Android studio build error

[jw-redpanda]

I am new to capacitorjs. Trying out to build a custom plugin for an ionic angular app. The app can run on Android.

Then, I follow the instructions in https://capacitorjs.com/docs/v3/android/custom-code, added a new class EchoPlugin.java. When compile, it says

error: package com.getcapacitor.annotation does not exist
import com.getcapacitor.annotation.CapacitorPlugin;

I added a line to register EchoPlugin.class in MainActivity right after super.onCreate() but it says
Cannot resolve method 'registerPlugin' in 'MainActivity'

versions for your reference:
node/npm 14.16.0 / 6.14.11
ionic 6.13.1
angular 11.2.6
cap 2.4.7

I guess I missed some steps.

[jw-redpanda]

Try answer my question.
I didn't aware there is a small v2/v3 icon right next to the "capacitor doc". When I switch it to v2, and follow the code, it can compile and run.

Then, I follow the instructions in https://capacitorjs.com/docs/v3/android/custom-code, added a new class EchoPlugin.java. When compile, it says