Modify array from TextField in Flutter

Question

I have this simple widget showing a textfield from which I modify a List:

Widget _elementTextField() {
    final TextEditingController inputNewElement = new TextEditingController();
    return Expanded(
      flex: 3,
      child: Padding(
        padding: EdgeInsets.fromLTRB(0, 16.0, 16.0, 16.0),
        child: Container(
          child: TextField(
            controller: inputNewElement,
            decoration: InputDecoration(labelText: "Add Element"),
            onSubmitted: (elem) {
              // method 1 to update UI
              /*setState(() {
                newSet.elements.add(elem);
              });*/
              // method 2 not updating UI
              // newSet.elements.add(elem);

              print(newSet.elements);
              inputNewElement.clear();
            },
          ),
        ),
      ),
    );
  }

If I uncomment any of those method I won't see the print and the input won't clean up.

This is not related to any other widget and the List is just a simple List with one value on it.

This works fine with other widget I have but on that case I modify the value on a global provider. This is using just a StateFul widget

the whole widget is quite big cause includes a swiper with different widgets in it. I moved the controller inside class _NewSetPageState extends State<NewSetPage> { which is the main one and this loads _elementTextField() — Dani
– Dani, Commented Jan 14, 2020 at 11:51
It's confusing just to see half code, you see. if possible just create a mini version of your widget which reproduces the same problem... so that we can help you out properly. — Harshvardhan Joshi
– Harshvardhan Joshi, Commented Jan 14, 2020 at 12:02
makes sense. Let me create a smaller version and I'll share the whole thing — Dani
– Dani, Commented Jan 14, 2020 at 12:27

Hian · Accepted Answer · 2020-01-14 12:28:19Z

1

Try to remove final TextEditingController inputNewElement = new TextEditingController(); from _elementTextField()

import 'package:flutter/material.dart';

class SamplePage extends StatefulWidget {

    SamplePage({Key key}) : super(key: key);

    @override
    State<StatefulWidget> createState() => SamplePageState();

}

class SamplePageState extends State<SamplePage> {

    final List<String> list = List();
    final TextEditingController inputNewElement = new TextEditingController();

    @override
    void initState() {
        super.initState();
    }

    @override
    void dispose() {
        inputNewElement.dispose();
        super.dispose();
    }

    @override
    Widget build(BuildContext context) {
        return Scaffold(
            body: Column(
                children: <Widget>[
                    Row(children: <Widget>[_elementTextField()]),
                    Text(list.isEmpty ? 'Empty' : list.toString()),
                ],
            )
        );
    }

    Widget _elementTextField() {
//        final TextEditingController inputNewElement = new TextEditingController();
        return Expanded(
            flex: 3,
            child: Padding(
                padding: EdgeInsets.fromLTRB(0, 16.0, 16.0, 16.0),
                child: Container(
                    child: TextField(
                        controller: inputNewElement,
                        decoration: InputDecoration(labelText: "Add Element"),
                        onSubmitted: (elem) {
                            setState(() {
                                list.add(elem);
                            });
                            print(list);
                            inputNewElement.clear();
                        },
                    ),
                ),
            ),
        );
    }

}

edited Jan 14, 2020 at 12:28

answered Jan 14, 2020 at 10:38

Hian

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2 Comments

Dani Over a year ago

I moved the controller as you suggested and try both method and none of them worked

Hian Over a year ago

I have updated my post and add more detail, basically a widget. Please, avoid call _elementTextField() inside Column because it will stretch vertically

Harshvardhan Joshi · Accepted Answer · 2020-01-14 11:12:08Z

1

TextField itself is a Stateful widget, so when you call setState from inside the methods in TextField it will not update widgets outside of the text field.

To resolve this create the method in the parent widget to update the list and call setState from there, it will update the parent widget and the text field will be cleared.

answered Jan 14, 2020 at 11:12

Harshvardhan Joshi

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Comments

Harshvardhan Joshi · Accepted Answer · 2020-01-15 09:41:57Z

1

You'll find the solution above this answer, this was just my approaches to fix the whole problem:

Trying to recreate a smaller version of my page, I found this issue:

@override
  Widget build(BuildContext context) {
   if (widget.data != null) {
      // editing set
      newSet.elements = widget.data['mySet']['elements'];
    } else {
      // creating set
      ...
    }

This was executed every time I added something to the array so I moved the check to initState().

Second error was this:

newSet.elements = widget.data['mySet']['elements'];

I had to modify this line and create my list without cloning it like so:

newSet.elements = []..addAll(widget.data['mySet']['elements']);

At this point, my list was adding more elements but it wasn't being displayed (I didn't mention this issue but I'll show the solution anyway).

I had this var containing some widgets:

_steps = [
      _step0(),
      _step1(),
      _step2(),
    ];

This list was being used to change dynamically a Swiper widget (more info).

So instead of doing this:

Swiper(
    itemBuilder: (BuildContext context, int index) {
       return _steps[index];
    },

I do this now:

    Swiper(
        itemBuilder: (BuildContext context, int index) {
              switch (index) {
                    case 1:
                      return _step1();
                      break;
                    case 2:
                      return _step2();
                      break;
                    default:
                      return _step0();
                  }
        },

edited Jan 15, 2020 at 9:41

Harshvardhan Joshi

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answered Jan 14, 2020 at 23:25

Dani

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1 Comment

Harshvardhan Joshi Over a year ago

the last change makes sense, as the widgets in the list are built only once when the list is built, but in switch case it builds every time the case is executed... awesome debugging, bro.

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