Angular Material-垫表不渲染来自Rest API的数据 [英] Angular Material - mat-table not rendering data from rest api

问题描述

我一直在尝试从Angular Material中实现此表示例，

I've been trying to implement this table example from Angular Material without luck

我不明白我在做什么错，我的REST端点提供的数据在控制台输出上清晰可见.

I don't understand what I'm doing wrong, the data which is being provided by my REST endpoint is clearly visible on the console output.

我的怀疑是，在渲染表时，数据可能还没有完全加载.感谢您的任何帮助，谢谢！

My suspicions are that maybe the data isn't quite loaded yet, when the table is rendered. Any help is appreciated, thanks!

lap.component.ts

import {Component, OnInit, ViewChild} from '@angular/core';
import {MatPaginator, MatSort, MatTableDataSource} from '@angular/material';
import {Router} from '@angular/router';
import {LapService} from '../shared/services/lap.service';
import {Lap} from '../shared/model/lap.model';

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

  displayedColumns = ['id', 'year', 'lap', 'shortcut flag', 'start place', 'destination place', 'length', 'height difference'];
  dataSource: MatTableDataSource<Lap>;

  @ViewChild(MatPaginator) paginator: MatPaginator;
  @ViewChild(MatSort) sort: MatSort;


  constructor(public rest: LapService, private router: Router) {
  }

  ngOnInit() {
    this.dataSource = new MatTableDataSource(this.getLaps());
    this.dataSource.paginator = this.paginator;
    this.dataSource.sort = this.sort;
  }


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

    if (this.dataSource.paginator) {
      this.dataSource.paginator.firstPage();
    }
  }

  getLaps() {
    this.rest.getLaps().subscribe((data: {}) => {
      console.log(data);
      console.log('Laps');
      return data;
    });
  }
}

lap.component.html

<mat-form-field>
  <input matInput (keyup)="applyFilter($event.target.value)" placeholder="Filter">
</mat-form-field>

<div class="mat-elevation-z8">
  <table mat-table [dataSource]="dataSource" matSort>

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

    <!-- Year Column -->
    <ng-container matColumnDef="year">
      <th mat-header-cell *matHeaderCellDef mat-sort-header> Year </th>
      <td mat-cell *matCellDef="let row"> {{row.year}} </td>
    </ng-container>

    <!-- Lap Column -->
    <ng-container matColumnDef="lap">
      <th mat-header-cell *matHeaderCellDef mat-sort-header> Lap </th>
      <td mat-cell *matCellDef="let row"> {{row.lap}} </td>
    </ng-container>

    <!-- Shortcut Column -->
    <ng-container matColumnDef="shortcut flag">
      <th mat-header-cell *matHeaderCellDef mat-sort-header> Shortcut Flag </th>
      <td mat-cell *matCellDef="let row" [style.color]="row.color"> {{row.shortcut_flag}} </td>
    </ng-container>

    <!-- Start Column -->
    <ng-container matColumnDef="start place">
      <th mat-header-cell *matHeaderCellDef mat-sort-header> Start Place </th>
      <td mat-cell *matCellDef="let row"> {{row.start_place}} </td>
    </ng-container>

    <!-- Destination Column -->
    <ng-container matColumnDef="destination place">
      <th mat-header-cell *matHeaderCellDef mat-sort-header> Destination Place </th>
      <td mat-cell *matCellDef="let row"> {{row.destination_place}} </td>
    </ng-container>

    <!-- Length Column -->
    <ng-container matColumnDef="length">
      <th mat-header-cell *matHeaderCellDef mat-sort-header> Length </th>
      <td mat-cell *matCellDef="let row"> {{row.length}} </td>
    </ng-container>

    <!-- Height Column -->
    <ng-container matColumnDef="height difference">
      <th mat-header-cell *matHeaderCellDef mat-sort-header> Height Difference </th>
      <td mat-cell *matCellDef="let row"> {{row.height_difference}} </td>
    </ng-container>

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

  <mat-paginator [pageSizeOptions]="[5, 10, 25, 100]"></mat-paginator>
</div>

lap.service.ts

import {Injectable} from '@angular/core';
import {HttpClient, HttpHeaders} from '@angular/common/http';
import {Observable} from 'rxjs';
import {map} from 'rxjs/operators';

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

  private lapUrl = 'http://localhost:8080/api/lap';
  private httpOptions = {
    headers: new HttpHeaders({
      'Content-Type': 'application/json'
    })
  };

  constructor(private http: HttpClient) { }

  getLaps(): Observable<any> {
    return this.http.get(this.lapUrl, this.httpOptions).pipe(
      map(this.extractData));
  }

  private extractData(res: Response) {
    return res || {}; // If 'res' is null, it returns empty object
  }

}

推荐答案

您需要创建new MatTableDataSource()，然后在数据接收时将该数据传递到dataSource.data数组.

You need to create new MatTableDataSource() and then on data receiving pass that data to dataSource.data array.

 ngOnInit() {
   // this.dataSource = new MatTableDataSource(this.getLaps());
    this.dataSource = new MatTableDataSource(); // create new object
    this.getLaps(); // forgeted this line
    this.dataSource.paginator = this.paginator;
    this.dataSource.sort = this.sort;
 }

   getLaps() {
     this.rest.getLaps().subscribe((data: {}) => {
       console.log(data);
       console.log('Laps');
       this.dataSource.data = data; // on data receive populate dataSource.data array
       return data;
    });
  }

这篇关于Angular Material-垫表不渲染来自Rest API的数据的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！