<view class="top_tabbar" > 
 <block wx:for="{{itemName}}" wx:key="{{index}}">
   <view class="item_name {{tabIndex == index ? 'active' : ''}}" bindtap="handleItem" data-index="{{index}}">
    <text>{{item}}</text>
   </view>
 </block>
</view>

.top_tabbar{
 width: 100%;
 background-color: #ffffff;
 display: flex;
 position: fixed;
}
.item_name{
 text-align: center;
 margin:20rpx 60rpx;
 color: grey;
}
.active{
 color: lightgreen;
}
.active text{
  padding-bottom: 10rpx;
  border-bottom: 4rpx solid lightgreen;
}

data:{
  itemName: ["軍事", "明星", "動漫","風(fēng)景"],
  tabIndex: 0
 },
//獲取點擊事件
handleItem(e){
  // console.log(e)
  const index = e.currentTarget.dataset.index
  this.setData({
   tabIndex: index
  })
 }