flutter/examples/flutter_gallery/lib/demo/material/elevation_demo.dart

import 'package:flutter/material.dart';

class ElevationDemo extends StatefulWidget {
  static const String routeName = '/material/elevation';

  @override
  State<StatefulWidget> createState() => _ElevationDemoState();
}

class _ElevationDemoState extends State<ElevationDemo> {
  bool _showElevation = true;

  List<Widget> buildCards() {
    const List<double> elevations = <double>[
      0.0,
      1.0,
      2.0,
      3.0,
      4.0,
      5.0,
      8.0,
      16.0,
      24.0,
    ];

    return elevations.map((double elevation) {
      return new Center(
        child: new Card(
          margin: const EdgeInsets.all(20.0),
          elevation: _showElevation ? elevation : 0.0,
          child: new SizedBox(
            height: 100.0,
            width: 100.0,
            child: new Center(
              child: new Text('${elevation.toStringAsFixed(0)} pt'),
            ),
          ),
        ),
      );
    }).toList();
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: const Text('Elevation'),
        actions: <Widget>[
          new IconButton(
            icon: const Icon(Icons.sentiment_very_satisfied),
            onPressed: () {
              setState(() => _showElevation = !_showElevation);
            },
          )
        ],
      ),
      body: new ListView(
        children: buildCards(),
      ),
    );
  }
}