角材料表分页，排序和Firebase

Question

我非常努力地使该表与分页和排序以及Firebase一起使用。我能够使该表与firebase一起使用，但是当我尝试引入排序和分页时，一切开始变得模糊。我阅读了文档，然后看到了原理图，所以我生成了材料表的原理图，并尝试对其进行修改，但这只是在这里。不知道为什么这似乎比需要的挑战更多。我已经在这里呆了几天了，我在这里想念什么？

这是我的Data-table-datasource.ts

import { DataSource } from '@angular/cdk/collections';
import { MatPaginator, MatSort } from '@angular/material';
import { map } from 'rxjs/operators';
import { Observable, of as observableOf, merge } from 'rxjs';
import { DataviewdataService } from 'src/app/dataviewdata.service';
import { Inject, Injectable } from '@angular/core';
import { AngularFireDatabase, AngularFireList } from '@angular/fire/database';
import { FirebaseApp } from '@angular/fire'

// TODO: Replace this with your own data model type
export interface DataTableItem {
  name: string;
  id: number;
  time: string;
}

@Injectable()
export class DataviewdataService {

  private alertData$: AngularFireList<any[]>;

  constructor(
    public db: AngularFireDatabase, 
    private alert: DataviewdataService,




    @Inject(FirebaseApp) fb) {
      this.alertData$ = db.list('alerts');
    }



export class DataTableDataSource extends DataSource<DataTableItem> {
  data: DataTableItem[] = this.alert = db.list('alerts').valueChanges();


  constructor(private paginator: MatPaginator, private sort: MatSort) {
    super();
  }


  connect(): Observable<DataTableItem[]> {

    const dataMutations = [
      observableOf(this.data),
      this.paginator.page,
      this.sort.sortChange
    ];


    this.paginator.length = this.data.length;

    return merge(...dataMutations).pipe(map(() => {
      return this.getPagedData(this.getSortedData([...this.data]));
    }));
  }


  disconnect() {}


  private getPagedData(data: DataTableItem[]) {
    const startIndex = this.paginator.pageIndex * this.paginator.pageSize;
    return data.splice(startIndex, this.paginator.pageSize);
  }


  private getSortedData(data: DataTableItem[]) {
    if (!this.sort.active || this.sort.direction === '') {
      return data;
    }

    return data.sort((a, b) => {
      const isAsc = this.sort.direction === 'asc';
      switch (this.sort.active) {
        case 'name': return compare(a.name, b.name, isAsc);
        case 'id': return compare(+a.id, +b.id, isAsc);
        default: return 0;
      }
    });
  }
}


function compare(a, b, isAsc) {
  return (a < b ? -1 : 1) * (isAsc ? 1 : -1);
}

我的dataviewdata.service从Firebase获取数据：

import { Injectable } from '@angular/core';

import { AngularFireDatabase } from '@angular/fire/database';



@Injectable({
  providedIn: 'root'
})
export class DataviewdataService {

  constructor(private db: AngularFireDatabase) { }

  getAlerts(){
    return this.db.list('alerts').valueChanges();
  }
}

我的data-table.component.ts：

import { Component, OnInit, ViewChild, ElementRef} from '@angular/core';
import { MatPaginator, MatSort } from '@angular/material';
import { DataTableDataSource } from './data-table-datasource';
import * as XLSX from 'xlsx';

@Component({
  selector: 'data-table',
  templateUrl: './data-table.component.html',
  styleUrls: ['./data-table.component.css']
})
export class DataTableComponent implements OnInit {
  @ViewChild(MatPaginator) paginator: MatPaginator;
  @ViewChild(MatSort) sort: MatSort;
  @ViewChild('TABLE') table: ElementRef;
  dataSource: DataTableDataSource;

  /** Columns displayed in the table. Columns IDs can be added, removed, or reordered. */
  displayedColumns = ['id', 'name', 'time'];

  ExportTOExcel()
  {
    const ws: XLSX.WorkSheet=XLSX.utils.table_to_sheet(this.table.nativeElement);
    const wb: XLSX.WorkBook = XLSX.utils.book_new();
    XLSX.utils.book_append_sheet(wb, ws, 'Sheet1');

    /* save to file */
    XLSX.writeFile(wb, 'CHNCHR_Data_Sheet.xlsx');

  } 

  ngOnInit() {
    this.dataSource = new DataTableDataSource(this.paginator, this.sort);
  }
}

如果需要component.html：

<div class="mat-elevation-z8" #TABLE>
  <mat-table #table [dataSource]="dataSource" matSort aria-label="Elements">

    <!-- Id Column -->
    <ng-container matColumnDef="id">
      <mat-header-cell *matHeaderCellDef mat-sort-header>Id</mat-header-cell>
      <mat-cell *matCellDef="let row">{{row.id}}</mat-cell>
    </ng-container>

    <!-- Name Column -->
    <ng-container matColumnDef="name">
      <mat-header-cell *matHeaderCellDef mat-sort-header>Name</mat-header-cell>
      <mat-cell *matCellDef="let row">{{row.name}}</mat-cell>
    </ng-container>

    <ng-container matColumnDef="name">
        <mat-header-cell *matHeaderCellDef mat-sort-header>Name</mat-header-cell>
        <mat-cell *matCellDef="let row">{{row.time}}</mat-cell>
      </ng-container>

    <mat-header-row *matHeaderRowDef="displayedColumns"></mat-header-row>
    <mat-row *matRowDef="let row; columns: displayedColumns;"></mat-row>
  </mat-table>

  <mat-paginator #paginator
    [length]="dataSource.data.length"
    [pageIndex]="0"
    [pageSize]="50"
    [pageSizeOptions]="[25, 50, 100, 250]">
  </mat-paginator>
</div>