CODEWITHSUNDEEP
androidioslistflutterdart
user9047282
user9047282

Reputation:

Flutter - The getter 'length' was called on null

I am trying to develop a flutter app. This flutter is creating teams for a card game. After the creation of the team, the points could be counted through the, so that you don't have to think about how many points everybody has.

But I got an exception, where I know where the exception and what it means, but i do not have any clue how i could solve the problem. I hope some of you guys could help me.

This is the code where the error is thrown:

import 'package:flutter/material.dart';


class Punktezaehler extends StatefulWidget{

  final List<String> spieler_namen;
  Punktezaehler(this.spieler_namen);

  @override
  State<StatefulWidget> createState() => new _Punktezaehler(this.spieler_namen);
}


class _Punktezaehler extends State<Punktezaehler>{

  final List<String> spieler_namen;
  _Punktezaehler(this.spieler_namen);

  List<int> punkteanzahl_teamEins;
  List<int> punkteanzahl_teamZwei;

  @override
  Widget build(BuildContext context) {


    var spieler1 = spieler_namen[0].substring(0,3);
    var spieler2 = spieler_namen[1].substring(0,3);
    var spieler3 = spieler_namen[2].substring(0,3);
    var spieler4 = spieler_namen[3].substring(0,3);

    return new Scaffold(
      appBar: new AppBar(
        automaticallyImplyLeading: false,
        title: new Text("$spieler1 & $spieler2 vs" +" $spieler3 & $spieler4"),
        actions: <Widget>[

        ],
      ),
      body: Container(
        child: new Row(
          children: <Widget>[
            new Column(
              children: <Widget>[
                new IconButton(
                    icon: Icon(Icons.exposure_plus_2),
                    onPressed: () => punkte_hinzuzaehlen(1, 2)
                )
              ],
            ),
            new Column(
              children: <Widget>[
                //new FlatButton(onPressed: () => print(punkteanzahl_teamEins.length), child: new Text("Punkte")),
                ListView.builder(
                  itemCount: punkteanzahl_teamEins.length, //--> Error is thrown here
                  itemBuilder: (context, index){
                    return Text(punkteanzahl_teamEins[index].toString());
                  }
                ),
                new Row()
              ],
            ),
            new Column(
              children: <Widget>[
                new IconButton(
                    icon: Icon(Icons.exposure_plus_2),
                    onPressed: () => punkte_hinzuzaehlen(2, 2)
                )],
            )
          ],
        )
      ),
    );
  }

  void punkte_hinzuzaehlen(int team, int nummer){
    if (team == 1){
      //Team 1 bekommt die Punkte
      print("Team 1 gets points");
    }
    else if(team == 2){
      //Team 2 bekommt die Punkte
      print("Team 2 gets points");
    }
  }
}

And this is the error message:

══╡ EXCEPTION CAUGHT BY GESTURE ╞═══════════════════════════════════════════════════════════════════
I/flutter (26028): The following NoSuchMethodError was thrown while handling a gesture:
I/flutter (26028): The getter 'length' was called on null.
I/flutter (26028): Receiver: null
I/flutter (26028): Tried calling: length

After the fix, I got another error:

══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter (26028): The following assertion was thrown during performResize():
I/flutter (26028): Vertical viewport was given unbounded width.
I/flutter (26028): Viewports expand in the cross axis to fill their container and constrain their children to match
I/flutter (26028): their extent in the cross axis. In this case, a vertical viewport was given an unlimited amount of
I/flutter (26028): horizontal space in which to expand.

Upvotes: 10

Views: 91239

Answers (7)

Samir Patel
Samir Patel

Reputation: 61

If you called api in your project. check your device network connection. try to re start your simulator. that will fix this error.

Upvotes: 0

Dieudonn&#233; Miyalu
Dieudonn&#233; Miyalu

Reputation: 1

Initialize your list, and run hot restart (press R).

It works correctly.

Upvotes: 0

Robert Stevens
Robert Stevens

Reputation: 549

I fix this by revisiting this section in pubspec.yaml

# To add assets to your application, add an assets section, like this:
# assets:
#  - images/a_dot_burr.jpeg
#  - images/a_dot_ham.jpeg

Ensure your spacing, hyphens and filenames are correct. Note: You do not need to list every image file; instead, you can just list their directory:

assets:
- images/

Upvotes: -1

Aloti
Aloti

Reputation: 67

In our case, we got this error when Internet Connection is off after calling webservice.

Upvotes: 2

Adam
Adam

Reputation: 444

First one check spieler_namen is null or not.If it is null then use below code i hope this will solve your problem.....

if(spieler_namen == null){
  new Container(width: 10.0,height:  10.0,);
 }else{
 your requirement .......
 }

Upvotes: 2

Chetan Raval
Chetan Raval

Reputation: 51

We spend lost's of time to resolve issue finally we got a solution is: Please check you pubspec.yaml and remove extra '-' in case of assets file and also please follow the structure of that like spacing and all that.

We are must sure that issue only in pubspec.yaml file

Upvotes: 2

Dhiraj Sharma
Dhiraj Sharma

Reputation: 4859

punkteanzahl_teamEins is only declared. But not initialized. So it is throwing null error.

You should assign value to punkteanzahl_teamEins as

List<int> punkteanzahl_teamEins = [1,4,5,7];

or pass data from parent as requirement.

Upvotes: 13

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