<picker class='fr' bindchange="onChangeBuild" range-key="{{'num'}}" value="{{buildIndex}}" range="{{aBuilding}}">
<view class="picker">
罗兰{{aBuilding[buildIndex].num}}幢
</view>
</picker>
range-key中的值要么 range-key="{{'num'}}"，要么range-key="num'"
