无法处理动画-返回零元素

Question

一旦为数据创建服务，动画就会停止工作。看起来是因为最初加载页面时，ng-repeat中没有任何元素（因为它正在获取数据）。似乎与THIS和THIS类似：

错误：

ERROR Error: Unable to process animations due to the following failed trigger transitions @listAnimation has failed due to:

- `query(":enter")` returned zero elements. (Use `query(":enter", { optional: true })` if you wish to allow this.)

动画：

trigger('listAnimation', [
      transition('* => *', [
        query(':enter', style({ opacity: 0}), { optional: true }),
        query(':enter', stagger('150ms', [
          animate('.5s ease-in', keyframes([
            style({ opacity: 0, /*transform: 'translateY(-75px)',*/ offest: 0}),
            style({ opacity: .5, /*transform: 'translateY(35px)',*/ offest: .3}),
            style({ opacity: 1, /*transform: 'translateY(0px)',*/ offest: 1})
          ]))
        ]))
      ])
    ])

HTML：

<div [@listAnimation]>
    <div *ngFor="let member of members" class="member-card">
      member info goes here...
    </div>
</div>

现在在您说"put in { optional: true } like the error message says"之前...我做到了-它消除了错误消息，但实际上并没有使动画正常工作：

trigger('listAnimation', [
      transition('* => *', [
        query(':enter', style({ opacity: 0}), { optional: true }),
        query(':enter', stagger('150ms', [
          animate('.5s ease-in', keyframes([
            style({ opacity: 0, /*transform: 'translateY(-75px)',*/ offest: 0}),
            style({ opacity: .5, /*transform: 'translateY(35px)',*/ offest: .3}),
            style({ opacity: 1, /*transform: 'translateY(0px)',*/ offest: 1})
          ]))
        ]), {optional: true})
      ])
    ])

请记住，在将数据从应用程序组件中删除之前，所有这些都有效。数据在那里，应用程序正常运行，只是此动画不再起作用。

Answer 1

您必须确保仅在members数组不为空时显示列表容器。这样，仅当列表中有内容时，动画才会触发。

<div [@listAnimation] *ngIf="members.length > 0>
    <div *ngFor="let member of members" class="member-card">
      member info goes here...
    </div>
</div>