How to pass a message from Flutter to Native?

This is a simple implementation showcasing:

1. Passing a string Value from flutter to Android code
2. Getting back response from Android code to flutter

Code is based on example from: https://flutter.io/platform-channels/#codec

1. Passing string value “text”:

   String text = "whatever";
   
   Future<Null> _getBatteryLevel(text) async {
   String batteryLevel;
   try {
     final String result = await platform.invokeMethod('getBatteryLevel',{"text":text}); 
     batteryLevel="Battery level at $result % .";
   } on PlatformException catch (e) {
     batteryLevel = "Failed to get battery level: '${e.message}'.";
   }
   
   setState(() {
     _batteryLevel = batteryLevel;
   });   
   
   

2. Getting back response “batterylevel” after RandomFunction();

   public void onMethodCall(MethodCall call, MethodChannel.Result result) {
       if (call.method.equals("getBatteryLevel")) {
   
           text = call.argument("text");
           String batteryLevel = RandomFunction(text);
   
           if (batteryLevel != null) {
               result.success(batteryLevel);
           } else {
               result.error("UNAVAILABLE", "Battery level not available.", null);
           }
       } else {
           result.notImplemented();
       }
   }