Flutter: Building a Cupertino Picker that shows rows containing 2 widgets, from looping through a Map

Question

I've created a picker that displays a Icon and a String, next to each other. The pickers items are taken from a Map I created that contains Key: String and Value: Icon.

In my code right now, I'm using the Cupertino Picker and adding children: [ Row(Icon + String)] but that's quite bad if I want to update them.

I was trying to get a loop going to generate those rows + children but I can't figure out how.

Could someone show me the way or perhaps a more efficient way of getting this result? I'm thinking Extracting row and creating a constructor to input the icon and string, but I'm sure there's a better way...

Here's the code:

Expanded(
                          child: CupertinoPicker(
                            itemExtent: 40,
                            children: <Widget>[
                              Row(
                                mainAxisAlignment: MainAxisAlignment.center,
                                children: <Widget>[
                                  BuildingProblem.problemListIcons[0],
                                  Padding(
                                    padding: EdgeInsets.only(left: 10),
                                    child: Text(
                                      BuildingProblem.problemListNames[0],
                                      style:
                                          TextStyle(color: Colors.white70),
                                    ),
                                  )
                                ],
                              ),
                              Row(
                                mainAxisAlignment: MainAxisAlignment.center,
                                children: <Widget>[
                                  BuildingProblem.problemListIcons[1],
                                  Padding(
                                    padding: EdgeInsets.only(left: 10),
                                    child: Text(
                                      BuildingProblem.problemListNames[1],
                                      style:
                                          TextStyle(color: Colors.white70),
                                    ),
                                  )
                                ],
                              ),
                              Row(
                                mainAxisAlignment: MainAxisAlignment.center,
                                children: <Widget>[
                                  BuildingProblem.problemListIcons[2],
                                  Padding(
                                    padding: EdgeInsets.only(left: 10),
                                    child: Text(
                                      BuildingProblem.problemListNames[2],
                                      style:
                                          TextStyle(color: Colors.white70),
                                    ),
                                  )
                                ],
                              ),
                              Row(
                                mainAxisAlignment: MainAxisAlignment.center,
                                children: <Widget>[
                                  BuildingProblem.problemListIcons[3],
                                  Padding(
                                    padding: EdgeInsets.only(left: 10),
                                    child: Text(
                                      BuildingProblem.problemListNames[3],
                                      style:
                                          TextStyle(color: Colors.white70),
                                    ),
                                  )
                                ],
                              ),
                              Row(
                                mainAxisAlignment: MainAxisAlignment.center,
                                children: <Widget>[
                                  BuildingProblem.problemListIcons[4],
                                  Padding(
                                    padding: EdgeInsets.only(left: 10),
                                    child: Text(
                                      BuildingProblem.problemListNames[4],
                                      style:
                                          TextStyle(color: Colors.white70),
                                    ),
                                  )
                                ],
                              ),
                              Row(
                                mainAxisAlignment: MainAxisAlignment.center,
                                children: <Widget>[
                                  BuildingProblem.problemListIcons[5],
                                  Padding(
                                    padding: EdgeInsets.only(left: 10),
                                    child: Text(
                                      BuildingProblem.problemListNames[5],
                                      style:
                                          TextStyle(color: Colors.white70),
                                    ),
                                  )
                                ],
                              ),
                              Row(
                                mainAxisAlignment: MainAxisAlignment.center,
                                children: <Widget>[
                                  BuildingProblem.problemListIcons[6],
                                  Padding(
                                    padding: EdgeInsets.only(left: 10),
                                    child: Text(
                                      BuildingProblem.problemListNames[6],
                                      style:
                                          TextStyle(color: Colors.white70),
                                    ),
                                  )
                                ],
                              ),
                              Row(
                                mainAxisAlignment: MainAxisAlignment.center,
                                children: <Widget>[
                                  BuildingProblem.problemListIcons[7],
                                  Padding(
                                    padding: EdgeInsets.only(left: 10),
                                    child: Text(
                                      BuildingProblem.problemListNames[7],
                                      style:
                                          TextStyle(color: Colors.white70),
                                    ),
                                  )
                                ],
                              )
                            ],
                            onSelectedItemChanged: (int index) {
                              print('good boi');
                            },
                            looping: true,
                            backgroundColor: Color(0xff2e3032),
                          ),
                        ),

How it looks like:

Solution

You can copy paste run full code below
You can use control-flow-collections

code snippet

children: <Widget>[
                  for (var i = 0;
                      i < BuildingProblem.problemListIcons.length;
                      i++)
                    Row(
                      mainAxisAlignment: MainAxisAlignment.center,
                      children: <Widget>[
                        BuildingProblem.problemListIcons[i],
                        Padding(
                          padding: EdgeInsets.only(left: 10),
                          child: Text(
                            BuildingProblem.problemListNames[i],
                            style: TextStyle(color: Colors.white70),
                          ),
                        )
                      ],
                    ),
                ],

working demo

You need to add file analysis_options.yaml to root of your project and the following line

analyzer:
  enable-experiment:
    - control-flow-collections

full code

import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class BuildingProblem {
  static List<Icon> problemListIcons = [];
  static List<String> problemListNames = [];
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  void initState() {
    BuildingProblem.problemListIcons.add(Icon(Icons.add));
    BuildingProblem.problemListIcons.add(Icon(Icons.cast));
    BuildingProblem.problemListNames.add("add");
    BuildingProblem.problemListNames.add("cast");
    // TODO: implement initState
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Expanded(
              child: CupertinoPicker(
                itemExtent: 40,
                children: <Widget>[
                  for (var i = 0;
                      i < BuildingProblem.problemListIcons.length;
                      i++)
                    Row(
                      mainAxisAlignment: MainAxisAlignment.center,
                      children: <Widget>[
                        BuildingProblem.problemListIcons[i],
                        Padding(
                          padding: EdgeInsets.only(left: 10),
                          child: Text(
                            BuildingProblem.problemListNames[i],
                            style: TextStyle(color: Colors.white70),
                          ),
                        )
                      ],
                    ),
                ],
                onSelectedItemChanged: (int index) {
                  print('good boi');
                },
                looping: true,
                backgroundColor: Color(0xff2e3032),
              ),
            ),
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

Comments

[MoofinTheExplorer]

This works! Could you explain to me though why I had to add the control-flow-collections? I believe Flutter gave me a notification to update SDK and that did it for me, so now it works, but I'm trying to understand your solution as well as I can so that I can learn from it.

[chunhunghan]

control-flow-collections is under experiment. In my environment , I need to do it manually. I use master channel. it's just a notice. because I did not get notification to update SDK

[MoofinTheExplorer]

I see, this is my first app and my first coding language so I'm trying to make sense of it all as I go!