Angular 在离开页面之前警告用户未保存的更改

为了涵盖针对浏览器刷新、关闭窗口等的防护(有关该问题的详细信息，请参阅@ChristopheVdal对Günter回答的 comments )，我发现在您的类的canDeactivate实现中添加@HostListener修饰符来监听beforeunload window事件会很有帮助.如果配置正确，这将同时防止应用内导航和外部导航.

例如:

Component:个

import { ComponentCanDeactivate } from './pending-changes.guard';
import { HostListener } from '@angular/core';
import { Observable } from 'rxjs/Observable';

export class MyComponent implements ComponentCanDeactivate {
  // @HostListener allows us to also guard against browser refresh, close, etc.
  @HostListener('window:beforeunload')
  canDeactivate(): Observable<boolean> | boolean {
    // insert logic to check if there are pending changes here;
    // returning true will navigate without confirmation
    // returning false will show a confirm dialog before navigating away
  }
}

Guard:

import { CanDeactivate } from '@angular/router';
import { Injectable } from '@angular/core';
import { Observable } from 'rxjs/Observable';

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

@Injectable()
export class PendingChangesGuard implements CanDeactivate<ComponentCanDeactivate> {
  canDeactivate(component: ComponentCanDeactivate): boolean | Observable<boolean> {
    // if there are no pending changes, just allow deactivation; else confirm first
    return component.canDeactivate() ?
      true :
      // NOTE: this warning message will only be shown when navigating elsewhere within your angular app;
      // when navigating away from your angular app, the browser will show a generic warning message
      // see http://stackoverflow.com/a/42207299/7307355
      confirm('WARNING: You have unsaved changes. Press Cancel to go back and save these changes, or OK to lose these changes.');
  }
}

Routes:

import { PendingChangesGuard } from './pending-changes.guard';
import { MyComponent } from './my.component';
import { Routes } from '@angular/router';

export const MY_ROUTES: Routes = [
  { path: '', component: MyComponent, canDeactivate: [PendingChangesGuard] },
];

Module:

import { PendingChangesGuard } from './pending-changes.guard';
import { NgModule } from '@angular/core';

@NgModule({
  // ...
  providers: [PendingChangesGuard],
  // ...
})
export class AppModule {}

NOTE:正如@JasperRissee uw指出的，IE和Edge处理beforeunload事件的方式与其他浏览器不同，当beforeunload事件激活时(例如，浏览器刷新、关闭窗口等)，IE和Edge将在确认对话框中包含单词false.在Angular 应用程序内导航不受影响，并将正确显示您指定的确认警告消息.那些需要支持IE/Edge并且不希望false在beforeunload事件激活时在确认对话框中显示/希望显示更详细消息的用户，也可能希望查看@JasperRissee uw的解决方法答案.