微信小程序如何实现消息框弹出动画

Page({
 data: {
 showModalStatus: false
 },
 powerDrawer: function(e) {
 var currentStatu = e.currentTarget.dataset.statu;
 this.util(currentStatu)
 },
 util: function(currentStatu) {
 /* 动画部分 */
 // 第1步：创建动画实例 
 var animation = wx.createAnimation({
  duration: 300, //动画时长 
  timingFunction: "linear", //线性 
  delay: 0 //0则不延迟 
 });

 // 第2步：这个动画实例赋给当前的动画实例 
 this.animation = animation;

 // 第3步：执行第一组动画 
 animation.opacity(0).rotateY(100).step();

 // 第4步：导出动画对象赋给数据对象储存 
 this.setData({
  animationData: animation.export()
 })

 // 第5步：设置定时器到指定时候后，执行第二组动画 
 setTimeout(function() {
  // 执行第二组动画 
  animation.opacity(1).rotateY(0).step();
  // 给数据对象储存的第一组动画，更替为执行完第二组动画的动画对象 
  this.setData({
  animationData: animation
  })

  //关闭 
  if (currentStatu == "close") {
  this.setData({
   showModalStatus: false
  });
  }
 }.bind(this), 200)

 // 显示 
 if (currentStatu == "open") {
  this.setData({
  showModalStatus: true
  });
 }
 }

})

<!--button-->
<view class="btn bubble" bindtap="powerDrawer" data-statu="open">登录</view>

<!--mask-->
<view class="drawer_screen" bindtap="powerDrawer" data-statu="close" wx:if="{{showModalStatus}}"></view>
<!--content-->
<!--使用animation属性指定需要执行的动画-->
<view animation="{{animationData}}" class="drawer_box" wx:if="{{showModalStatus}}">

 <!--drawer content-->
 <view class="drawer_title">消息框</view>
 <view class="drawer_content">
 </view>
 <view class="btn_ok" bindtap="powerDrawer" data-statu="close">确定</view>
</view>

/*button*/

.btn {
 width: 80%;
 padding: 20rpx 0;
 border-radius: 10rpx;
 text-align: center;
 margin: 40rpx 10%;
 background: #07c160;
 color: #fff;
}

/*mask*/

.drawer_screen {
 width: 100%;
 height: 100%;
 position: fixed;
 top: 0;
 left: 0;
 z-index: 1000;
 background: #000;
 opacity: 0.4;
 overflow: hidden;
}

/*content*/

.drawer_box {
 width: 650rpx;
 overflow: hidden;
 position: fixed;
 top: 50%;
 left: 0;
 z-index: 1001;
 background: #fafafa;
 margin: -150px 50rpx 0 50rpx;
 border-radius: 3px;
}

.drawer_title {
 padding: 15px;
 font: 20px "microsoft yahei";
 text-align: center;
}

.text {
 font: 20px "microsoft yahei";
 text-align: center;
}

.drawer_content {
 height: 80px;
 overflow-y: scroll; /*超出父盒子高度可滚动*/
}

.btn_ok {
 padding: 10px;
 font: 20px "microsoft yahei";
 text-align: center;
 border-top: 1px solid #e8e8ea;
 color: #3cc51f;
}

.bottom {
 padding-bottom: 20px;
}

.bubble {
 position: relative;
 overflow: hidden;
}

.bubble:after {
 content: "";
 background: #999;
 position: absolute;
 width: 750rpx;
 height: 750rpx;
 left: calc(50% - 375rpx);
 top: calc(50% - 375rpx);
 opacity: 0;
 margin: auto;
 border-radius: 50%;
 transform: scale(1);
 transition: all 0.4s ease-in-out;
}

.bubble:active:after {
 transform: scale(0);
 opacity: 1;
 transition: 0s;
}