Expandable table rows in angular 4 with angular material

It is not possible out of the box, but you can solve it with a little custom code. Take a look at this discussion and this solution (not from me, but the basis for this answer).

In short: Use the material table and add a click-method to the rows:

<md-row *mdRowDef="let row; columns: displayedColumns; let index=index" (click)="expandRow(index, row)" #myRow></md-row>

Add a component for the expanded area. The row_detail.html contains the html which is in the expanded area.

@Component({
  selector: 'app-inline-message',
  templateUrl: 'row_detail.html',
  styles: [`
    :host {
      display: block;
      padding: 24px;
      background: rgba(0,0,0,0.03);
    }
  `]
})
export class InlineMessageComponent {
  @Input() content1: string;
  @Input() content2: string;
}

In your component where the table lives you need the method to expand the row. First, add this to your component...

expandedRow: number;
@ViewChildren('myRow', { read: ViewContainerRef }) containers;

... and then add the method:

/**
   * Shows the detail view of the row
   * @param {number} index
   */
expandRow(index: number, row: DataFromRowFormat) {

    if (this.expandedRow != null) {
      // clear old message
      this.containers.toArray()[this.expandedRow].clear();
    }

    if (this.expandedRow === index) {
      this.expandedRow = null;
    } else {
      const container = this.containers.toArray()[index];
      const factory: ComponentFactory<InlineMessageComponent> = this.resolver.resolveComponentFactory(InlineMessageComponent);
      const messageComponent = container.createComponent(factory);

      messageComponent.instance.content1= "some text";
      messageComponent.instance.content2 = "some more text";
    }
}

As mentioned here by Andrew Seguin this is already feasible out of the box: using the when predicate.

See this example: https://stackblitz.com/edit/angular-material-expandable-table-rows (thx to Lakston)

Inside of the mat-table tag you have to use the mat-row component with a matRipple directive. When you click on a row the row element will be assigned to the expandedElement variable:

<mat-row *matRowDef="let row; columns: displayedColumns;"
        matRipple 
        class="element-row" 
        [class.expanded]="expandedElement == row"
        (click)="expandedElement = row">
</mat-row>

But now we have to add our expanded row, that is hidden by default and will be shown if the user clicks on the row above:

<mat-row *matRowDef="let row; columns: ['expandedDetail']; when: isExpansionDetailRow"
        [@detailExpand]="row.element == expandedElement ? 'expanded' : 'collapsed'"
        style="overflow: hidden"> 
</mat-row>

Important is here the already mentioned when predicate. This calls a isExpansionDetailRow function that is defined in the component itself and checks if the row has a detailRow property:

isExpansionDetailRow = (row: any) => row.hasOwnProperty('detailRow');

Since RC0 the first param is the index:

isExpansionDetailRow = (i: number, row: any) => row.hasOwnProperty('detailRow');

If you want to have an expanded view for every row, you have to add an "ExpansionDetailRow" identified by the detailRow property for every row like this:

connect(): Observable<Element[]> {
    const rows = [];
    data.forEach(element => rows.push(element, { detailRow: true, element }));
    return Observable.of(rows);
}

If you would log the rows variable to the console output, it will look like this:

EDIT: COMPLETE EXAMPLE USING DIRECTIVE

Mat Table expandable rows (sorting, pagination and filtering)