MainActivity.java for add2app scenario with 'custom' plugin internal to package and regular plugin

MainActivity.java

package com.example.fluttergetstringdriver;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.FrameLayout;


import io.flutter.app.FlutterPluginRegistry;
import io.flutter.facade.Flutter;
import io.flutter.plugins.GeneratedPluginRegistrant;
import io.flutter.view.FlutterView;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                FlutterView flutterView = Flutter.createView(MainActivity.this, getLifecycle(), "route1");

                FlutterPluginRegistry flutterPluginRegistry = flutterView.getPluginRegistry();
                GeneratedPluginRegistrant.registerWith(flutterPluginRegistry);

                //NOTE: This name should match canonical name of the plugin.
                GetStringPlugin.registerWith(flutterPluginRegistry.registrarFor("com.example.fluttergetstringdriver.GetStringPlugin"));

                FrameLayout.LayoutParams layout = new FrameLayout.LayoutParams(600, 800);
                layout.leftMargin = 10;
                layout.topMargin = 50;
                addContentView(flutterView, layout);
            }
        });
    }

}