How to update content on another activity

I have a native map view on the second activity. I would like to update the position of the dot from Flutter in the background. How can I get to access the activity so I can update the position?

I am new to Android Native. Thank you.

MainActivity.kt:

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    GeneratedPluginRegister.registerGeneratedPlugins(FlutterEngine(this@MainActivity))
    MethodChannel(flutterEngine?.dartExecutor!!, CHANNEL).setMethodCallHandler { call, result ->
        if(call.method.equals("goToSecondActivity")){
            goToSecondActivity()
        } else if(call.method.equals("updatePosition")) {
            val lat = call.argument<Double>("lat")
            val long = call.argument<Double>("long")
            val accuracy = call.argument<Double>("accuracy") ?: 7.170562529369844
            val floorLevel = call.argument<Int>("floor") ?: 0
            updatePosition(lat!!, long!!, accuracy, floorLevel)
        } else {
            result.notImplemented()
        }
    }
}


private fun goToSecondActivity() {
    startActivity(Intent(this@MainActivity, SecondActivity::class.java))
}