    List pageOptions = [
      Text('one1', style: TextStyle(fontSize: 36),), // Expecting a change but now it always remains on this data. No change even when set state changes to different index.
      Text('two', style: TextStyle(fontSize: 36),),
      Text('three', style: TextStyle(fontSize: 36),),
      Text('four', style: TextStyle(fontSize: 36),)
    ];

    return MaterialApp(
      home: new Scaffold(
        body: pageOptions[_selectedPage],
        bottomNavigationBar: BottomNavigationBar(
          type: BottomNavigationBarType.fixed,
            items: [
              BottomNavigationBarItem(
                icon: Icon(Icons.home),
                title: Text('Home')
              ),
              BottomNavigationBarItem(
                  icon: Icon(Icons.rss_feed),
                  title: Text('feed')
              ),
              BottomNavigationBarItem(
                  icon: Icon(Icons.featured_play_list),
                  title: Text('list')
              ),
              BottomNavigationBarItem(
                  icon: Icon(Icons.settings),
                  title: Text('settings')
              ),
            ],
            currentIndex: _selectedPage, // expecting different icons to be selected based on this index which is being selected in the set state below. Not seeing any change.
            onTap: (int index){
              setState(() {
                _selectedPage = index; // being assigned correctly yet no effect
              });
            },
        ),
      ),
    );
  }
}

Upvotes: 0

Views: 596

Answers (1)

nonybrighto
nonybrighto

Reputation: 9593

Place your _selectPage and pageOptions in initState or outside your build method to prevent rebuild whenever setState is called 

int _selectedPage;
List<Widget> pageOptions;
    @override
      void initState() {
        super.initState();
         _selectedPage = 0;
        pageOptions = [
          Text('one1', style: TextStyle(fontSize: 36),), // always remains on this data. No change even when set stae changes to different index.
          Text('two', style: TextStyle(fontSize: 36),),
          Text('three', style: TextStyle(fontSize: 36),),
          Text('four', style: TextStyle(fontSize: 36),)
        ];
      }

Whenever you call setState, there will be changes that cause the widgets to rebuild. This means that your build method will be called again. When it gets called, _selectedPage will be set to 0 again and pageOptions[0] will always be the widget selected.

Upvotes: 1

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