Ionic 4 / Angular 6-从app.component的生命周期挂钩中获取数据

Question

I have my navigation set up in my app.component.html , and I would like to use an *ngIf inside that template. However, since lifecycle hooks like ionViewWillEnter , etc don't work in app.component.ts , how can I trigger a call to fire every time the side nav is popped open?

I am just trying to get a red dot to show if there are notifications in my array

app.component.html

    ...
    <ion-list>
      <ion-menu-toggle auto-hide="false" *ngFor="let p of appPages">
        <ion-item [routerDirection]="'root'" [routerLink]="[p.url]">
          <ion-icon slot="start" [name]="p.icon"></ion-icon>
          =====>HERE===><div class="red-dot" *ngIf="p.title == 'Home' && notifications.length > 0"></div> 
          <ion-label>
            {{p.title}}
          </ion-label>
        </ion-item>
      </ion-menu-toggle>
    </ion-list>
  </ion-content>
</ion-menu>
<ion-router-outlet main></ion-router-outlet>
...

app.component.ts

...
initializeApp() {
const parseQueryString = (queryString) => {
  const query = <any>{};
  for (let param of queryString.split('&')) {
    const pair = param.split('=');
    query[pair[0]] = pair[1];
  }
  return query;
};

this.platform.ready().then(() => {
  this.statusBar.styleDefault();
  this.splashScreen.hide();
  this.deepLinks.route({
  ...

What I want to add to the side nav logic

const newData = await this.api.listModel('Notification', {
  page: this.page
});
this.notifications = this.notifications.concat(newData);
this.notifications = _.filter(this.notifications, { isActioned: false }

Answer 1

As far as I understood this is same component. You can try to call detectChanges() whenever notifications array is changed. More info here: https://angular.io/api/core/ChangeDetectorRef

If this is not same component, you can use service and Observables from Rxjs as proxies.