小程序开发中如何实现一个底部弹出模态框功能

<view class="modals modals-bottom-dialog" hidden="{{hideModal}}" >
 <view class="modals-cancel" bindtap="hideModal"></view>
 <view class="bottom-dialog-body bottom-pos" animation="{{animationData}}">
 <view class="comment_top">
  <view></view>
  <view class="comment_num">{{comment.length}}条评论</view>
  <view class="comment_close" bindtap="hideModal">×</view>
 </view>
 <view class="comment_list">
  <view class="comment_li" wx:for="{{comment}}" wx:key="{{index}}">
  <image class="comment_li_img" src="{{item.headpic}}"></image>
  <view class="comment_li_info">
   <view class="comment_li_name">{{item.nickname}}</view>
   <view class="comment_li_content">{{item.memo}}
   <text class="comment_li_date">9-24</text>
   </view>
  </view>
  </view>
 </view>
 <view class="comment_inputbox">
  <input class="comment_input" maxlength="120" adjust-position value="{{commentform}}" bindinput="commentinput" placeholder="有何高见，讲来听听"></input>
  <view class="comment_sendbtn" bindtap="sendcomment">发送</view>
 </view>
 </view>
</view>

/* 评论 */
/*模态框*/
.modals{
 position:fixed;
 z-index: 100000;
 top:0; 
 left: 0; 
 right:0; 
 bottom: 0;
 }
.modals-cancel{
 position:absolute; 
 z-index:1000; 
 top:0; 
 left: 0; 
 right:0; 
 bottom: 0; 
 /* background-color: rgba(0,0,0,.5); */
 }
.bottom-dialog-body{
 width: 99%;
 margin: 0 auto;
 position:absolute; 
 z-index:10001; 
 bottom:0; 
 left:0; 
 right:0; 
 height:65%; 
 background-color: #fff;
 border-top-left-radius: 10rpx;
 border-top-right-radius: 10rpx;
 overflow: hidden;
 display: flex;
 flex-direction: column;
 }
/*动画前初始位置*/
.bottom-pos{
 -webkit-transform:translateY(100%);
 transform:translateY(100%);
}
.comment_top{
 width: 100%;
 display: flex;
 justify-content: space-between;
 align-items: center;
 border-bottom: 1rpx solid #f2f2f2;
 padding: 10rpx 24rpx;
 box-sizing: border-box;
}
.comment_num{
 font-size: 30rpx;
}
.comment_close{
 font-size: 62rpx;
 line-height: 50rpx;
}
.comment_list{
 flex: 1;
 overflow: hidden;
}
.comment_li{
 display: flex;
 padding: 10rpx 24rpx;
 box-sizing: border-box;
}
.comment_li_img{
 width: 40rpx;
 height: 40rpx;
 border-radius: 50%;
 margin-right: 16rpx;
}
.comment_li_info{
 flex: 1;
}
.comment_li_name{
 font-size: 30rpx;
}
.comment_li_content{
 font-size: 28rpx;
}
.comment_li_date{
 color: #999;
 font-size: 24rpx;
 margin-left: 20rpx;
}
.comment_inputbox{
 display: flex;
 padding: 20rpx 24rpx;
 box-sizing: border-box;
 align-items: center;
 justify-content: space-between;
 border-top: 1rpx solid #f2f2f2;
}
.comment_input{
 font-size: 30rpx;
 flex: 1;
}
.comment_sendbtn{
 font-size: 30rpx;
 background: #dd5923;
 color: #fff;
 padding: 5rpx 18rpx;
 border-radius: 10rpx;
}

Page({
 data: {
 hideModal: true, //模态框的状态 true-隐藏 false-显示
 animationData: {},
 },
 
 // 显示遮罩层
 showModal: function () {
 var that = this;
 that.setData({
  hideModal: false
 })
 var animation = wx.createAnimation({
  duration: 600,//动画的持续时间 默认400ms 数值越大，动画越慢 数值越小，动画越快
  timingFunction: 'ease',//动画的效果 默认值是linear
 })
 this.animation = animation
 setTimeout(function () {
  that.fadeIn();//调用显示动画
 }, 200)
 },

 // 隐藏遮罩层
 hideModal: function () {
 var that = this;
 var animation = wx.createAnimation({
  duration: 800,//动画的持续时间 默认400ms 数值越大，动画越慢 数值越小，动画越快
  timingFunction: 'ease',//动画的效果 默认值是linear
 })
 this.animation = animation
 that.fadeDown();//调用隐藏动画 
 setTimeout(function () {
  that.setData({
  hideModal: true
  })
 }, 720)//先执行下滑动画，再隐藏模块

 },

 //动画集
 fadeIn: function () {
 this.animation.translateY(0).step()
 this.setData({
  animationData: this.animation.export()//动画实例的export方法导出动画数据传递给组件的animation属性
 })
 },
 fadeDown: function () {
 this.animation.translateY(300).step()
 this.setData({
  animationData: this.animation.export(),
 })
 },
})