要在Angular 7中接收Firebase通知，您可以使用Firebase Cloud Messaging（FCM）库。以下是一个解决方法的示例代码：

1. 安装Firebase和FCM库：

npm install firebase @angular/fire

2. 在Angular应用程序中导入Firebase和FCM模块：

import { AngularFireModule } from '@angular/fire';
import { AngularFireMessagingModule } from '@angular/fire/messaging';

@NgModule({
  declarations: [
    // ...
  ],
  imports: [
    // ...
    AngularFireModule.initializeApp(environment.firebaseConfig),
    AngularFireMessagingModule,
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

3. 创建一个MessagingService来处理Firebase通知的接收：

import { Injectable } from '@angular/core';
import { AngularFireMessaging } from '@angular/fire/messaging';
import { BehaviorSubject } from 'rxjs';

@Injectable()
export class MessagingService {
  currentMessage = new BehaviorSubject(null);

  constructor(private angularFireMessaging: AngularFireMessaging) {
    this.angularFireMessaging.messages.subscribe(
      (message) => {
        console.log('Received message:', message);
        this.currentMessage.next(message);
      }
    );
  }
}

4. 在组件中使用MessagingService来接收Firebase通知：

import { Component } from '@angular/core';
import { MessagingService } from './messaging.service';

@Component({
  selector: 'app-root',
  template: `
    
Received Message:
    
{{ message | async | json }}
  `,
})
export class AppComponent {
  message;

  constructor(private messagingService: MessagingService) {
    this.message = messagingService.currentMessage;
  }
}

这样，您的Angular 7应用程序就可以接收和处理来自Firebase的通知了。