How to dynamically insert and remove widgets based on demand in flutter?

Question

The question is common. However, I tried to simulate the event by adding a Container to the Column on tapping a button. But, the container is not added to the Column or not getting rendered on the screen. In addition to that, the setState method shows a warning that it isn't referenced.

here is the code

import 'package:flutter/material.dart';
import 'package:focus7/Configurations/size_config.dart';

class Demo2 extends StatefulWidget {
  @override
  _Demo2State createState() => _Demo2State();
}

class _Demo2State extends State<Demo2> {
  List<Widget> containersList = [
    Container(
      color: Colors.amberAccent,
      height: 100,
      width: 200,
    ),
    Container(
      color: Colors.red,
      height: 100,
      width: 200,
    ),
    Container(
      color: Colors.brown,
      height: 100,
      width: 200,
    ),
    Container(
      color: Colors.green,
      height: 100,
      width: 200,
    ),
  ];
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: SafeArea(
      child: Column(children: <Widget>[
        ...containersList,
        RaisedButton(
          onPressed: () {
            setState() => containersList.add(Container(
                  color: Colors.lightBlue,
                  height: 100,
                  width: 200,
                ));
          },
          child: Text("click"),
        )
      ]),
    ));
  }
}

here is the output:

Viren V Varasadiya · Accepted Answer · 2020-04-11 17:15:03Z

2

The problem is that you are using arrow function, which mean whatever you are writing in right side is gonna return something and you are not assigning it to any variable which is not actual requirement too, and that's why it is showing error.

Replace your setState with following one while solve your issue.

setState(() {
              containersList.add(Container(
                color: Colors.lightBlue,
                height: 100,
                width: 200,
              ));
            });

answered Apr 11, 2020 at 17:15

Viren V Varasadiya

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1 Comment

Bala Ganesh Over a year ago

Hey, thanks for the response, it's working perfectly.

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