How to render list inside list in flutter?

Question

I'm creating an flutter app which should show list of teams, and each team is an object with items like

name: string

players: array of

name: string

so it looks like this

List teams = [
      {
        'name': 'Team one',
        'players': [
          {
            'name': 'Team one player one',
          },
          {
            'name': 'Team one player two',
          },
          {
            'name': 'Team one player three',
          },
        ]
      },
      {
        'name': 'Team two',
        'players': [
          {
            'name': 'Team two player one',
          },
          {
            'name': 'Team two player one',
          },
          {
            'name': 'Team two player three',
          },
        ]
      },
    ];

Further, in my code, I'm iterating through all teams with ListView, like this

  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        child: renderTeams(teams),
      ),
    );
  }

and renderTeams() looks like this:

  Widget renderTeams(List teams) {
    return ListView.builder(
      itemCount: teams.length,
      itemBuilder: (context, index) {
        return Padding(
          padding: EdgeInsets.all(10.0),
          child: Column(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            mainAxisSize: MainAxisSize.min,
            children: [
              Text(teams[index]['name']),
              Row(
                children: <Widget>[
                  Flexible(
                    child: PlayerCard(
                      player: teams[index]['players'][0],
                    ),
                  ),
                  Flexible(
                    child: PlayerCard(
                      player: teams[index]['players'][1],
                    ),
                  ),
                  Flexible(
                    child: PlayerCard(
                      player: teams[index]['players'][2],
                    ),
                  ),
                ],
              )
            ],
          ),
        );
      },
    );
  }

This works well, everything gets rendered accordingly.

However, I'd like to, instead adding each player separately, iterate through each's team players, so my renderTeams() would look like this:

  Widget renderTeams(List teams) {
    return ListView.builder(
      itemCount: teams.length,
      itemBuilder: (context, index) {
        return Padding(
          padding: EdgeInsets.all(10.0),
          child: Column(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            mainAxisSize: MainAxisSize.min,
            children: [
              Text(teams[index]['name']),
              renderPlayers(teams[index]['players'])
            ],
          ),
        );
      },
    );
  }

and renderPlayers() looks like this:

  renderPlayers(players) {
    return Row(children: players.map((player) => {
        Flexible(
          child: PlayerCard(
            player: player,
          ),
      )
    }).toList());
  }

This is where my troubles begin, as I'm getting errors like

type 'List<dynamic>' is not a subtype of type 'List<Widget>'

And I've googled around, but other responses, tried to fix types, but that leads me into infinite loop of trying to fix errors i do not understand.

Anyone got any hint? Thanks in advance

Michael Yuwono · Accepted Answer · 2019-05-20 10:25:36Z

6

Remove { }

renderPlayers(players) {
  return Row(children: players.map((player) => 
      Flexible(
        child: PlayerCard(
          player: player,
      ),
    )
  ).toList());
}

Explanation

=> means return. => { ... } means returning a function (dynamic). That's why it was detected as List<dynamic>

answered May 20, 2019 at 10:25

Michael Yuwono

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3 Comments

Uros Over a year ago

Thanks for helping, but this is not working. I'm getting same error as above.

Uros Over a year ago

Although, on the second try, your answer opened another set of possibilities for me, and by using your code and just adding List before parameter players, it worked. Thank you so much!

Nabin Dhakal Over a year ago

please help me with this stackoverflow.com/questions/60432234/…

Abdur Rehman · Accepted Answer · 2023-01-20 12:03:18Z

-1

Use Spread Operator [...]

The best solution for this type of problem is the Spreed Operator [...]. The spread operator combines two or more list instances. It also extends a collection's elements of a such as a list. You can use it with Columns, Rows or Listview. Like this:

// List
final variableValuesList = [
VariablesWithValues(
 title: 'a',
 value: 1,
),
VariablesWithValues(
 title: 'b',
 value: 1,
),
];

  /// using inside column
  Column(
   children: [
     ///getting values from the list through spread operator
    ...variableValuesList.map((item) => Text(${item.title} = ${item.value})
      ).toList(),

answered Jan 20, 2023 at 12:03

Abdur Rehman

5756 silver badges6 bronze badges

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