在 Angular 中打印所选行的行号

Question

我正在使用 Angular 8 构建一个单页应用程序。我有一个表，其值现在硬编码在 .ts 文件中，如下所示： displayedColumns = ['select', 'position', 'name', 'weight', 'symbol'];  dataSource = new MatTableDataSource<Element>(ELEMENT_DATA);  selection = new SelectionModel<Element>(true, []);const ELEMENT_DATA: Element[] = [  {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'},];我在 .ts 文件中编写了一个函数来输出所选行，如下所示：selectedRow() {        const rowNumber = this.selection.selected;        console.log("row number that is selected : " + rowNumber);    }然后，html 文件实现代码来显示该表以及复选框，如下所示：<div class="example-container mat-elevation-z8">  <mat-table #table [dataSource]="dataSource">    <!-- Checkbox Column -->    <ng-container matColumnDef="select">      <mat-header-cell *matHeaderCellDef>        <mat-checkbox (change)="$event ? masterToggle() : null"                      [checked]="selection.hasValue() && isAllSelected()"                      [indeterminate]="selection.hasValue() && !isAllSelected()">        </mat-checkbox>      </mat-header-cell>      <mat-cell *matCellDef="let row">        <mat-checkbox (click)="$event.stopPropagation(); selectedRow()"                      (change)="$event ? selection.toggle(row) : null"                      [checked]="selection.isSelected(row)">        </mat-checkbox>      </mat-cell>    </ng-container>    <!-- Position Column -->    <ng-container matColumnDef="position">      <mat-header-cell *matHeaderCellDef> No. </mat-header-cell>      <mat-cell *matCellDef="let element"> {{element.position}} </mat-cell>    </ng-container>现在应用程序中会显示一个行表。SelectedRow() 函数在以下行中实现<mat-checkbox (click)="$event.stopPropagation(); selectedRow()"因此，当我选中任何特定行中的复选框时，就会调用该函数。但该函数的输出是所选的行号：这意味着不显示实际的行号。我计划在此之后实现的功能将需要行号或所选行中的某种值。谁能告诉我为什么没有检索到行号信息？下面是表的屏幕截图和行选择的输出。

Answer 1

可以参考下面的代码，

  <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" -->

<ng-container matColumnDef="select">

      <mat-header-cell *matHeaderCellDef>

        <mat-checkbox (change)="selectAll()"

                      [checked]="allSelected"

                      [indeterminate]="!allSelected && oneSelected">

        </mat-checkbox> 

      </mat-header-cell>

      <mat-cell *matCellDef="let element">

        <mat-checkbox (change)="change(element)" [checked]="element.selected">

        </mat-checkbox>

      </mat-cell>

    </ng-container>

  <!-- 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>

打字稿

export interface PeriodicElement {

  name: string;

  position: number;

  weight: number;

  symbol: string;

  selected?:boolean

}

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',

  styleUrls: ['table-basic-example.css'],

  templateUrl: 'table-basic-example.html',

})

export class TableBasicExample {

  displayedColumns: string[] = ['select','position', 'name', 'weight', 'symbol'];

  dataSource = ELEMENT_DATA

  oneSelected=false;

  allSelected=false;

 change(element:PeriodicElement){

   let e= this.dataSource.find(item=>item.position===element.position);

   if(e){

      e.selected=true;

   }

   this.oneSelected=this.dataSource.filter(item=>item.selected).length>0

 }

 selectAll(){

   if(this.allSelected || !this.oneSelected){

   this.dataSource.forEach(item=>item.selected= false);  

   this.allSelected=true;

   }else{

     this.dataSource.forEach(item=>item.selected= true);

     this.allSelected=false;

     this.oneSelected=false;

   }

 }

}