angular - 如何在 Angular 4 中单击浏览器后退按钮时提醒用户？

Question

如何在 Angular 4 中单击浏览器后退按钮时提醒用户？

onpopstate 即使在页面第一次加载时也会被调用

import {  PlatformLocation } from '@angular/common';

    constructor( private platformLocation: PlatformLocation) {
        platformLocation.onPopState(() => {
          console.log("onPopState called");
          window.alert("your data will be lost");
        })
    }

Answer 1

添加一个candeactivate守卫

可以停用-guard.service.ts

import {Observable} from 'rxjs';
import {CanDeactivate, ActivatedRouteSnapshot, RouterStateSnapshot} from '@angular/router';

export interface CanComponentDeactivate {
  canDeactivate: () => Observable<boolean> | Promise<boolean> | boolean;
}

export class CanDeactivateGuard implements CanDeactivate<CanComponentDeactivate> {
  canDeactivate(component: CanComponentDeactivate, 
                currentRoute: ActivatedRouteSnapshot,
                currentState: RouterStateSnapshot,
                nextState?: RouterStateSnapshot
                ) : Observable<boolean> | Promise<boolean> | boolean {
    return component.canDeactivate();
  }
}

在您的路由设置中

const route: Route = [
  {path: '', component: AppComponent, canDeactivate: [CanDeactivateGuard]}
]

提供您可以在providers数组中的app.module中停用守卫。

考虑以下组件，其中我有变量来检查已保存的更改

export class AppComponent implements CanComponentDeactivate {
   changesSaved = false;
   onUpdateServer() {
     this.changesSaved = true;
   }
   canDeactivate() {
      if(this.changesSaved) {
        return true;
      } else {
        return confirm('Do you want to discard changes');
      }
   }
}