Ionic 2: How to handle the hardware back button wh

Question

I am facing an issue how to handle the default mobile's back button which checks the confirmation while exiting from the application, if I pressed the back button there should invoke some handler which shows pop-up, for confirm exiting. OR there is any method call registerBackButtonAction()? or is it so how to use it in IONIC 2,? Please help me out. Thanks in Advance.

Answer 1

Platform api has a handler registerBackButtonAction.

You can do something like:

In app.component.ts

    constructor(platform: Platform){
     platform.ready().then(()=>{
       platform.registerBackButtonAction(()=>this.myHandlerFunction());
})


  myHandlerFunction(){
    //create alert
     }

Answer 2

Kinda late to the party... But there is more to back button other than closing the pushed pages, specially for project with several tab pages.

Sometimes a page is pushed NOT into the root page, but in one of the tab page's navCtrl. So we have to check for all of them.

Also, if no page or menu is open, we should circle around the most recently used tabs (similar to Instagram app) and go back to the previous tab. Moreover, we should not go back to each tab more than once (similar to Instagram)

I got inspired by the answers here and created a comprehensive method that handles all necessary features:

• Side menu: Closes the side menu if it was open
• Pushed pages: Closes any pages that might have been pushed on any of the tab pages’ nav controller
• Switch between tabs: If the menu was closed, and there was no pushed page, it should take the user back to the previous recently used tab using a stack.
• Show alert: If there was no previous recently used tab, an alert box should ask the user if they want to exit.

The details are in this blog post

A demo code can be downloaded from my github.

Answer 3

In app.component.ts

        @ViewChild(Nav) nav: Nav;

        constructor(private platform: Platform, private toastCtrl:   ToastController, private alertCtrl: AlertController) {
            platform.ready().then(() => {
              // Okay, so the platform is ready and our plugins are available.
              // Here you can do any higher level native things you might need

              platform.registerBackButtonAction(() => {


                //uncomment this and comment code below to to show toast and exit app
                // if (this.backButtonPressedOnceToExit) {
                //   this.platform.exitApp();
                // } else if (this.nav.canGoBack()) {
                //   this.nav.pop({});
                // } else {
                //   this.showToast();
                //   this.backButtonPressedOnceToExit = true;
                //   setTimeout(() => {

                //     this.backButtonPressedOnceToExit = false;
                //   },2000)
                // }

                if(this.nav.canGoBack()){
                  this.nav.pop();
                }else{
                  if(this.alert){ 
                    this.alert.dismiss();
                    this.alert =null;     
                  }else{
                    this.showAlert();
                   }
                }
              });
            });

          }

          showAlert() {
          this.alert = this.alertCtrl.create({
            title: 'Exit?',
            message: 'Do you want to exit the app?',
            buttons: [
              {
                text: 'Cancel',
                role: 'cancel',
                handler: () => {
                  this.alert =null;
                }
              },
              {
                text: 'Exit',
                handler: () => {
                  this.platform.exitApp();
                }
              }
            ]
          });
          alert.present();
        }

          showToast() {
            let toast = this.toastCtrl.create({
              message: 'Press Again to exit',
              duration: 2000,
              position: 'bottom'
            });

            toast.onDidDismiss(() => {
              console.log('Dismissed toast');
            });

            toast.present();
          }

Answer 4

Html:

<button (click)="exitApp()">Close application<button>

TypeScript:

import {Platform} from 'ionic-angular';

@Page({ /*...*/ })
export MyPage {
 constructor(platform: Platform) {
  this.platform = platform;
 }
 exitApp(){
  this.platform.exitApp();
 }
}

Answer 5

I managed to create this function by doing a lot of research. Hope it helps.

    // I am using this.isExitAlertOpen just to make sure that the alert does not open if already open.

    handleBackButton() {
    this.platform.registerBackButtonAction(() => {
        // const activePortal =
        // this.ionicApp._modalPortal.getActive() ||
        // this.ionicApp._loadingPortal.getActive() ||
        // this.ionicApp._toastPortal.getActive() ||
        // this.ionicApp._overlayPortal.getActive();

        // console.warn('ACTIVE PORTALS', activePortal);

        const activeModal = this.ionicApp._modalPortal.getActive();
        console.warn('MODAL', activeModal);

activePortal can be used to find the relevant active portals which includes alert, loader, modal, etc. If you want to handle everything with the back button or some of them uncomment according to your usage

In my case I only wanted to check if modal was active so I checked only for modal.

        //  if (activePortal) {
        //    activePortal.dismiss();
        //  }

        if (activeModal) {
            activeModal.dismiss();
        } else if (this.nav.canGoBack()) {
            this.nav.pop();
        } else {
            if (this.isExitAlertOpen) return;
            this.isExitAlertOpen = true;
            this.showExitAlert();
        }
    });
}

showExitAlert() {
    this.alertCtrl.create({
        title: 'Exit',
        message: 'Are you sure you want to exit the app?',
        enableBackdropDismiss: false,
        buttons: [
            {
                text: 'Yes',
                handler: () => {
                    this.isExitAlertOpen = false;
                    this.platform.exitApp();
                }
            }, {
                text: 'Cancel',
                role: 'cancel',
                handler: () => {
                    this.isExitAlertOpen = false;
                }
            }
        ]
    }).present();
}

Answer 6

Ionic latest version 3.xx

app.component.ts file:

import { Platform, Nav, Config, ToastController } from 'ionic-angular';

constructor(public toastCtrl: ToastController, public platform: Platform) {
    platform.ready().then(() => {
        //back button handle
        //Registration of push in Android and Windows Phone
        var lastTimeBackPress = 0;
        var timePeriodToExit  = 2000;

        platform.registerBackButtonAction(() => {
            // get current active page
            let view = this.nav.getActive();
            if (view.component.name == "TabsPage") {
                //Double check to exit app
                if (new Date().getTime() - lastTimeBackPress < timePeriodToExit) {
                    this.platform.exitApp(); //Exit from app
                } else {
                    let toast = this.toastCtrl.create({
                        message:  'Press back again to exit App?',
                        duration: 3000,
                        position: 'bottom'
                    });
                    toast.present();
                    lastTimeBackPress = new Date().getTime();
                }
            } else {
                // go to previous page
                this.nav.pop({});
            }
        });
    });
}