小程序 给最外层view设置百分之百高度不起作用

<view class="content">
  <view class="today">
    <view class="info">
      <view class="temp">{{today.wendu}}℃</view>
      <view class="weather">{{today.todayInfo.type}} {{today.todayInfo.fengxiang}} {{today.todayInfo.fengli}}</view>
      <view>友情提示：{{today.ganmao}}</view>
      <view class="city">{{city}}</view>
    </view>
  </view>
  <import src="../template/itemtpl" />
  <view class="future">
    <block wx:for="{{future}}" wx:key="*this">
      <template is="future-item" data="{{item}}" />
    </block>
  </view>
</view>

.content{
    font-family : 微软雅黑,宋体;
    font-size: 14px;
    background-size:cover;  
    height: 100%;
    width:100%;
}