Exit ionic 4 app on pressing back button.

example.text

  import { fromEvent } from "rxjs";           // import fromEvent from rxjs
  import { Router } from "@angular/router";   // import angular router as well
  import { Location } from "@angular/common"; // import location from angular common,
  
  // Inject Router and Location
  constructor(private router: Router, private location: Location,) {
  // Call the funtion when the app initializes at app.component.ts. it will watch for backbutton events globally in
  // the application
    this.backButtonEvent();
  } 
  
  // Function to present the exit alert
   async exitAlert() {
    const alert = await this.alertController.create({
      // header: 'Confirm!',
      message: "Are you sure you want to exit the app?",
      buttons: [
        {
          text: "Cancel",
          role: "cancel",
          cssClass: "secondary",
          handler: blah => {}
        },
        {
          text: "Close App",
          handler: () => {
            navigator["app"].exitApp();
          }
        }
      ]
    });

    await alert.present();
  }
  
   // write function to subscribe to the backbutton event
  backButtonEvent(): void {
    const event = fromEvent(document, "backbutton");
    event.subscribe(async () => {
    // When the current route matches a specific page in the app where u want this function to work.
    // else it assumes the user wants to navigate to a previous page
     if(this.router.url === "<example page-url to exit from>") { this.exitAlert() }
     else { this.location.back() } 
    });
  }

I found this extremely useful. Shocked not to see any comments or stars and many devs have this problem with exiting ionic apps. Thanks a whole lot!

I found this extremely useful. Shocked not to see any comments or stars and many devs have this problem with exiting ionic apps. Thanks a whole lot!

Thank you, I'm really glad it was useful to you :)