1. When you are going to jump with Navgation in ionic, you will find that there is no reference to ionic-angular, and then you will make a mistake if you refer to it yourself.
2, Environment:

    ionic --  4.5.0
    cordova --  8.1.2
    npm --  6.4.1

3. Create project command:

    ionic start myDemo01 tabs

create news interface:

    ionic g components/news page

Import Navigation into tab1.page.ts in tab1 and prepare to jump with Nav. Command:

    import { Page,NavController,NavParams } from "ionic-angular";

4, and then report an error after import

All imports in import declaration are unused.ts(6192)
Cannot find module "ionic-angular".ts(2307)