build method

  1. @override
Widget build(
  1. BuildContext context,
  2. WidgetRef ref
)
override

Describes the part of the user interface represented by this widget.

The framework calls this method when this widget is inserted into the tree in a given BuildContext and when the dependencies of this widget change (e.g., an InheritedWidget referenced by this widget changes). This method can potentially be called in every frame and should not have any side effects beyond building a widget.

The framework replaces the subtree below this widget with the widget returned by this method, either by updating the existing subtree or by removing the subtree and inflating a new subtree, depending on whether the widget returned by this method can update the root of the existing subtree, as determined by calling Widget.canUpdate.

Typically implementations return a newly created constellation of widgets that are configured with information from this widget's constructor and from the given BuildContext.

The given BuildContext contains information about the location in the tree at which this widget is being built. For example, the context provides the set of inherited widgets for this location in the tree. A given widget might be built with multiple different BuildContext arguments over time if the widget is moved around the tree or if the widget is inserted into the tree in multiple places at once.

The implementation of this method must only depend on:

If a widget's build method is to depend on anything else, use a StatefulWidget instead.

See also:

  • StatelessWidget, which contains the discussion on performance considerations.

Implementation

@override
Widget build(BuildContext context, WidgetRef ref) {
  final randomPartition = ref.watch(randomPartitionSettingProvider);

  Future<void> saveRandomSeed(int value) async {
    final prefs = await SharedPreferences.getInstance();

    // Save "Random Seed" state to preferences.

    await prefs.setInt('randomSeed', value);
  }

  Future<void> saveRandomPartition(bool value) async {
    final prefs = await SharedPreferences.getInstance();

    // Save "Random Partition" state to preferences.

    await prefs.setBool('randomPartition', value);
  }

  return Column(
    children: [
      Row(
        children: [
          NumberField(
            label: 'Random Seed',
            key: const Key('random_seed_settings'),
            tooltip: '''

            **Random Seed:** The random seed is used to control the randomness
            of partitioning the dataset and building models.  Setting a
            specific seed ensures that results are reproducible. The random
            seed will be reset to this value each time the dataset is
            partitioned or the model is built.

            ''',
            controller: controller,
            inputFormatter: FilteringTextInputFormatter.digitsOnly,
            validator: (value) => validateInteger(value, min: 1),
            stateProvider: randomSeedSettingProvider,
            sharedPrefsKey: 'randomSeed',
          ),
          configRowGap,
          const Text(
            'Random Partition each Model Build',
            style: TextStyle(fontSize: 16),
          ),
          configRowGap,
          MarkdownTooltip(
            message: '''

            **Random Partition each Model Build:** When enabled, the dataset
            partition (if any) will be reset and randomised each time a model
            is built.  This is useful if you want to ensure that the model is
            not biased towards a specific partition. If this is disabled then
            the same partition is used for each model build and so the dame
            model is built each time.

            ''',
            child: Switch(
              value: randomPartition,
              onChanged: (value) {
                ref.read(randomPartitionSettingProvider.notifier).state =
                    value;
                saveRandomPartition(value);
              },
            ),
          ),
          configRowGap,
          MarkdownTooltip(
            message: '''

            **Reset Random Seed:** Tap here to factory reset the random seed
            settings to their default values, being 42 for the seed itself and
            to retain the same partitioning for building a model.

            ''',
            child: ElevatedButton(
              onPressed: () {
                ref.read(randomSeedSettingProvider.notifier).state =
                    defaultRandomSeed;
                saveRandomSeed(defaultRandomSeed);

                ref.read(randomPartitionSettingProvider.notifier).state =
                    false;
                saveRandomPartition(false);
              },
              child: const Text('Reset'),
            ),
          ),
        ],
      ),
    ],
  );
}