A non-null String must be provided to a Text widget

Question

I'm trying to add the option for the quantity to be adjusted but I get an error saying "A non-null String must be provided to a Text widget" How do I provide this, to this code?

 trailing: Container(
        height: 60,
        width: 60,
        padding: EdgeInsets.only(left: 10),
        child: Column(
          children: <Widget>[
            new GestureDetector(child: Icon(Icons.arrow_drop_up), onTap: () {}),
            new Text(cart_prod_qty),
            new GestureDetector(child: Icon(Icons.arrow_drop_down), onTap: () {})
          ],
        ),

@FellipeMalta Not a good ideia. It won't fail on run but the text is going to show "null", instead. — Hugo Passos, May 29 '19 at 00:36
I thought the variable has already been declared, was just a thought @HugoPassos — Fellipe Malta, May 29 '19 at 01:02
It showed null. The cart_prod_qty has been declared as 1. But also the first error came back https://i.stack.imgur.com/PSIH4.png — Mm Victory, May 29 '19 at 01:24
Where is `cart_prod_qty` defined? Clearly that is `null` and not `1` as you expect, but you don't show it anywhere. You need to provide more code. — Herohtar, May 29 '19 at 01:27
Here https://i.stack.imgur.com/aSQg0.png and the rest of the code is here i.stack.imgur.com/m180K.png i.stack.imgur.com/bbCsp.png i.stack.imgur.com/v4iQ0.png — Mm Victory, May 29 '19 at 01:38
Please don't use images for posting code. Extract the main part and put it in the question. If it's absolutely need to send big part of code, consider posting it on [gist](https://gist.github.com/) or [pastebin](https://pastebin.com/) and sending link here — Pavel, May 29 '19 at 01:45
You need to edit your question and actually copy and paste the code **as text** into it. Also, your error is a simple typo. — Herohtar, May 29 '19 at 03:07

score 43 · Answer 1 · edited Nov 08 '19 at 07:20

43

You should check null safe

Text(cart_prod_qty??'default value'),

edited Nov 08 '19 at 07:20

Ravinder Kumar

7,407
3
28
54

answered May 29 '19 at 04:52

Nikhil Vadoliya

1,542
10
17

And I'd like to add: In flutter, it often makes sense to *not* create a `Text` widget in this case, e.g. in all kinds of `Tiles` and other stuff: `Tile(..., subtitle: cart_prod_qty == null ? null : Text(cart_prod_qty)),` This will render more nicely because it has no empty `Text` widget around. – rgisi Dec 01 '20 at 10:41
Helped me understand my dumb mistake. – Gaurav Joseph Feb 07 '21 at 21:20
best answer..... – Rahul Kushwaha Jan 11 '22 at 11:28

score 9 · Answer 2 · edited Nov 08 '19 at 09:58

9

Just check for null and give a default

Text(cart_prod_qty!=null?cart_prod_qty:'default value'),

You can keep it empty if you wish

Text(cart_prod_qty!=null?cart_prod_qty:''),

Or else you can make text widget optional

cart_prod_qty!=null? Text(cart_prod_qty): Container()

edited Nov 08 '19 at 09:58

Ravinder Kumar

7,407
3
28
54

answered May 29 '19 at 04:45

Praneeth Dhanushka Fernando

3,033
2
18
19

score 5 · Answer 3 · answered Aug 06 '19 at 18:43

The error itself shows what's wrong in the code, Text widget works only with string and for null they intentionally have thrown an exception. Check text.dart file implementation where they added throwing an exception.

assert(
         data != null,
         'A non-null String must be provided to a Text widget.',
       ),

To solve above error you have to provide some default text.

new Text(cart_prod_qty!=null?cart_prod_qty:'Default Value'),

score 4 · Answer 4 · answered Mar 21 '21 at 23:41

4

An advice for you in this case and all who are reading this.

When you add an non direct String value to the Text() don't directly insert it like you did in this example:

Text(cart_prod_qty)

Because you can get "A non-null String must be provided to a Text widget" like I did.

So I advise you to practice this in the future it's more safe:

Text('${cart_prod_qty}')

answered Mar 21 '21 at 23:41

NiiTii

237
6
25

Thank you alot, you save my soul, really informative – Abhishek Chhabra Jul 31 '21 at 17:41

score 4 · Answer 5 · answered May 28 '21 at 18:31

4

if you know for certain that it's not null, then you can safely do this:

Text(cart_prod_qty!),

to me, when it's definitely not null in the usage case, it's cleaner than doing this:

Text(cart_prod_qty ?? ''),

answered May 28 '21 at 18:31

Matthew Kooshad

186
13

score 3 · Answer 6 · answered Nov 08 '19 at 06:51

3

The value may be empty therefore youre getting a null error try this if its an optional field:

new Text(cart_prod_qty == null ? '' : cart_prod_qty),

answered Nov 08 '19 at 06:51

score 2 · Answer 7 · answered Mar 15 '21 at 05:02

If you know that your string is nullable you could do something like this. Although I used the visibility widget because I don't want my widget to be displayed if it's null.

class NullableTextWidget extends StatelessWidget {
      final String? text;
      final TextStyle? textStyle;
      const NullableTextWidget({Key? key, this.text,this.textStyle}) : super(key: key);
    
      @override
      Widget build(BuildContext context) {
        return Visibility(
          visible: text != null,
          child: Text(
            text ?? "",
            style: textStyle,),
        );
      }
    }

score 0 · Answer 8 · answered Mar 04 '20 at 17:25

0

just set Text widget value optional like

Text(value ?? ""),

answered Mar 04 '20 at 17:25

Akshay I

3,675
1
34
57

score 0 · Answer 9 · answered Oct 21 '20 at 18:13

The problem is visible. You're passing null to Text widget. new Text(cart_prod_qty) This can be due to delay of response from api (if you're using it). Or there is no value in the variable "cart_prod_qty". You can handle it like this: new Text(cart_prod_qty != null ? cart_prod_qty.toString : '')

score 0 · Answer 10 · answered Jun 06 '22 at 07:09

I faced the same problem while fetching data from Firebase . It was initially: Text(widget.title) - it caused the error .

Later, I transformed the Text() into this format: Text('${widget.title}')

this interpolates the fetched data inside the Text() widget .

If you receive a null value return , that would be a server issue .

Hope this might help someone .

score -1 · Answer 11 · answered Dec 21 '20 at 06:04

-1

I have faced that same problem.... I have resolved it by using a "new" keyword before Text...

child: new Text(mydata[1]["2"][k]),

answered Dec 21 '20 at 06:04

Samrat Mukherjee

1

Could you exaplain more details with your answer. – YLR Dec 21 '20 at 06:14

score -2 · Answer 12 · answered Nov 08 '19 at 05:19

-2

I GOT SAME ERROR DUE TO THIS

BEFORE:

title:  Text(widget.title)

AFTER:

title:  Text('ram')

THIS SOLVED MY ERROR

To solve this error Add Double quote or single quote title: Text('ram')

answered Nov 08 '19 at 05:19

raman raman

1,655
4
22
34

A non-null String must be provided to a Text widget

12 Answers12

Linked