代码如下，请问如何通过点击van-sidebar-item项改变{{activeKey}}的值，实现box_1的内容显示与隐藏。

<view class="side">
  <van-sidebar active-key="{{ activeKey }}" bind:change="onChange">
    <van-sidebar-item title="标签名 1" />
    <van-sidebar-item title="标签名 2" />
    <van-sidebar-item title="标签名 3" />
  </van-sidebar>
  <van-notify id="van-notify" />
</view>
<view class="box_1" wx:if="{{activeKey == 0}}">11</view>
<view class="box_1" wx:elif="{{activeKey == 1}}">22</view>

data{
  activeKey: 0,
},
onChange(event) {
  Notify({ type: 'primary', message: event.detail });
},