//显示对话框
 showModal: function () {
 // 显示遮罩层
 var animation = wx.createAnimation({
  duration: 200,
  timingFunction: "linear",
  delay: 0
 })
 this.animation = animation
 animation.translateY(300).step()
 this.setData({
  animationData: animation.export(),
  showModalStatus: true
 })
 setTimeout(function () {
  animation.translateY(0).step()
  this.setData({
  animationData: animation.export()
  })
 }.bind(this), 200)
 },
 //隐藏对话框
 hideModal: function () {
 // 隐藏遮罩层
 var animation = wx.createAnimation({
  duration: 200,
  timingFunction: "linear",
  delay: 0
 })
 this.animation = animation
 animation.translateY(300).step()
 this.setData({
  animationData: animation.export(),
 })
 setTimeout(function () {
  animation.translateY(0).step()
  this.setData({
  animationData: animation.export(),
  showModalStatus: false
  })
 }.bind(this), 200)
 }

/*使屏幕变暗 */
.commodity_screen {
 width: 100%;
 height: 100%;
 position: fixed;
 top: 0;
 left: 0;
 background: #000;
 opacity: 0.2;
 overflow: hidden;
 z-index: 1000;
 color: #fff;
}
/*对话框 */
.commodity_attr_box {
 height: 300rpx;
 width: 100%;
 overflow: hidden;
 position: fixed;
 bottom: 0;
 left: 0;
 z-index: 2000;
 background: #fff;
 padding-top: 20rpx;
}

 <!--屏幕背景变暗的背景 -->
 <view class="commodity_screen" bindtap="hideModal" wx:if="{{showModalStatus}}"></view>
 <!--弹出框 -->
 <view animation="{{animationData}}" class="commodity_attr_box" wx:if="{{showModalStatus}}">在这里写弹出框里面的布局</view>