webview 模式下，scroll-view 组件的 dragstart/dragging/dragend 事件无法通过 bind:dragstart 冒号写法绑定，只能使用 binddragstart 这种写法。

<scroll-view
  enhanced
  scroll-y
  style="border:1px solid red; height:200px"
  bind:dragstart="eventHandler"
  bind:dragging="eventHandler"
  bind:dragend="eventHandler"
>
  <view>这种写法不起作用</view>
  ...
  <view>这种写法不起作用</view>
</scroll-view>


<scroll-view
  enhanced
  scroll-y
  style="border:1px solid red; height:200px"
  binddragstart="eventHandler"
  binddragging="eventHandler"
  binddragend="eventHandler"
>
  <view>只能这么写</view>
  ...
  <view>只能这么写</view>
</scroll-view>