samples/web/charts/lib/behaviors/initial_selection.dart

// Copyright 2018 the Charts project authors. Please see the AUTHORS file
// for details.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

/// Example of adding an initial selection behavior.
///
/// This example adds initial selection to a bar chart, but any chart can use
/// the initial selection behavior.
///
/// Initial selection is only set on the very first draw and will not be set
/// again in subsequent draws unless the behavior is reconfigured.
///
/// The selection will remain on the chart unless another behavior is added
/// that updates the selection.

// EXCLUDE_FROM_GALLERY_DOCS_START
import 'dart:math';
// EXCLUDE_FROM_GALLERY_DOCS_END
import 'package:charts_flutter/flutter.dart' as charts;
import 'package:flutter/material.dart';

class InitialSelection extends StatelessWidget {
  final List<charts.Series<dynamic, String>> seriesList;
  final bool? animate;

  const InitialSelection(this.seriesList, {this.animate, Key? key})
      : super(key: key);

  /// Creates a [BarChart] with initial selection behavior.
  factory InitialSelection.withSampleData() {
    return InitialSelection(
      _createSampleData(),
      // Disable animations for image tests.
      animate: false,
    );
  }

  // EXCLUDE_FROM_GALLERY_DOCS_START
  // This section is excluded from being copied to the gallery.
  // It is used for creating random series data to demonstrate animation in
  // the example app only.
  factory InitialSelection.withRandomData() {
    return InitialSelection(_createRandomData());
  }

  /// Create random data.
  static List<charts.Series<OrdinalSales, String>> _createRandomData() {
    final random = Random();

    final data = [
      OrdinalSales('2014', random.nextInt(100)),
      OrdinalSales('2015', random.nextInt(100)),
      OrdinalSales('2016', random.nextInt(100)),
      OrdinalSales('2017', random.nextInt(100)),
    ];

    return [
      charts.Series<OrdinalSales, String>(
        id: 'Sales',
        colorFn: (_, __) => charts.MaterialPalette.blue.shadeDefault,
        domainFn: (OrdinalSales sales, _) => sales.year,
        measureFn: (OrdinalSales sales, _) => sales.sales,
        data: data,
      )
    ];
  }
  // EXCLUDE_FROM_GALLERY_DOCS_END

  @override
  Widget build(BuildContext context) {
    return charts.BarChart(
      seriesList,
      animate: animate,
      behaviors: [
        // Initial selection can be configured by passing in:
        //
        // A list of datum config, specified with series ID and domain value.
        // A list of series config, which is a list of series ID(s).
        //
        // Initial selection can be applied to any chart type.
        //
        // [BarChart] by default includes behaviors [SelectNearest] and
        // [DomainHighlighter]. So this behavior shows the initial selection
        // highlighted and when another datum is tapped, the selection changes.
        charts.InitialSelection(selectedDataConfig: [
          charts.SeriesDatumConfig<String>('Sales', '2016')
        ])
      ],
    );
  }

  /// Create one series with sample hard coded data.
  static List<charts.Series<OrdinalSales, String>> _createSampleData() {
    final data = [
      OrdinalSales('2014', 5),
      OrdinalSales('2015', 25),
      OrdinalSales('2016', 100),
      OrdinalSales('2017', 75),
    ];

    return [
      charts.Series<OrdinalSales, String>(
        id: 'Sales',
        colorFn: (_, __) => charts.MaterialPalette.blue.shadeDefault,
        domainFn: (OrdinalSales sales, _) => sales.year,
        measureFn: (OrdinalSales sales, _) => sales.sales,
        data: data,
      )
    ];
  }
}

/// Sample ordinal data type.
class OrdinalSales {
  final String year;
  final int sales;

  OrdinalSales(this.year, this.sales);
}