I have a problem with the Angular paginator - it doesn't work

I have a problem with Angular Material's paginator.

It is instantiated in my class:

@ViewChild("paginator") paginator: MatPaginator;

After getting the data from my API called by ngOnInit(), I set the pager to the data:

this._service.get().subscribe({
      next: (response) => {
        this._dataSource.data = response.Content || [];
        if (this.paginator) {
          this.paginator.pageSize = this.pageSize;
          this.paginator._changePageSize(this.pageSize);
          this._dataSource.paginator = this.paginator;
        }
      },
      error: (error) => {
        this._dialogService.openError(error);
      }
    });

Then I try to force paginator again, but it doesn't work:

ngAfterViewInit() {
    if (this.paginator) {
      this.paginator.pageSize = this.pageSize;
      this.paginator._changePageSize(this.pageSize);
    }
    this._dataSource.paginator = this.paginator;
  }

In my HTML, I have this table:

<table mat-table [dataSource]="_dataSource" multiTemplateDataRows>
      <ng-container matColumnDef="...">
        <th mat-header-cell *matHeaderCellDef> ... </th>
        <td mat-cell *matCellDef="let element"> {{element....}} </td>
      </ng-container>
      <ng-container matColumnDef="...">
        <th mat-header-cell *matHeaderCellDef> ... </th>
        <td mat-cell *matCellDef="let element"> {{element....}} </td>
      </ng-container>
    .......
        <!-- Header & Row Definitions -->
        <tr mat-header-row *matHeaderRowDef="displayedColumns"></tr>
        <tr mat-row *matRowDef="let row; columns: displayedColumns;"></tr>
  
        <tr class="mat-row" *matNoDataRow>
            <td class="mat-cell" [attr.colspan]="displayedColumns.length">
                Data not found
            </td>
        </tr>
    </table>
    <mat-paginator [pageSize]="5" [pageSizeOptions]="[5, 10, 25, 50]" showFirstLastButtons>
    </mat-paginator>
</table> 

You forgot to add the template reference variable in the HTML for the @ViewChild.

<mat-paginator #paginator [pageSize]="5" [pageSizeOptions]="[5, 10, 25, 50]" showFirstLastButtons></mat-paginator>

We can also directly reference the component like below.

@ViewChild(MatPaginator) paginator: MatPaginator;

After doing this the page size is set.

Full Code:

HTML:

<table mat-table [dataSource]="_dataSource" class="mat-elevation-z8">
  <!--- Note that these columns can be defined in any order.
        The actual rendered columns are set as a property on the row definition" -->

  <!-- Position Column -->
  <ng-container matColumnDef="position">
    <th mat-header-cell *matHeaderCellDef>No.</th>
    <td mat-cell *matCellDef="let element">{{element.position}}</td>
  </ng-container>

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

  <!-- Weight Column -->
  <ng-container matColumnDef="weight">
    <th mat-header-cell *matHeaderCellDef>Weight</th>
    <td mat-cell *matCellDef="let element">{{element.weight}}</td>
  </ng-container>

  <!-- Symbol Column -->
  <ng-container matColumnDef="symbol">
    <th mat-header-cell *matHeaderCellDef>Symbol</th>
    <td mat-cell *matCellDef="let element">{{element.symbol}}</td>
  </ng-container>

  <tr mat-header-row *matHeaderRowDef="displayedColumns"></tr>
  <tr mat-row *matRowDef="let row; columns: displayedColumns;"></tr>
</table>
<mat-paginator
  #paginator
  [pageSize]="5"
  [pageSizeOptions]="[5, 10, 25, 50]"
  showFirstLastButtons
></mat-paginator>

TS:

import { Component, ViewChild } from '@angular/core';
import { MatTableDataSource, MatTableModule } from '@angular/material/table';
import { MatPaginator, MatPaginatorModule } from '@angular/material/paginator';
import { of, delay } from 'rxjs';

export interface PeriodicElement {
  name: string;
  position: number;
  weight: number;
  symbol: string;
}

const ELEMENT_DATA: PeriodicElement[] = [
  { position: 1, name: 'Hydrogen', weight: 1.0079, symbol: 'H' },
  { position: 2, name: 'Helium', weight: 4.0026, symbol: 'He' },
  { position: 3, name: 'Lithium', weight: 6.941, symbol: 'Li' },
  { position: 4, name: 'Beryllium', weight: 9.0122, symbol: 'Be' },
  { position: 5, name: 'Boron', weight: 10.811, symbol: 'B' },
  { position: 6, name: 'Carbon', weight: 12.0107, symbol: 'C' },
  { position: 7, name: 'Nitrogen', weight: 14.0067, symbol: 'N' },
  { position: 8, name: 'Oxygen', weight: 15.9994, symbol: 'O' },
  { position: 9, name: 'Fluorine', weight: 18.9984, symbol: 'F' },
  { position: 10, name: 'Neon', weight: 20.1797, symbol: 'Ne' },
];

/**
 * @title Basic use of `<table mat-table>`
 */
@Component({
  selector: 'table-basic-example',
  styleUrl: 'table-basic-example.css',
  templateUrl: 'table-basic-example.html',
  imports: [MatTableModule, MatPaginatorModule],
})
export class TableBasicExample {
  displayedColumns: string[] = ['position', 'name', 'weight', 'symbol'];
  _dataSource = new MatTableDataSource();
  pageSize = 10;
    @ViewChild('paginator') paginator: MatPaginator;

  ngOnInit() {
    of(ELEMENT_DATA)
      .pipe(delay(2000))
      .subscribe({
        next: (response) => {
          this._dataSource.data = response || [];
          if (this.paginator) {
            this.paginator.pageSize = this.pageSize;
            this.paginator._changePageSize(this.pageSize);
            this._dataSource.paginator = this.paginator;
          }
        },
        error: (error) => {
          console.error(error);
        },
      });
  }
}

Stackblitz Demo