我想在网格列表中显示卡片,但它没有响应

Here is the code:

<md-grid-list cols="4">
  <md-grid-tile *ngFor="let card of cards">
    <md-card>
      <img md-card-image src="{{card.image}}">
      <md-card-content>
        {{card.content}}
      </md-card-content>
    </md-card>
  </md-grid-tile>
</md-grid-list>