samples/web/charts/example/lib/pie_chart/auto_label.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.

/// Donut chart with labels example. This is a simple pie chart with a hole in
/// the middle.
// EXCLUDE_FROM_GALLERY_DOCS_START
import 'dart:math';
// EXCLUDE_FROM_GALLERY_DOCS_END
import 'package:charts_flutter/flutter.dart' as charts;
import 'package:flutter_web/material.dart';

class DonutAutoLabelChart extends StatelessWidget {
  final List<charts.Series> seriesList;
  final bool animate;

  DonutAutoLabelChart(this.seriesList, {this.animate});

  /// Creates a [PieChart] with sample data and no transition.
  factory DonutAutoLabelChart.withSampleData() {
    return new DonutAutoLabelChart(
      _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 DonutAutoLabelChart.withRandomData() {
    return new DonutAutoLabelChart(_createRandomData());
  }

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

    final data = [
      new LinearSales(0, random.nextInt(100)),
      new LinearSales(1, random.nextInt(100)),
      new LinearSales(2, random.nextInt(100)),
      new LinearSales(3, random.nextInt(100)),
    ];

    return [
      new charts.Series<LinearSales, int>(
        id: 'Sales',
        domainFn: (LinearSales sales, _) => sales.year,
        measureFn: (LinearSales sales, _) => sales.sales,
        data: data,
        // Set a label accessor to control the text of the arc label.
        labelAccessorFn: (LinearSales row, _) => '${row.year}: ${row.sales}',
      )
    ];
  }
  // EXCLUDE_FROM_GALLERY_DOCS_END

  @override
  Widget build(BuildContext context) {
    return new charts.PieChart(seriesList,
        animate: animate,
        // Configure the width of the pie slices to 60px. The remaining space in
        // the chart will be left as a hole in the center.
        //
        // [ArcLabelDecorator] will automatically position the label inside the
        // arc if the label will fit. If the label will not fit, it will draw
        // outside of the arc with a leader line. Labels can always display
        // inside or outside using [LabelPosition].
        //
        // Text style for inside / outside can be controlled independently by
        // setting [insideLabelStyleSpec] and [outsideLabelStyleSpec].
        //
        // Example configuring different styles for inside/outside:
        //       new charts.ArcLabelDecorator(
        //          insideLabelStyleSpec: new charts.TextStyleSpec(...),
        //          outsideLabelStyleSpec: new charts.TextStyleSpec(...)),
        defaultRenderer: new charts.ArcRendererConfig(
            arcWidth: 60,
            arcRendererDecorators: [new charts.ArcLabelDecorator()]));
  }

  /// Create one series with sample hard coded data.
  static List<charts.Series<LinearSales, int>> _createSampleData() {
    final data = [
      new LinearSales(0, 100),
      new LinearSales(1, 75),
      new LinearSales(2, 25),
      new LinearSales(3, 5),
    ];

    return [
      new charts.Series<LinearSales, int>(
        id: 'Sales',
        domainFn: (LinearSales sales, _) => sales.year,
        measureFn: (LinearSales sales, _) => sales.sales,
        data: data,
        // Set a label accessor to control the text of the arc label.
        labelAccessorFn: (LinearSales row, _) => '${row.year}: ${row.sales}',
      )
    ];
  }
}

/// Sample linear data type.
class LinearSales {
  final int year;
  final int sales;

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