mat-sort 不适用于 mat-table

Question

我的 mat-table 工作正常，但是当按照官方 api 文档添加 mat-sort 时，它在 ngAfterViewInit 失败并显示以下消息

Cannot set property 'sort' of undefined at ViewFeedbackComponent.ngAfterViewInit

关于这个问题已经有一个 SO post（见下文 link）但我仍然无法让它工作。

有人发现问题了吗？官方示例使用组件本身定义的 "static" MatTableDataSource，但是我从后端查询。

非常感谢任何帮助！

MatSortModule 已经在 app.module.ts 中导入，mat-sort-header 指令应用于列并且 ngAfterViewInit 已经与官方示例中的完全一样...

import {  Component,  OnInit,  ViewEncapsulation,  ViewChild,  AfterViewInit} from '@angular/core';
import {  Feedback} from '../../../../../models/feedback';
import {  FeedbackService} from '../../services/feedback.service';
import {  MatTableDataSource,  MatSort} from '@angular/material';


@Component({
  selector: 'app-view-feedback',
  templateUrl: './view-feedback.component.html',
  styleUrls: ['./view-feedback.component.css'],
  encapsulation: ViewEncapsulation.Emulated
})
export class ViewFeedbackComponent implements OnInit, AfterViewInit {

  feedbacks: Feedback[] = [];
  showSpinner: boolean = true;
  displayedColumns: String[] = [
    'id',
    'user',
    'timestamp',
    'stars'
  ];
  dataSource: MatTableDataSource < Feedback > ;

  @ViewChild(MatSort) sort: MatSort;

  constructor(private _feedbackService: FeedbackService) {}

  ngOnInit() {
    this._feedbackService.getFeedback.subscribe(
      res => {
        this.feedbacks = res;
        this.dataSource = new MatTableDataSource(this.feedbacks);
      }
    );

  }

  ngAfterViewInit() {
    this.dataSource.sort = this.sort;
  }


}

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

    <!-- column definitions -->
    <ng-container matColumnDef="id">
      <mat-header-cell *matHeaderCellDef mat-sort-header>Id</mat-header-cell>
      <mat-cell *matCellDef="let r"> {{r._id}} </mat-cell>
    </ng-container>

    <ng-container matColumnDef="user">
      <mat-header-cell *matHeaderCellDef mat-sort-header>User Id</mat-header-cell>
      <mat-cell *matCellDef="let r"> {{r.user}} </mat-cell>
    </ng-container>

    <ng-container matColumnDef="timestamp">
      <mat-header-cell *matHeaderCellDef mat-sort-header>Date</mat-header-cell>
      <mat-cell *matCellDef="let r"> {{r.timestamp}} </mat-cell>
    </ng-container>

    <ng-container matColumnDef="stars">
      <mat-header-cell *matHeaderCellDef mat-sort-header>Stars</mat-header-cell>
      <mat-cell *matCellDef="let r"> {{r.stars}} </mat-cell>
    </ng-container>

    <!-- tbl display settings -->
    <mat-header-row *matHeaderRowDef="displayedColumns"></mat-header-row>
    <mat-row *matRowDef="let row; columns: displayedColumns;"></mat-row>

  </mat-table>

Answer 1

问题是下一段代码

  ngAfterViewInit() {
    this.dataSource.sort = this.sort;
  }

发生在您实际获得 table 订阅之前：

  ngOnInit() {
    this._feedbackService.getFeedback.subscribe(
      res => {
        this.feedbacks = res;
        this.dataSource = new MatTableDataSource(this.feedbacks);
      }
    );

  }

作为一种可能的解决方案，您可以通过 Observable.zip 同步 ngAfterViewInit 调用和 getFeedback 订阅。请参考RxJS zip documentation

Answer 2

我正在使用旧版本 angular-material 中的前一个排序方法示例。最新的 angular-material 排序示例使用 ngAfterViewInit() 调用排序 this.dataSource.sort = this.sort; 我无法使用新示例进行排序。旧的排序方法使用 extends DataSource 。我能够使用新路径 `import { DataSource } from '@angular/cdk/table';

导入 DataSource

import { Component, ViewChild, Inject, OnInit, ElementRef } from '@angular/core';
import { MatTableDataSource, MatSort } from '@angular/material';
import { DataSource } from '@angular/cdk/table';
import { Observable } from 'rxjs/Observable';
import { HttpClient, HttpResponse, HttpHeaders, HttpRequest} from '@angular/common/http';
import 'rxjs/add/operator/startWith';
import 'rxjs/add/observable/merge';
import 'rxjs/add/observable/of';
import 'rxjs/add/operator/map';

export interface Data {}

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})

export class AppComponent implements OnInit {

  myData: Array < any > ;
  displayedColumns = ['id', 'name'];

  dataSource: MyDataSource;

  @ViewChild(MatSort) sort: MatSort;

  constructor(private http: HttpClient) {}

 getData() {
    let url = 'https://api.mydatafeeds.com/v1.1/cumulative_player_data.json?';
    let headers = new HttpHeaders({ "Authorization": "123ykiki456789123456" });
    this.http.get(url, {headers})
      .subscribe(res => {
        this.myData = res;
        this.dataSource = new MyDataSource(this.myData, this.sort);
      });
  }

  ngOnInit() {
    this.getData();
  }
}

export class MyDataSource extends DataSource < any > {
  constructor(private dataBase: Data[], private sort: MatSort) {
    super();
  }
  /** Connect function called by the table to retrieve one stream containing the data to render. */
  connect(): Observable < Data[] > {
    const displayDataChanges = [
      Observable.of(this.dataBase),
      this.sort.sortChange,
    ];

    return Observable.merge(...displayDataChanges).map(() => {
      return this.getSortedData();
    });
  }

  disconnect() {}

  /** Returns a sorted copy of the database data. */
  getSortedData(): Data[] {
    const data = this.dataBase.slice();
    if (!this.sort.active || this.sort.direction == '') { return data; }

    return data.sort((a, b) => {

      let propertyA: number | string = '';
      let propertyB: number | string = '';

      switch (this.sort.active) {
        case 'id':
          [propertyA, propertyB] = [a.id, b.id];
          break;
        case 'name':
          [propertyA, propertyB] = [a.name, b.name];
          break;

      }

      let valueA = isNaN(+propertyA) ? propertyA : +propertyA;
      let valueB = isNaN(+propertyB) ? propertyB : +propertyB;

      return (valueA < valueB ? -1 : 1) * (this.sort.direction == 'asc' ? 1 : -1);
    });

  }

}

<mat-table #table [dataSource]="dataSource" matSort>
  <ng-container matColumnDef="id">
    <mat-header-cell *matHeaderCellDef mat-sort-header> Id </mat-header-cell>
    <mat-cell *matCellDef="let data"> <b>{{data.id}}.</b>
    </mat-cell>
  </ng-container>
  <ng-container matColumnDef="name">
    <mat-header-cell *matHeaderCellDef mat-sort-header> Id </mat-header-cell>
    <mat-cell *matCellDef="let data"> <b>{{data.name}}.</b>
    </mat-cell>
  </ng-container>
  <mat-header-row *matHeaderRowDef="displayedColumns"></mat-header-row>
  <mat-row *matRowDef="let data; columns: displayedColumns;"></mat-row>
</mat-table>

Answer 3

我重新定义了继承自 MatTableDataSource 的连接方法坏主意...

Answer 4

在 angular 7 中，对两个分页器使用以下示例，但将分页器替换为排序。

https://stackblitz.com/edit/data-table-multiple-data-source

这里是这个问题的副本：

Answer 5

对此的简单解决方案不是在 ngAfterViewInit 中声明排序，而是在从 "this._feedbackService.getFeedback.subscribe" 获得结果后声明。

解决方法如下

  ngOnInit() {
    this._feedbackService.getFeedback.subscribe(
      res => {
        this.feedbacks = res;
        this.dataSource = new MatTableDataSource(this.feedbacks);

        this.dataSource.sort = this.sort; //this will solve your problem

      }
    );

  }

上面那个对我来说很合适。

谢谢，

Answer 6

确保在从 API

获取数据时添加了 {static: false}

@ViewChild(MatSort, {static: false}) sort: MatSort;

Answer 7

要使 matSort 正常工作，类型定义很重要，至少我是这么认为的。所以在代码中使用 type as any ：数据源：MatTableDataSource；不起作用。必须在此处定义一个类型才能使其工作，尝试定义一个接口并将其传递到 MatTableDataSource 的泛型中。此外，matColumnDef 必须匹配定义类型的属性名称。

Answer 8

不需要重新初始化对象，只需要更改数据即可

  ngOnInit() {
    this._feedbackService.getFeedback.subscribe(
      res => {
        this.feedbacks = res;

        // this.dataSource = new MatTableDataSource(this.feedbacks);
        // this.dataSource.sort = this.sort; //this will solve your problem
        // becomes
        this.dataSource.data = this.feedbacks

      }
    );

  }

mat-sort 不适用于 mat-table

mat-sort not working on mat-table

angular-material

angular

angular-cdk