How to handle back button on Ionic 2

问题:

How can I handle the back button action on Ionic 2?

I want to be able to know what to do depending on which page is being shown to the user.

I didn't find a good answer to this question, but after a while I figured it out myself a way to do it. I'm gonna share with you all.

Thanks

回答1:

Here's how I did it:

In every Page component, I created a function called backButtonAction(), which will execute custom code for every page.

Code:

import { Component } from '@angular/core';
import { Platform, NavController, ModalController } from 'ionic-angular';
import { DetailsModal } from './details';

@Component({
    selector: 'page-appointments',
    templateUrl: 'appointments.html'
})
export class AppointmentsPage {
    modal: any;

    constructor(private modalCtrl: ModalController, public navCtrl: NavController, public platform: Platform) {
        // initialize your page here
    }

    backButtonAction(){
        /* checks if modal is open */
        if(this.modal && this.modal.index === 0) {
            /* closes modal */
            this.modal.dismiss();
        } else {
            /* exits the app, since this is the main/first tab */
            this.platform.exitApp();
            // this.navCtrl.setRoot(AnotherPage);  <-- if you wanted to go to another page
        }
    }

    openDetails(appointment){
        this.modal = this.modalCtrl.create(DetailsModal, {appointment: appointment});
        this.modal.present();
    }
}

And in the app.component.ts, I used the platform.registerBackButtonAction method to register a callback that will be called everytime the back button is clicked. Inside it I check if the function backButtonAction exists in the current page and call it, if it doesn't exists, just go to the main/first tab.

One could simplify this if they didn't need to perform customized actions for every page. You could just pop or exit the app.

I did it this way because I needed to check if the modal was open on this particular page.

Code:

  platform.registerBackButtonAction(() => {
    let nav = app.getActiveNav();
    let activeView: ViewController = nav.getActive();

    if(activeView != null){
      if(nav.canGoBack()) {
        nav.pop();
      }else if (typeof activeView.instance.backButtonAction === 'function')
        activeView.instance.backButtonAction();
      else nav.parent.select(0); // goes to the first tab
    }
  });

if the current page is the first tab, the app closes (as defined in the backButtonAction method).

回答2:

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({});
    }
  });

});

}

回答3:

I used answers from here and other sources to accomplish what I needed. I noticed that when you build the application for production (--prod) this approach doesn't work, because of JS uglifying and simplifying:

this.nav.getActive().name == 'PageOne'

Because of that, I use next in the "if" statement:

view.instance instanceof PageOne

So the final code looks like this:

this.platform.ready().then(() => {

  //Back button handling
  var lastTimeBackPress = 0;
  var timePeriodToExit = 2000;
  this.platform.registerBackButtonAction(() => {
    // get current active page
    let view = this.nav.getActive();
    if (view.instance instanceof PageOne) {
      if (new Date().getTime() - lastTimeBackPress < timePeriodToExit) {
          this.platform.exitApp(); //Exit from app
      } else {
        let toast = this.toastCtrl.create({
          message: 'Tap Back again to close the application.',
          duration: 2000,
          position: 'bottom',
        });
        toast.present();     
        lastTimeBackPress = new Date().getTime();
      } 
    } else if (view.instance instanceof PageTwo || view.instance instanceof PageThree) {
      this.openPage(this.pages[0]);
    } else {
      this.nav.pop({}); // go to previous page
    }
  });
});

回答4:

As per Ionic 2 RC.4 documentation from here:

You can use registerBackButtonAction(callback, priority) method of Platform API to register the action on back button press.

The back button event is triggered when the user presses the native platform’s back button, also referred to as the “hardware” back button. This event is only used within Cordova apps running on Android and Windows platforms. This event is not fired on iOS since iOS doesn’t come with a hardware back button in the same sense an Android or Windows device does.

Registering a hardware back button action and setting a priority allows apps to control which action should be called when the hardware back button is pressed. This method decides which of the registered back button actions has the highest priority and should be called.

Parameters :

• callback : Function to be called when the back button is pressed, if this registered action has the highest priority.
• priority : Number to set the priority for this action. Only the highest priority will execute. Defaults to 0

Returns: Function : A function that, when called, will un-register the back button action.

回答5:

Actually ionViewWillLeave works better in my case.

Here are the official docs about navigating lifecycle

回答6:

I was able to accomplish this in the event that we are simply setting root pages...

import {Component, ViewChild, Injector} from '@angular/core';
import {Platform, MenuController, Nav, App, IonicApp, NavController} from 'ionic-angular';
import {StatusBar} from '@ionic-native/status-bar';
import {SplashScreen} from '@ionic-native/splash-screen';
import {InvitesPage} from "../pages/invites/invites";
import {RewardsPage} from "../pages/rewards/rewards";
import {ConnectionsPage} from "../pages/connections/connections";
import {MessagesPage} from "../pages/messages/messages";
import {ResourcesPage} from "../pages/resources/resources";
import {SignoutPage} from "../pages/signout/signout";
import {DashboardPage} from "../pages/dashboard/dashboard";
import {AccountPage} from "../pages/account/account";
import {HomePage} from "../pages/home/home";
import {TriviaPage} from "../pages/trivia/trivia";
import {Events} from "ionic-angular/util/events";


@Component({
  templateUrl: 'app.html'
})
export class MyApp {
  @ViewChild(Nav) nav: NavController;
  // make HelloIonicPage the root (or first) page

  public rootPage: any; //if logged in, go to dashboard.
  public pages: Array<{title: string, component: any}>;
  public user: any;
  public routeHistory: Array<any>;

  constructor(public platform: Platform,
              public menu: MenuController,
              public statusBar: StatusBar,
              public splashScreen: SplashScreen,
              private _app: App,
              private _ionicApp: IonicApp,
              private _menu: MenuController,
              protected injector: Injector,
              public _events: Events) {

    this.initializeApp();

    // set our app's pages
    this.pages = [
      {title: 'My Account', component: AccountPage},
      {title: 'Dashboard', component: DashboardPage},
      {title: 'Invites', component: InvitesPage},
      {title: 'Rewards', component: RewardsPage},
      {title: 'Connections', component: ConnectionsPage},
      {title: 'Messages', component: MessagesPage},
      {title: 'Resources', component: ResourcesPage},
      {title: 'Trivia', component: TriviaPage},
      {title: 'Sign Out', component: SignoutPage}

    ];

    this.routeHistory = [];
    this.user = {firstName: ''};

  }

  initializeApp() {

    this.platform.ready().then(() => {

      this._setupBrowserBackButtonBehavior();

      let self = this;
      if (sessionStorage.getItem('user')) {
        this.user = JSON.parse(sessionStorage.getItem('user'));
        self.rootPage = TriviaPage;
      } else {
        self.rootPage = HomePage;
      }

      this.routeHistory.push(self.rootPage);
      // Okay, so the platform is ready and our plugins are available.
      // Here you can do any higher level native things you might need.
      this.statusBar.styleDefault();
      this.splashScreen.hide();
    });
  }

  openPage(page) {
    // close the menu when clicking a link from the menu
    this.menu.close();
    // navigate to the new page if it is not the current page
    this.nav.setRoot(page.component);
    //store route history
    this.routeHistory.push(page.component);
  }


  private _setupBrowserBackButtonBehavior() {

    // Register browser back button action(s)
    window.onpopstate = (evt) => {

      // Close menu if open
      if (this._menu.isOpen()) {
        this._menu.close();
        return;
      }

      // Close any active modals or overlays
      let activePortal = this._ionicApp._loadingPortal.getActive() ||
        this._ionicApp._modalPortal.getActive() ||
        this._ionicApp._toastPortal.getActive() ||
        this._ionicApp._overlayPortal.getActive();

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

      if (this.routeHistory.length > 1) {
        this.routeHistory.pop();
        this.nav.setRoot(this.routeHistory[this.routeHistory.length - 1]);
      }


    };

    // Fake browser history on each view enter
    this._app.viewDidEnter.subscribe((app) => {
      if (this.routeHistory.length > 1) {
        history.pushState(null, null, "");
      }

    });

  }
}

回答7:

I found the Easiest way, just add the following code in app.component:

this.platform.registerBackButtonAction((event) => {
    let activePortal = this.ionicApp._loadingPortal.getActive() ||
    this.ionicApp._modalPortal.getActive() ||
    this.ionicApp._toastPortal.getActive() ||
    this.ionicApp._overlayPortal.getActive();
    if(activePortal && activePortal.index === 0) {
        /* closes modal */
        activePortal.dismiss();
    } else {
        if(this.nav.getActive().name == 'Homepage') {    // your homepage
            this.platform.exitApp();
        }
        else {
            if(this.nav.canGoBack())
                this.nav.pop();
            this.nav.setRoot(Homepage);
        }
    }
},101);

That's it! No need to add extra code on every page!

回答8:

Best practice solution after long search .

it works 100%, and tested it in real device

   this.Platform.registerBackButtonAction(() => {
          // try to dismiss any popup or modal
          console.log("Back button action called");

          let activePortal = this.ionicApp._loadingPortal.getActive() ||
            this.ionicApp._modalPortal.getActive() ||
            this.ionicApp._toastPortal.getActive() ||
            this.ionicApp._overlayPortal.getActive();

          if (activePortal) {
            // ready = false;
            activePortal.dismiss();
            activePortal.onDidDismiss(() => {  });

            console.log("handled with portal");
            return;
          }

          // try to close the menue

          if(this.MenuController.isOpen()){
            this.closeMenu();
            return;
          }
          else if(this.nav.canGoBack()){
            this.nav.pop();
            return;
          }else{

            let activePage = this.nav.getActive().instance;

            let whitelistPages = [LoginPage, HomePage];

            // if current page is not in whitelistPage
            // then back to home or login page first
            if (whitelistPages.indexOf(activePage.constructor) < 0) {
              this.nav.setRoot(this.userLoggedIn ? HomePage : LoginPage);

              return;
            }else if(whitelistPages.indexOf(activePage.constructor) > 0){
              this.AppUtilities.showConfirm("Exit","Are you want to exist the app ? ").subscribe(
                ()=>{
                  this.Platform.exitApp();
                },
                ()=>{}
              )
            }else{
              console.error('cannot handel back button')
            }


          }

        });

回答9:

I have a slight different approach compare with @amr abdulaziz. Im using the setTimeout to control back or exit. Hope this would give another option for implement the back button.

  initBackButtonBehaviour() {
    this.platform.registerBackButtonAction(() => {
      console.log("Back button pressed");
      if (this.readyToExit) {
        this.platform.exitApp();
        return;
      }

      let activePortal = this.ionicApp._loadingPortal.getActive() ||
        this.ionicApp._modalPortal.getActive() ||
        this.ionicApp._toastPortal.getActive() ||
        this.ionicApp._overlayPortal.getActive();

      if (activePortal) {
        activePortal.dismiss();
        activePortal.onDidDismiss(() => { });

        return; // stop any further action after closing any pop up modal or overlay
      }

      if (this.menuCtrl.isOpen()) {
        this.menuCtrl.close();
        return;   // stop any further action after menu closed
      }
      else if (this.nav.canGoBack()) {
        this.nav.pop();
        return;   // stop any further action after navigation pop
      }
      else {
        let activePage = this.nav.getActive().instance;

        let whiteListPages = [HomePage];

        // if current page is not in whitelistPage
        // then back to home or login page first
        if (whiteListPages.indexOf(activePage.constructor) < 0) {
          this.nav.setRoot(HomePage);

          return;
        } else if (whiteListPages.indexOf(activePage.constructor) >= 0) {
          this.utils.showToast('Press back button again to exit', 1500);

          this.readyToExit = true;
          setTimeout(() => {
            this.readyToExit = false;
          }, 1500);

        } else {
          console.error('cannot handle back button');
        }

      }
    }, 101);

回答10:

I have Researched Many Things for back button handle Finally I Found a Good Solution for ionic latest Version 3.xx

//Check Hardware Back Button Double Tap to Exit And Close Modal On Hardware Back
      let lastTimeBackPress = 0;
      let timePeriodToExit  = 2000;
      this.platform.registerBackButtonAction(() => {
          let activePortal = this.ionicApp._loadingPortal.getActive() || // Close If Any Loader Active
          this.ionicApp._modalPortal.getActive() ||  // Close If Any Modal Active
          this.ionicApp._overlayPortal.getActive(); // Close If Any Overlay Active
          if (activePortal) {
              activePortal.dismiss();
          }
          else if(this.nav.canGoBack()){
            this.nav.pop();
          }else{
              //Double check to exit app
              if (new Date().getTime() - lastTimeBackPress < timePeriodToExit) {
                  this.platform.exitApp(); //Exit from app
              } else {
                this.toast.create("Press back button again to exit");
                lastTimeBackPress = new Date().getTime();
              }
          }            
      });

回答11:

In Ionic 3 Lazy Loading, I never felt the need of Handling back behavior of browser where as for platform.is('cordova') I have created following method which handles all back scenarios:

// If a view controller is loaded. Just dismiss it.
let nav = this.app.getActiveNav();
let activePortal = this._ionicApp._loadingPortal.getActive() ||
this._ionicApp._modalPortal.getActive() ||
this._ionicApp._toastPortal.getActive() ||
this._ionicApp._overlayPortal.getActive();
if(activePortal && activePortal.index === 0) {
    /* closes modal */
    activePortal.dismiss();
    return;
}

// If a state is pushed: Pop it.
if (this.nav.canGoBack()) {
  this.nav.pop();
  return;
} else 
// Else If its a tabs page: 
if (this.nav.getActiveChildNav()) {     
    const tabs: Tabs = this.nav.getActiveChildNav();
    const currentTab = tabs.getActiveChildNavs()[0];
    // If any page is pushed inside the current tab: Pop it
    if(currentTab.canGoBack()) {
      currentTab.pop();
      return;
    }
    else 
    // If home tab is not selected then select it.
    if(tabs.getIndex(currentTab) !=0){
      tabs.select(0);
      return;
    }
}
else 
// If a menu is open: close it.
if (this.menu.isOpen()) {
  this.menu.close();
  return;
}




if (this.exitApp) {
  this.platform.exitApp();
  return;
}
this.exitApp = true;

const toast = this.toastCtrl.create({
  message: this.exitMessage || 'press again to exit',
  duration: 4000,
  position: 'bottom',
  cssClass: 'exit-toastr',
});
toast.present();
setTimeout(() => {
  this.exitApp = false;
}, 2000);

回答12:

you can try this functions :

registerBackButton() {
        this.platform.registerBackButtonAction(() => {
            if (this.menu.isOpen()) {
                console.log("Menu is open!", "loggedInMenu");
                this.menu.close();
                console.log("this.menu.isOpen(): " + JSON.stringify(this.menu.isOpen()));
                return;
            }
            console.log("Checking for other pages");

            let checkHomePage = true;
            let max = Globals.navCtrls.length;
            for (let i = 0; i < Globals.navCtrls.length; i++) {
                let n = Globals.navCtrls[i];
                if (n) {
                    if (n.canGoBack()) {
                        console.log("Breaking the loop i: " + JSON.stringify(i));
                        let navParams = n.getActive().getNavParams();
                        if (navParams) {
                            console.log("navParams exists");
                            let resolve = navParams.get("resolve");
                            if (resolve) {
                                n.pop().then(() => resolve({}));
                            } else {
                                n.pop();
                            }
                        } else {
                            n.pop();
                        }
                        checkHomePage = false;
                        return;
                    }
                } else console.log("n was null!");
            }

            if (this.nav.getActive().instance instanceof TabsPage && !this.nav.canGoBack()) {
                let popPageVal = this.backbuttonService.popPage();
                console.log("popPageVal: " + JSON.stringify(popPageVal));
                if (popPageVal >= 0) {
                    console.log("Switching the tab to: ", popPageVal);
                    this.switchTab(popPageVal);
                } else {
                    console.log("Last page is HomePage");

                    if (this.alert) {
                        this.alert.dismiss();
                        this.alert = null;
                    } else {
                        this.showAlert();
                    }
                }
            } else {
                console.log("Last page is not HomePage");
                if (this.nav.canGoBack()) {
                    console.log("We can go back!");
                    this.nav.pop();
                }
            }
        });
    }

    showAlert() {
        this.alert = this.alertController.create({
            title: "Exit?",
            message: "Are you sure you want to exit?",
            buttons: [
                {
                    text: "Cancel",
                    role: "cancel",
                    handler: () => {
                        this.alert = null;
                    }
                },
                {
                    text: "Exit",
                    handler: () => {
                        this.platform.exitApp();
                    }
                }
            ]
        });
        this.alert.present();
    }

    switchTab(tabIndex) {
        if (Globals.tabs && tabIndex >= 0) {
            console.log("Switch condition met");
            Globals.tabIndex = tabIndex;
            Globals.tabs.select(tabIndex);
            Globals.tabs.selectedIndex = tabIndex;
        }
    }

I hope its works with you.