我一直在关注Angular Material Data Table分页器教程here。
当他们构造自己的分页器时，他们使用@ViewChild(MatPaginator) paginator: MatPaginator;
在其component.ts文件中。使用此声明，他们以后可以在同一文件中访问属性：
ngAfterViewInit() {
this.paginator.page
.pipe(
tap(() => this.loadLessonsPage())
)
.subscribe();
}
没有问题。
当我在组件中执行相同的操作时：
export class AllMatchesComponent implements OnInit, OnDestroy, AfterViewInit {
...
@ViewChild(MatPaginator) paginator: MatPaginator;
...
ngAfterViewInit(){
console.log(this.paginator);
this.paginator.page
.pipe(
tap(()=> this.loadMatchesPage())
)
.subscribe();
}
...
，我在控制台中收到以下错误：
错误类型错误：无法
读取未定义的属性“页面”
在AllMatchesComponent.ngAfterViewInit（all-matches.component.ts：50）
当我尝试看一下他们的示例repo（转到分支2-data-table-finished）时，代码包含了所有过滤和排序语法，而我在本教程中尚未涉及。换句话说，它们的示例代码与本教程中的步骤并不相似，并且没有其他分支可以更简单的状态捕获代码。
我不知道为什么未定义分页器。有任何想法吗？
我的个人仓库可以在这里找到：
git clone https://github.com/Atticus29/dataJitsu.git
cd dataJitsu
git checkout SO-paginator-freeze
为了方便起见，以下是全部all-matches.component.ts：
import { Component, OnInit, OnDestroy, AfterViewInit, ViewChild } from '@angular/core';
import { D3Service } from '../d3.service';
import { DatabaseService } from '../database.service';
import { TextTransformationService } from '../text-transformation.service';
import * as firebase from 'firebase/app';
import { MatTableDataSource, MatSort } from '@angular/material';
import { MatPaginatorModule } from '@angular/material/paginator';
import { DataSource } from '@angular/cdk/table';
import {MatProgressSpinnerModule} from '@angular/material/progress-spinner';
import { MatchDataSource } from '../matchDataSource.model';
import { AuthorizationService } from '../authorization.service';
import { Subject } from 'rxjs/Subject';
import { tap } from 'rxjs/operators';
import { MatPaginator } from '@angular/material';
@Component({
selector: 'app-all-matches',
templateUrl: './all-matches.component.html',
styleUrls: ['./all-matches.component.scss']
})
export class AllMatchesComponent implements OnInit, OnDestroy, AfterViewInit {
private dataSource: MatchDataSource;
private columnsToDisplay = ['rank','weightClass', 'ageClass','athlete1Name', 'athlete2Name', 'gender','tournamentName','location', 'date', 'matchRating', 'videoUrl']; //TODO make this dynamic somehow
private loading = true;
user: any = null;
private ngUnsubscribe: Subject<void> = new Subject<void>();
private matchCount: number;
private pageSize: number;
@ViewChild(MatPaginator) paginator: MatPaginator;
constructor(private authService: AuthorizationService, private d3Service: D3Service, private dbService: DatabaseService, private textTransformationService: TextTransformationService) { }
ngOnInit() {
this.authService.getCurrentUser().takeUntil(this.ngUnsubscribe).subscribe(user=>{
this.user = user;
},err=>{
console.log(err);
});
this.pageSize = 2;
this.dataSource = new MatchDataSource(this.dbService);
this.dataSource.loadMatches('test', '', '', 0, this.pageSize);
this.dbService.getMatchCount().subscribe(results=>{
this.matchCount = results;
});
}
ngAfterViewInit(){
console.log(this.paginator);
this.paginator.page
.pipe(
tap(()=> this.loadMatchesPage())
)
.subscribe();
}
loadMatchesPage(){
this.dataSource.loadMatches('TODO', '', 'asc', this.paginator.pageIndex, this.paginator.pageSize);
}
ngOnDestroy(){
console.log("onDestroy is called");
this.ngUnsubscribe.next();
this.ngUnsubscribe.complete();
}
}
这是相应的html：
<script type='text/javascript' src='http://d3js.org/d3.v3.min.js'></script>
<script type='text/javascript' src='https://cdn.firebase.com/v0/firebase.js'></script>
<script type='text/javascript' src='d3fire.min.js'></script>
<script type="text/javascript" src="http://mbostock.github.com/d3/d3.js?2.1.3"></script>
<script type="text/javascript" src="http://mbostock.github.com/d3/d3.geom.js?2.1.3"></script>
<script type="text/javascript" src="http://mbostock.github.com/d3/d3.layout.js?2.1.3"></script>
<br>
<div class="" *ngIf='user'>
<div class="spinner-container" *ngIf="loading$">
<mat-spinner id="spinner"></mat-spinner>
</div>
<mat-table #table [dataSource]="dataSource" class="mat-elevation-z8" *ngIf="!loading$">
<!-- TODO add paidStatus to ngIf -->
<ng-container matColumnDef="rank">
<mat-header-cell *matHeaderCellDef> Rank </mat-header-cell>
<mat-cell *matCellDef="let entry"> {{entry.rank}} </mat-cell>
</ng-container>
<ng-container matColumnDef="weightClass">
<mat-header-cell *matHeaderCellDef> Weight Class </mat-header-cell>
<mat-cell *matCellDef="let entry"> {{entry.weightClass}} </mat-cell>
</ng-container>
<ng-container matColumnDef="ageClass">
<mat-header-cell *matHeaderCellDef> Age Class </mat-header-cell>
<mat-cell *matCellDef="let entry"> {{entry.ageClass}} </mat-cell>
</ng-container>
<ng-container matColumnDef="athlete1Name">
<mat-header-cell *matHeaderCellDef> Athlete 1 </mat-header-cell>
<mat-cell *matCellDef="let entry"> {{entry.athlete1Name}} </mat-cell>
</ng-container>
<ng-container matColumnDef="athlete2Name">
<mat-header-cell *matHeaderCellDef> Athlete 2 </mat-header-cell>
<mat-cell *matCellDef="let entry"> {{entry.athlete2Name}} </mat-cell>
</ng-container>
<ng-container matColumnDef="gender">
<mat-header-cell *matHeaderCellDef> Gender </mat-header-cell>
<mat-cell *matCellDef="let entry"> {{entry.gender}} </mat-cell>
</ng-container>
<ng-container matColumnDef="location">
<mat-header-cell *matHeaderCellDef> Location </mat-header-cell>
<mat-cell *matCellDef="let entry"> {{entry.location}} </mat-cell>
</ng-container>
<ng-container matColumnDef="tournamentName">
<mat-header-cell *matHeaderCellDef> Tournament </mat-header-cell>
<mat-cell *matCellDef="let entry"> {{entry.tournamentName}} </mat-cell>
</ng-container>
<ng-container matColumnDef="date">
<mat-header-cell *matHeaderCellDef> Date </mat-header-cell>
<mat-cell *matCellDef="let entry"> {{entry.date | date:'shortDate'}} </mat-cell>
</ng-container>
<ng-container matColumnDef="videoUrl">
<mat-header-cell *matHeaderCellDef> Video </mat-header-cell>
<mat-cell *matCellDef="let entry"> <a href='{{entry.videoUrl}}'>Click</a> </mat-cell>
<!-- <i class="material-icons right">video</i> -->
</ng-container>
<ng-container matColumnDef="matchRating">
<mat-header-cell *matHeaderCellDef> Match Rating </mat-header-cell>
<mat-cell *matCellDef="let entry"> {{entry.matchRating}}</mat-cell>
<!-- <i class="material-icons right">video</i> -->
</ng-container>
<mat-header-row *matHeaderRowDef="columnsToDisplay"></mat-header-row>
<mat-row *matRowDef="let row; columns: columnsToDisplay;"></mat-row>
</mat-table>
<mat-paginator [length]='matchCount' [pageSize]="2" [pageSizeOptions]="[2, 5, 10]"></mat-paginator>
</div>
最佳答案
根据您的模板，您会遇到由于父div中的* ngif指令而试图获取DOM中不存在的ViewChild fir元素的问题。
有一些解决方案：
您可以将* ngIf指令替换为[hidden]，该指令会隐藏父div但将其保留在dom中，因此您的ViewChild引用将起作用
如果您必须坚持使用* ngIf-更复杂，这是为了确保您的子元素可以作为ElementRef被抓取（为其分配ID并在由ngIf设置为true创建它后获取对它的引用），并为您的ViewChild使用setter作为在这个问题上：
https://stackoverflow.com/a/41095677