Flutter module in Android app

I am trying to put Flutter app as a module in Android app, I have followed this tutorial.

I am new with Flutter, and beginner with Android so probably missing some basics here.

I am stuck at these lines of code
flutterButton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {

The bolded part of the code is showing errors.

  1. I see others have put (this) or some other variable instead of currentActivity but it doesn’t help.
  2. The “OnClickListener” problem can be solved by adding import, it changes then to “View.OnClickListener”. Since 1 is still red I cant determine if this is good or bad.

My route in the Flutter module is initialRoute: AppPages.INITIAL