问题
Suppose I am currently on the page which has the URL /user/:id . Now from this page I navigate to next page :id/posts.
Now Is there a way, so that i can check what is the previous URL, i.e. /user/:id.
Below are my routes
export const routes: Routes = [
{
path: 'user/:id', component: UserProfileComponent
},
{
path: ':id/posts', component: UserPostsComponet
}
];
回答1:
You can subscribe to route changes and store the current event so you can use it when the next happens
previousUrl: string;
constructor(router: Router) {
router.events
.filter(event => event instanceof NavigationEnd)
.subscribe(e => {
console.log('prev:', this.previousUrl);
this.previousUrl = e.url;
});
}
See also How to detect a route change in Angular 2?
回答2:
Maybe all other answers are for angular 2.X.
Now it doesn't work for angular 5.X. I'm working with it.
with only NavigationEnd, you can not get previous url.
because Router works from "NavigationStart", "RoutesRecognized",..., to "NavigationEnd".
You can check with
router.events.forEach((event) => {
console.log(event);
});
But still you can not get previous url even with "NavigationStart".
Now you need to use pairwise.
import 'rxjs/add/operator/filter';
import 'rxjs/add/operator/pairwise';
constructor(private router: Router) {
this.router.events
.filter(e => e instanceof RoutesRecognized)
.pairwise()
.subscribe((event: any[]) => {
console.log(event[0].urlAfterRedirects);
});
}
With pairwise, You can see what url is from and to.
"RoutesRecognized" is the changing step from origin to target url.
so filter it and get previous url from it.
Last but not least,
put this code in parent component or higher (ex, app.component.ts)
because this code fires after finish routing.
Update angular 6+
The events.filter gives error because filter is not part of events, so change the code to
import { filter, pairwise } from 'rxjs/operators';
this.router.events
.pipe(filter((evt: any) => evt instanceof RoutesRecognized), pairwise())
.subscribe((events: RoutesRecognized[]) => {
console.log('previous url', events[0].urlAfterRedirects);
console.log('current url', events[1].urlAfterRedirects);
});
回答3:
Create a injectable service:
import { Injectable } from '@angular/core';
import { Router, RouterEvent, NavigationEnd } from '@angular/router';
/** A router wrapper, adding extra functions. */
@Injectable()
export class RouterExtService {
private previousUrl: string = undefined;
private currentUrl: string = undefined;
constructor(private router : Router) {
this.currentUrl = this.router.url;
router.events.subscribe(event => {
if (event instanceof NavigationEnd) {
this.previousUrl = this.currentUrl;
this.currentUrl = event.url;
};
});
}
public getPreviousUrl(){
return this.previousUrl;
}
}
Then use it everywhere you need. To store the current variable as soon as possible, it's necessary to use the service in the AppModule.
// AppModule
export class AppModule {
constructor(private routerExtService: RouterExtService){}
//...
}
// Using in SomeComponent
export class SomeComponent implements OnInit {
constructor(private routerExtService: RouterExtService, private location: Location) { }
public back(): void {
this.location.back();
}
//Strange name, but it makes sense. Behind the scenes, we are pushing to history the previous url
public goToPrevious(): void {
let previous = this.routerExtService.getPreviousUrl();
if(previous)
this.routerExtService.router.navigateByUrl(previous);
}
//...
}
回答4:
Angular 6 updated code for getting previous url as string.
import { Router, RoutesRecognized } from '@angular/router';
import { filter, pairwise } from 'rxjs/operators';
export class AppComponent implements OnInit {
constructor (
public router: Router
) {
}
ngOnInit() {
this.router.events
.pipe(filter((e: any) => e instanceof RoutesRecognized),
pairwise()
).subscribe((e: any) => {
console.log(e[0].urlAfterRedirects); // previous url
});
}
回答5:
This worked for me in angular 6 & 7:
this.router.events
.subscribe((event) => {
if (event instanceof NavigationStart) {
window.localStorage.setItem('previousUrl', this.router.url);
}
});
回答6:
@GünterZöchbauer also you can save it in localstorage but I not prefer it ) better to save in service and get this value from there
constructor(
private router: Router
) {
this.router.events
.subscribe((event) => {
if (event instanceof NavigationEnd) {
localStorage.setItem('previousUrl', event.url);
}
});
}
回答7:
I'm using Angular 8 and the answer of @franklin-pious solves the problem. In my case, get the previous url inside a subscribe cause some side effects if it's attached with some data in the view.
The workaround I used was to send the previous url as an optional parameter in the route navigation.
this.router.navigate(['/my-previous-route', {previousUrl: 'my-current-route'}])
And to get this value in the component:
this.route.snapshot.paramMap.get('previousUrl')
this.router and this.route are injected inside the constructor of each component and are imported as @angular/router members.
import { Router, ActivatedRoute } from '@angular/router';
回答8:
You can use Location as mentioned here.
Here's my code if the link opened on new tab
navBack() {
let cur_path = this.location.path();
this.location.back();
if (cur_path === this.location.path())
this.router.navigate(['/default-route']);
}
Required imports
import { Router } from '@angular/router';
import { Location } from '@angular/common';
回答9:
Angular 8 & rxjs 6 in 2019 version
I would like to share the solution based on others great solutions.
First make a service to listen for routes changes and save the last previous route in a Behavior Subject, then provide this service in the main app.component in constructor then use this service to get the previous route you want when ever you want.
use case: you want to redirect the user to an advertise page then auto redirect him/her to where he did came from so you need the last previous route to do so.
// service : route-events.service.ts
import { Injectable } from '@angular/core';
import { Router, RoutesRecognized } from '@angular/router';
import { BehaviorSubject } from 'rxjs';
import { filter, pairwise } from 'rxjs/operators';
import { Location } from '@angular/common';
@Injectable()
export class RouteEventsService {
// save the previous route
public previousRoutePath = new BehaviorSubject<string>('');
constructor(
private router: Router,
private locatoin: Location
) {
// ..initial prvious route will be the current path for now
this.previousRoutePath.next(this.locatoin.path());
// on every route change take the two events of two routes changed(using pairwise)
// and save the old one in a behavious subject to access it in another component
// we can use if another component like intro-advertise need the previous route
// because he need to redirect the user to where he did came from.
this.router.events.pipe(
filter(e => e instanceof RoutesRecognized),
pairwise(),
)
.subscribe((event: any[]) => {
this.previousRoutePath.next(event[0].urlAfterRedirects);
});
}
}
provide the service in app.module
providers: [
....
RouteEventsService,
....
]
Inject it in app.component
constructor(
private routeEventsService: RouteEventsService
)
finally use the saved previous route in the component you want
onSkipHandler(){
// navigate the user to where he did came from
this.router.navigate([this.routeEventsService.previousRoutePath.value]);
}
回答10:
I had similar problem when I had wanted to back to previous page. Solution was easier than I could imagine.
<button [routerLink]="['../']">
Back
</button>
And it returns to parent url. I hope it will help someone ;)
来源：https://stackoverflow.com/questions/41038970/how-to-determine-previous-page-url-in-angular