微信小程序实现页面浮动导航

<view class='container'>
<view class='navigation {{pageVariable.isFloat == true ? "float-navigation":""}}'>
  <view class='{{policyFilter.curSelectNavigationItemFormate(pageVariable.curSelectedItemId,"0")}}' data-id='0' catchtap='selectNavigationItem'>全部</view>
  <view class='{{policyFilter.curSelectNavigationItemFormate(pageVariable.curSelectedItemId,"1")}}' data-id='1' catchtap='selectNavigationItem'>保障中</view>
  <view class='{{policyFilter.curSelectNavigationItemFormate(pageVariable.curSelectedItemId,"2")}}' data-id='2' catchtap='selectNavigationItem'>已生效</view>
  <view class='{{policyFilter.curSelectNavigationItemFormate(pageVariable.curSelectedItemId,"3")}}' data-id='3' catchtap='selectNavigationItem'>未生效</view>
 </view>
</view>

.navigation {  /*导航样式*/
 width: 100%;
 display: flex;
 justify-content: space-around;
 align-items: center;
 height: 80rpx;
 background-color: #fff;
 font-size: 28rpx;
 color: #333;
 font-weight: 500;
 box-shadow: inset 0 0 0 0 rgba(0, 0, 0, 0.30);
}
 
.float-navigation {  /*导航浮动起来的css*/
 position: fixed;
 top: 0;
 z-index: 1000;
}
 
.navigation-item-selected {  /*导航项选中的样式*/
 color: #40a0ee;
 height: 80rpx;
 line-height: 80rpx;
 border-bottom: 3rpx solid #40a0ee;
}

Page({
  data:function () {
  var model = {};
  model.pageVariable = {
   curSelectedItemId:'0', //顶部导航栏，当前选中的项
   isFloat:false, //控制导航栏浮动
  }
  return model;
 }(),
 /**
  * 选择导航
  */
 selectNavigationItem:function(e){
  this.setData({
   'pageVariable.curSelectedItemId': e.currentTarget.dataset.id,
   'pageVariable.isFloat':false
  });
  wx.pageScrollTo({
   scrollTop: 0,
  });
  this.initData(e.currentTarget.dataset.id);  //加载数据
 },
 onPageScroll:function(res){
  if (res.scrollTop >= 1){ //开始滚动
   if (!this.data.pageVariable.isFloat){
    this.setData({
     'pageVariable.isFloat':true
    });
   }
  }else{
   this.setData({
    'pageVariable.isFloat': false
   });
  }
 }
})