cdchild.js

import { Component, OnInit, Input, ChangeDetectionStrategy, OnChanges, ChangeDetectorRef } from '@angular/core';
import { Observable } from 'rxjs';
import { TouchSequence } from 'selenium-webdriver';

@Component({
  selector: 'app-child',
  template: `
     <h2>Items : {{_data.counter}} </h2>
    <button (click)='0'>Refresh</button>
  `,
  changeDetection:ChangeDetectionStrategy.OnPush
})
export class AppChildComponent implements OnInit , OnChanges {
 _data ; 
  @Input() data :  Observable<any> ; 
  @Input() notifier : Observable<boolean>;
  constructor(private cd : ChangeDetectorRef) { }

  ngOnInit() {
    this.data.subscribe(value=>{
     
     
      this._data = value;
      this.cd.markForCheck();
    });
    this.cd.detach();
    this.notifier.subscribe(value=>{
      if(value){
        this.cd.reattach();
      }
      else{
        this.cd.detach();
      }
    })
  }
  ngOnChanges(){
    console.log(this.data);
  }

}

cdparent.js

import { Component, OnInit, ChangeDetectionStrategy, ChangeDetectorRef } from '@angular/core';
import { BehaviorSubject } from 'rxjs';


@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {

  _counter = 0; 
  data: any;
  _interval; 
  t = false; 
  notifier = new BehaviorSubject(false);
  start(){
    if(!this._interval){
      this._interval = setInterval(()=>{
        this.data.next({
  
          counter: ++this._counter
        })
      },10 )
  }
}

stop(){
  clearInterval(this._interval);
  this._interval = null; 
}

toggle(){
  this.t = !this.t;
  this.notifier.next(this.t);
}

  constructor() {


  }

  increment(){
   // this.data.counter++; 
  // this.data = { counter: ++this.data.counter + 10};

  }

  ngOnInit() {
        // this.data = {
    //   counter: 0
    // }

    this.data = new BehaviorSubject({
      counter: 0
    })
  }


}

cdparent1.html

<button (click)='start()'>Start</button>
<button (click)='stop()'>Stop</button>
<button (click)='toggle()'>Toggle Change Detection</button>
<hr />

<app-child [notifier]='notifier' [data]='data'></app-child>