Flutter_Side.dart

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

class BatteryLevel extends StatefulWidget {
  @override
  _BatteryLevelState createState() => _BatteryLevelState();
}

class _BatteryLevelState extends State<BatteryLevel> {
  static const platform = MethodChannel('battery');
  String batteryLevel = 'Unknown';

  Future<void> getBatteryLevel() async {
    try {
      final int result = await platform.invokeMethod('getBatteryLevel');
      setState(() {
        batteryLevel = '$result%';
      });
    } on PlatformException catch (e) {
      setState(() {
        batteryLevel = "Failed to get battery level: '${e.message}'.";
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Battery Level')),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text('Battery Level: $batteryLevel'),
            ElevatedButton(
              child: Text('Get Battery Level'),
              onPressed: getBatteryLevel,
            ),
          ],
        ),
      ),
    );
  }
}