場景描述：一般情況下，加入購物車的動畫效果都會是上圖的3的路線，在這篇文章里，我們來實現1和2路線的加入購物車的動效（3路線的動畫效果網上有很多，具體可以參考這篇文章來實現： www.cnblogs.com/greengage/p… ）。

實現方式：不管是上圖中的哪一種效果，我們都是用CSS3里的cubic-bezier（三次貝塞爾曲線）來實現的。具體什么是三次貝塞爾曲線，可以參考這篇文章： www.bbsmax.com/A/RnJWwpbRJ…

#實現流程：

1、獲取屏幕的高度大小

wx.getSystemInfo({//  獲取頁面的有關信息
      success: function (res) {
        wx.setStorageSync('systemInfo', res)
        var ww = res.windowWidth;
        var hh = res.windowHeight;
        that.globalData.ww = ww;
        that.globalData.hh = hh;
      }
    });
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2、獲取點擊的位置（購物車的位置我們定為最上方或者最下方），定義移動距離

/*加入購物車動效*/
  _flyToCartEffect: function (events) {
    //獲得當前點擊的位置，距離可視區域左上角
    var touches = events.touches[0];
    var diff = {
      x: '25px',
      y: app.globalData.hh -touches.clientY-40 + 'px'//向下
      // y: 25- touches.clientY  + 'px'//向上

    },
      style = 'display: block;-webkit-transform:translate(' + diff.x + ',' + diff.y + ') rotate(350deg) scale(0)';  //移動距離
    this.setData({
      isFly: true,
      translateStyle: style
    });
    var that = this;
    setTimeout(() => {
      that.setData({
        isFly: false,
        translateStyle: '-webkit-transform: none;',  //恢復到最初狀態
        isShake: true,
      });
      setTimeout(() => {
        var counts = that.data.cartTotalCounts + that.data.productCounts;
        that.setData({
          isShake: false,
          cartTotalCounts: counts
        });
      }, 200);
    }, 1000);
  },
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3、在css里調用beizer函數

.fiexd-cart.animate{
  animation: aCartScale 200ms cubic-bezier(.17,.67,.83,.67);
  animation-fill-mode: backwards;
}
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aCartScale是，在曲線的最后，實現了個購物車抖動的動畫

@-webkit-keyframes aCartScale{
  0%{
    -webkit-transform: scale(1.1);
  }
  100% {
    -webkit-transform: scale(1);
  }
}
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至此，流程全部介紹完畢，下面是全部的代碼（里面可能有一些沒用的css樣式代碼，讀者可以自行根據需要刪除）：

js代碼：

var app = getApp();
Page({

  /**
   * 頁面的初始數據
   */
  data: {
    isFly:false
  },

  /*添加到購物車*/
  onAddingToCartTap: function (events) {
    //防止快速點擊
    if (this.data.isFly) {
      return;
    }
    this._flyToCartEffect(events);
  },
  /*加入購物車動效*/
  _flyToCartEffect: function (events) {
    //獲得當前點擊的位置，距離可視區域左上角
    var touches = events.touches[0];
    var diff = {
      x: '25px',
      y: app.globalData.hh -touches.clientY-40 + 'px'//向下
      // y: 25- touches.clientY  + 'px'//向上

    },
      style = 'display: block;-webkit-transform:translate(' + diff.x + ',' + diff.y + ') rotate(350deg) scale(0)';  //移動距離
    this.setData({
      isFly: true,
      translateStyle: style
    });
    var that = this;
    setTimeout(() => {
      that.setData({
        isFly: false,
        translateStyle: '-webkit-transform: none;',  //恢復到最初狀態
        isShake: true,
      });
      setTimeout(() => {
        var counts = that.data.cartTotalCounts + that.data.productCounts;
        that.setData({
          isShake: false,
          cartTotalCounts: counts
        });
      }, 200);
    }, 1000);
  },

})
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wxml代碼：

<view class="container detail-container">
  <view class="fixed-btns-box" bindtap="onCartTap">
    <view class="fiexd-cart {{isShake?'animate':''}}">
      <image src="../../imgs/icon/cart@top.png"></image>
      <view wx:if="{{cartTotalCounts>0}}">{{cartTotalCounts}}</view>
    </view>
  </view>

  <view 
  style="position: fixed;right: 50rpx;bottom:100rpx;width: 100rpx;"
  class="add-cart-btn {{product.stock==0?'disabled':''}}" bindtap="onAddingToCartTap">
    <text style="width: 360rpx">加入分享</text>
    <image class="cart-icon" src="../../imgs/icon/cart.png"></image>
    <image id="small-top-img" class="small-top-img {{isFly?'animate':''}}" src="https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1575871576&di=dda9d07660c88bea6553c3279b0a8cf0&imgtype=jpg&er=1&src=http%3A%2F%2Fpic.pc6.com%2Fup%2F2011-9%2F2011926155953.jpg"
      mode="aspectFill" style="{{translateStyle}}"></image>
  </view>


  

  <view class="fixed-btns-box2" bindtap="onCartTap">
    <view class="fiexd-cart {{isShake?'animate':''}}">
      <image src="../../imgs/icon/cart@top.png"></image>
      <view wx:if="{{cartTotalCounts>0}}">{{cartTotalCounts}}</view>
    </view>
  </view>

</view>
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wxss代碼：

.detail-container {
  background-color:#F9F9F9
}
.detail-header-box,.detail-bottom-box{
  background-color: #fff;
}
.detail-topic-img{
  display: flex;
  justify-content: center;
}
.detail-topic-img image{
  width: 100%;
}

.fixed-btns-box{
  position: fixed;
  top:50rpx;
  right:12px;
  width: 80rpx;

}
.fixed-btns-box2{
  position: fixed;
  right:12px;
  width: 80rpx;
  bottom: 50rpx;

}
.fiexd-cart image{
  height: 64rpx;
  width: 64rpx;
}
.fiexd-cart view{
  font-size: 24rpx;
  background-color: #AB956D;
  color: white;
  position: absolute;
  right: 64rpx;
  top: 0rpx;
  height: 36rpx;
  width: 36rpx;
  line-height: 36rpx;
  border-radius: 36rpx;
  text-align: center;
}
.fiexd-cart.animate{
  animation: aCartScale 200ms cubic-bezier(.17,.67,.83,.67);
  animation-fill-mode: backwards;
}

@-webkit-keyframes aCartScale{
  0%{
    -webkit-transform: scale(1.1);
  }
  100% {
    -webkit-transform: scale(1);
  }
}



.product-counts,.add-cart-btn{
  height: 100%;
  display: flex;
  font-size: 24rpx;
  align-items: center;
  justify-content: center;
}
.product-counts{
  width: 50%;
}
.add-cart-btn{
  position: relative;
  flex: 1;
}
.add-cart-btn:active{
  color: #fff;
}
.add-cart-btn.disabled{
  color: #D5D5DB;
}



.small-top-img{
  height: 160rpx;
  width: 160rpx;
  right:6rpx;
  position: absolute;
  opacity: 0;
}
.small-top-img.animate{
  opacity: 1;
  -webkit-transition:all 1000ms cubic-bezier(0.175, 0.885, 0.32, 1.275);
}




.add-cart-btn .cart-icon{
  margin-left: 40rpx;
  height: 32rpx;
  width: 32rpx;
}


.disabled{
    pointer-events: none;
}

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