flutter/examples/platform_services/lib/main.dart

// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'dart:async';
import 'dart:io';

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

class PlatformServices extends StatefulWidget {
  @override
  _PlatformServicesState createState() => new _PlatformServicesState();
}

class _PlatformServicesState extends State<PlatformServices> {
  static const PlatformMethodChannel platform = const PlatformMethodChannel('battery');
  String _batteryLevel = 'Unknown battery level.';

  Future<Null> _getBatteryLevel() async {
    String batteryLevel;
    if (Platform.isIOS) {
      batteryLevel = "iOS is not supported yet.";
    } else {
      try {
        final int result = await platform.invokeMethod('getBatteryLevel');
        batteryLevel = 'Battery level at $result. %';
      } on PlatformException catch (e) {
        batteryLevel = "Failed to get battery level: '${e.message}'.";
      }
    }
    setState(() {
      _batteryLevel = batteryLevel;
    });
  }

  @override
  Widget build(BuildContext context) {
    return new Material(
      child: new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
          children: <Widget>[
            new RaisedButton(
              child: new Text('Get Battery Level'),
              onPressed: _getBatteryLevel,
            ),
            new Text(_batteryLevel)
          ],
        )
      )
    );
  }
}
  
void main() {
  runApp(new PlatformServices());
}