微信小程序导航栏跟随滑动效果的实现代码

<view class='tabbar'>
<view class='tabitem wx:if="{{tabclick===0?"click":""}}"' bindtap='clicktab' data-index='0'>tab1</view>
<view class='tabitem wx:if="{{tabclick===1?"click":""}}"' bindtap='clicktab' data-index='1'>tab2 </view>
<view class='tabitem wx:if="{{tabclick===2?"click":""}}"' bindtap='clicktab' data-index='2'>tab3 </view>
<view class='underline' animation="{{animationdata}}" style='left:{{isleft}}'></view>
</view>

.tabbar{
height: 80rpx;
background-color:#50b7ea;
width: 100%;
font-size: 28rpx;
color: rgba(255,255,255,0.50);
position: fixed;
top: 0;
left: 0;
display: flex;
justify-content: center;
align-items: center;
z-index: 997;
}
.tabitem{
width: 33.333%;
display: flex;
align-content: center;
justify-content: center;
position: relative;
height: 100%;
font-size: 28rpx;
}
.click{
color: white;
}
.underline{
position: absolute;
content: '';
width: 84rpx;
height: 3px;
background-color:white;
bottom: 0;
} 

data:{
tabclick: 0,
animationdata: {},
 isleft: '12%'
},
swipertab: function (e) {
var that = this;
var index = e.detail.current
console.log(e.detail.current)
var animation = wx.createanimation({
duration: 1000,
timingfunction: "ease",
})
this.animation = animation
if (index === 0) {
animation.translate(0, 0).step();
that.setdata({
animationdata: animation.export()
})
that.setdata({
tabclick: e.detail.current
});
} else if (index === 1) {
var w = wx.getsysteminfosync().windowwidth;
w = w * 0.32
animation.translate(w, 0).step();
that.setdata({
animationdata: animation.export()
})
that.setdata({
tabclick: e.detail.current
});
} else if(index === 2){
var w = wx.getsysteminfosync().windowwidth;
w = w * 0.65
animation.translate(w, 0).step();
that.setdata({
animationdata: animation.export()
})
that.setdata({
tabclick: e.detail.current
});
}
},