title: Unhandled Exception: MissingPluginException(No implementation found for method getBatteryLevel on channel *) with flutter1.12
body: <p>We have recently migrated to <code>flutter1.12</code> with which we thought to be using the Add2App feature but when started testing the method channel it always throws me an error saying </p>
  
  <blockquote>
    <p>Unhandled Exception: MissingPluginException(No implementation found
    for method getBatteryLevel on channel com.app.test/channel)</p>
  </blockquote>
  
  <p>I have tried to use the same code by creating a module still no luck. Could someone help me to understand the issue and get the resolution for the same.</p>
  
  <p>Here is what I have been trying</p>
  
  <p>my <strong>main.dart code</strong></p>
  
  <pre><code>    import 'package:flutter/material.dart';
      import 'package:flutter/services.dart';
  
      void main() =&gt; runApp(MyApp());
  
      class MyApp extends StatelessWidget {
      // This widget is the root of your application.
      @override
      Widget build(BuildContext context) {
       return MaterialApp(
        title: 'Flutter Demo',
        theme: ThemeData(
          // This is the theme of your application.
          //
          // Try running your application with "flutter run". You'll see the
          // application has a blue toolbar. Then, without quitting the app, try
          // changing the primarySwatch below to Colors.green and then invoke
          // "hot reload" (press "r" in the console where you ran "flutter run",
          // or press Run &gt; Flutter Hot Reload in a Flutter IDE). Notice that the
          // counter didn't reset back to zero; the application is not restarted.
          primarySwatch: Colors.blue,
        ),
        home: MyHomePage(title: 'Flutter Demo Home Page'),
      );
      }
     }
  
  class MyHomePage extends StatefulWidget {
    MyHomePage({Key key, this.title}) : super(key: key);
  
    // This widget is the home page of your application. It is stateful, meaning
    // that it has a State object (defined below) that contains fields that affect
    // how it looks.
  
    // This class is the configuration for the state. It holds the values (in this
    // case the title) provided by the parent (in this case the App widget) and
    // used by the build method of the State. Fields in a Widget subclass are
    // always marked "final".
  
    final String title;
  
    @override
    _MyHomePageState createState() =&gt; _MyHomePageState();
   }
  
  class _MyHomePageState extends State&lt;MyHomePage&gt; {
    static const platform = const MethodChannel("com.app.test/channel");
    int _counter = 0;
  
    String _batteryLevel = 'Unknown battery level.';
  
    Future&lt;void&gt; _getBatteryLevel() async {
      String batteryLevel;
      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;
      });
    }
    void _incrementCounter() {
  
      setState(() {
  
        // This call to setState tells the Flutter framework that something has
        // changed in this State, which causes it to rerun the build method below
        // so that the display can reflect the updated values. If we changed
        // _counter without calling setState(), then the build method would not be
        // called again, and so nothing would appear to happen.
        _counter++;
      });
    }
  
    @override
    Widget build(BuildContext context) {
      // This method is rerun every time setState is called, for instance as done
      // by the _incrementCounter method above.
      //
      // The Flutter framework has been optimized to make rerunning build methods
      // fast, so that you can just rebuild anything that needs updating rather
      // than having to individually change instances of widgets.
      return Scaffold(
        appBar: AppBar(
          // Here we take the value from the MyHomePage object that was created by
          // the App.build method, and use it to set our appbar title.
          title: Text(widget.title),
        ),
        body: Center(
          // Center is a layout widget. It takes a single child and positions it
          // in the middle of the parent.
          child: Column(
            // Column is also a layout widget. It takes a list of children and
            // arranges them vertically. By default, it sizes itself to fit its
            // children horizontally, and tries to be as tall as its parent.
            //
            // Invoke "debug painting" (press "p" in the console, choose the
            // "Toggle Debug Paint" action from the Flutter Inspector in Android
            // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
            // to see the wireframe for each widget.
            //
            // Column has various properties to control how it sizes itself and
            // how it positions its children. Here we use mainAxisAlignment to
            // center the children vertically; the main axis here is the vertical
            // axis because Columns are vertical (the cross axis would be
            // horizontal).
            mainAxisAlignment: MainAxisAlignment.center,
            children: &lt;Widget&gt;[
              Text(
                'You have pushed the button this many times:',
              ),
  
              Text(
                '$_counter',
                style: Theme.of(context).textTheme.display1,
              ),
              RaisedButton(
                child: Text('Get Battery Level'),
                onPressed: _getBatteryLevel,
              ),
              Text(_batteryLevel),
            ],
          ),
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: _incrementCounter,
          tooltip: 'Increment',
          child: Icon(Icons.add),
        ), // This trailing comma makes auto-formatting nicer for build methods.
      );
    }
  }
  </code></pre>
  
  <p>And here is my <strong>MainActivity.java</strong> where the actual method exist to get the batterylevel</p>
  
  <pre><code>import android.content.ContextWrapper;
  import android.content.Intent;
  import android.content.IntentFilter;
  import android.os.BatteryManager;
  import android.os.Build.VERSION;
  import android.os.Build.VERSION_CODES;
  import android.os.Bundle;
  
  import java.nio.ByteBuffer;
  
  import androidx.annotation.NonNull;
  import io.flutter.embedding.android.FlutterActivity;
  import io.flutter.embedding.engine.FlutterEngine;
  import io.flutter.plugin.common.BinaryMessenger;
  import io.flutter.plugin.common.MethodCall;
  import io.flutter.plugin.common.MethodChannel;
  import io.flutter.plugins.GeneratedPluginRegistrant;
  
  
  public class MainActivity extends FlutterActivity {
  
      @Override
      public void configureFlutterEngine(@NonNull FlutterEngine flutterEngine) {
          GeneratedPluginRegistrant.registerWith(flutterEngine);
      }
      private int getBatteryLevel() {
          int batteryLevel = -1;
          if (VERSION.SDK_INT &gt;= VERSION_CODES.LOLLIPOP) {
              BatteryManager batteryManager = (BatteryManager) getSystemService(BATTERY_SERVICE);
              batteryLevel = batteryManager.getIntProperty(BatteryManager.BATTERY_PROPERTY_CAPACITY);
          } else {
              Intent intent = new ContextWrapper(getApplicationContext()).
                      registerReceiver(null, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
              batteryLevel = (intent.getIntExtra(BatteryManager.EXTRA_LEVEL, -1) * 100) /
                      intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1);
          }
  
          return batteryLevel;
      }
  
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
  
  
          BinaryMessenger binaryMessenger = new BinaryMessenger() {
              @Override
              public void send(String channel, ByteBuffer message) {
              }
  
              @Override
              public void send(String channel, ByteBuffer message, BinaryReply callback) {
  
              }
  
              @Override
              public void setMessageHandler(String channel, BinaryMessageHandler handler) {
  
              }
          };
          new MethodChannel(binaryMessenger, "com.app.test/channel").setMethodCallHandler(
                  new MethodChannel.MethodCallHandler() {
                      @Override
                      public void onMethodCall(MethodCall call, MethodChannel.Result result) {
                          if (call.method.equals("getBatteryLevel")) {
                              int batteryLevel = getBatteryLevel();
  
                              if (batteryLevel != -1) {
                                  result.success(batteryLevel);
                              } else {
                                  result.error("UNAVAILABLE", "Battery level not available.", null);
                              }
                          } else {
                              result.notImplemented();
                          }
                      }
                  });
      }
  }
  </code></pre>
  
  <p>I have been breaking my head past 2 days to understand the issue because I have tried so many possible fixes like flutter clean and flutter pub cache repair and all the other options that I can.</p>