Angular 5材质垫选择：根据选择的值进行过滤，

Question

因此，我有一个使用Angular Material Data Table的Angular 5应用程序，并且在该应用程序上具有过滤，排序，分页等功能。现在，我可以根据用户在输入字段中输入的值进行过滤，这可以工作。现在，我希望基于选择输入具有相同的功能。因此，用户可以使用2个输入：1个输入字段，用户可以在其中键入文本，1个选择字段，用户可以在其中选择一个选项。我希望我的表也可以根据用户选择的选项进行过滤，但是现在不起作用。

这是我的HTML：

<div class="filterContainer" *ngIf="showDataForm">
  <mat-form-field>
    <input matInput (keyup)="applyFilter($event.target.value)" placeholder="Search">
  </mat-form-field>
</div>

<div class="filterSelectContainer" *ngIf="showDataForm">
  <mat-select placeholder="Search EADDPStage">
    <mat-option *ngFor="let stage of EADDPStages[0]" [value]="stage" (onSelectionChange)="applySelectFilter($event, stage)">
      {{stage}}
    </mat-option>
  </mat-select>
</div>

<div class="container">
  <mat-table #table class="dataTable" *ngIf="showDataForm;else loadingTemplate" [dataSource]="dataSource" matSort>
    <ng-container matColumnDef="EOTAFileNr">
      <mat-header-cell *matHeaderCellDef mat-sort-header>EOTAFileNr</mat-header-cell>
      <mat-cell *matCellDef="let item">{{item.EOTAFileNr}}</mat-cell>
    </ng-container>
    <ng-container matColumnDef="ProcessRTAB">
      <mat-header-cell *matHeaderCellDef mat-sort-header>ProcessRTAB</mat-header-cell>
      <mat-cell *matCellDef="let item">{{item.ProcessRTAB}}</mat-cell>
    </ng-container>
    <ng-container matColumnDef="EADDPStage">
      <mat-header-cell *matHeaderCellDef mat-sort-header>EADDPStage</mat-header-cell>
      <mat-cell *matCellDef="let item">{{item.EADDPStage}}</mat-cell>
    </ng-container>
    <ng-container matColumnDef="RegistrationDate">
      <mat-header-cell *matHeaderCellDef mat-sort-header>RegistrationDate</mat-header-cell>
      <mat-cell *matCellDef="let item">{{item.RegistrationDate}}</mat-cell>
    </ng-container>

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

  <mat-paginator *ngIf="showDataForm" [pageSize]="10" [pageSizeOptions]="[5, 10, 25]" showFirstLastButtons></mat-paginator>
</div>

<ng-template #loadingTemplate>
  <div>
      <p>Please wait, the data is loading...</p>
      <img src="../../assets/giphy.gif">
  </div>
</ng-template>

<button mat-raised-button class="submitButton" color="accent" (click)="logout()">Logout and remove cookie</button>

这是我的TS文件：

import { Component, OnInit, ChangeDetectorRef, ViewChild, ElementRef } from '@angular/core';
import { Router } from '@angular/router';
import { CookieService } from 'ngx-cookie-service';
import { LoginService } from '../Services/login.service';
import { TableService } from '../Services/table.service';
import { EADProcess } from '../Classes/EADProcess';
import { MatTableDataSource, MatPaginator, MatSort } from '@angular/material';
import { Observable } from 'rxjs/Observable';
import { of } from 'rxjs/observable/of';
import { map, tap, catchError } from 'rxjs/operators';

@Component({
  selector: 'app-table',
  templateUrl: './table.component.html',
  styleUrls: ['./table.component.css']
})
export class TableComponent implements OnInit {

  sort;
  paginator;

  showDataForm = false;

  stringArray: string[] = [];
  eadItems: EADProcess[] = [];
  EADDPStages: string[] = [];

  dataSource: MatTableDataSource<EADProcess>;

  // @ViewChild(MatPaginator) paginator: MatPaginator;
  @ViewChild(MatPaginator) set contentPaginator(contentPaginator: ElementRef) {
    this.paginator = contentPaginator;
    if (this.paginator) {
      this.dataSource.paginator = this.paginator;
    }
  }
  @ViewChild(MatSort) set contentSort(contentSort: ElementRef) {
    this.sort = contentSort;
    if (this.sort) {
      this.dataSource.sort = this.sort;
    }
  }

  // which columns the data table needs to display
  columnsToDisplay: string[] = ['EOTAFileNr', 'ProcessRTAB', 'EADDPStage', 'RegistrationDate'];

  constructor(private router: Router,
              private cookieService: CookieService,
              private loginService: LoginService,
              private tableService: TableService,
              private chRef: ChangeDetectorRef) {

  }

  ngOnInit() {
    const $this = this;

    this.getEADDPStages();
  }

  public getEADDPStages() {
    const json: any = {(data omitted for example)};

    const jsonStringified = JSON.stringify(json);

    this.tableService.getEADDPStages(jsonStringified).subscribe(res => {
      this.convertJsonEADDPStagesToArray(res);
      this.getAllEadItems();
    });
  }

  public getAllEadItems() {
    const json: any = {(data omitted for example)};

    const jsonStringified = JSON.stringify(json);

    this.tableService.getAllEadItems(jsonStringified).subscribe(res => {
      this.convertJsonResultToArray(res);
      this.dataSource = new MatTableDataSource(this.eadItems);
      this.dataSource.paginator = this.paginator;
      this.showDataForm = true;
    });
  }

  public applyFilter(filterValue: string) {
    filterValue = filterValue.trim();
    filterValue = filterValue.toLowerCase();
    this.dataSource.filter = filterValue;
  }

  public applySelectFilter(event: Event, filterValue: string) {
    filterValue = filterValue.trim();
    filterValue = filterValue.toLowerCase();
    this.dataSource.filter = filterValue;
  }

  public convertJsonResultToArray(res: any) {
    this.stringArray = JSON.parse(res);
    for (const eadItem of this.stringArray) {
      const ead = new EADProcess();
      ead.id = eadItem['GUID'];
      ead.titel = eadItem['Title'];
      ead.EADDraftingStage = eadItem['EADDraftingStage'];
      ead.EOTAFileNr = eadItem['EOTAFileNr'];
      ead.ProcessRTAB = eadItem['ProcessRTAB']['LookupValue'];
      ead.EADDPStage = eadItem['EADDPStage'];
      ead.RegistrationDate = this.formatDate(eadItem['RegistrationDate']);

      this.eadItems.push(ead);
    }
  }

  public formatDate(date) {
    const d = new Date(date);
    let month = '' + (d.getMonth() + 1);
    let day = '' + d.getDate();
    const year = d.getFullYear();

    if (month.length < 2) {
      month = '0' + month;
    }
    if (day.length < 2) {
      day = '0' + day;
    }

    return [year, month, day].join('-');
  }

  public convertJsonEADDPStagesToArray(res: any) {
    const arr = JSON.parse(res);
    for (const item of arr['ReturnExtraValues']) {
      this.EADDPStages.push(item);
    }
    const len = this.EADDPStages[0].length;
    this.EADDPStages[0][len.toString()] = 'Closed';
  }

  public logout() {
    this.cookieService.delete('logindata');
    this.loginService.setLoggedIn(false);
    this.router.navigateByUrl('/login');
  }

}

现在，页面加载确实发生了什么，它将为加载到“ EADDPStages [0]”中的每个项目执行“ onSelectionChange”事件！因此它将加载，进入第一个项目，然后进入applySelectFilter方法，然后看到它具有第二个选项，再次进入applySelectFilter方法，第三个项目，等等。它将执行此操作，直到页面完全加载为止，那么似乎没有应用过滤器。当我从mat-select中选择一个选项时，它将再次遍历所有值，而我想要的只是根据我选择的值应用过滤器！

有人看到潜在的问题吗？

Answer 1

我认为从Angular 5开始不推荐使用(onSelectionChange)。我建议根据Angular Material 5 Docs使用(selectionChange)。使用该方法，您可以检测到用户何时进行选择，并将过滤器应用于所选项目。

在您的标记中：

<div class="filterSelectContainer" *ngIf="showDataForm">
  <mat-select placeholder="Search EADDPStage" (selectionChange)="selectStage($event)">
    <mat-option *ngFor="let stage of EADDPStages[0]" [value]="stage">
      {{stage}}
    </mat-option>
  </mat-select>
</div>

在您的代码背后：

selectStage(event) {
  applyFilter(event.value);
}