中间粉红的区域高度自适应,不管换什么机型，高度都自适应

<template>
  <!-- 合同-待确认 -->
  <view class="viewport">
    <!-- 上 -->
    <view class="top-box">
      <!-- tab -->
      <view class="tabs">
        <text
          v-for="(item, index) in tabArr"
          :key="item.id"
          class="text"
          :class="{ active: index === activeIndex }"
          @tap="handleClickTab(item, index)"
          >{{ item.title }}</text
        >
      </view>
      <!-- tab的scroll-view -->
      <scroll-view
        v-for="(val, index) in tabArr"
        :key="val.id"
        v-show="activeIndex === index"
        :scroll-y="true"
        class="scroll-view"
      >
        <view v-show="activeIndex === 0" class="base-box">
          <view>33333333333</view>
          <view>33333333333</view>

          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
          <view>54555555553343</view>
        </view>
        <view v-show="activeIndex === 1" class="contract-content-box">
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
          <view>1111111111111111</view>
        </view>
        <view v-show="activeIndex === 2" class="service-plan-box">
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
          <view>999999999999999999999999</view>
        </view>
      </scroll-view>
    </view>
    <!-- 下 -->
    <view class="bottom-box">
      <!-- canvas -->
      <view class="canvas-main-box">
        <!-- 签名 -->
        <view class="canvas-name-box">
          <view class="worker">评估师签字</view>
          <view v-show="!isShowImg">
            <canvas
              @touchstart="handleStart"
              @touchmove="handleMove"
              @touchend="handleEnd"
              class="canvas-box"
              canvas-id="firstCanvas"
              id="firstCanvas"
            ></canvas>
          </view>
          <view class="btn-box">
            <view v-show="isRestBtn" class="reset-btn" @click="handleReset">
              <up-button type="error" text="重签"></up-button>
            </view>
            <view v-show="isClear" class="clear-btn" @click="handleClear">
              <up-button type="success" text="清空"></up-button>
            </view>
            <view class="ok-btn" @click="handleImg">
              <up-button type="primary" text="确定"></up-button>
            </view>
          </view>
        </view>
      </view>
      <!-- 按钮 -->
      <view class="btn-box">
        <view class="btn-save">
          <u-button type="primary" shape="circle" text="保存"></u-button>
        </view>
        <view class="btn-submit">
          <u-button color="#f59a23" type="primary" shape="circle" text="提交"></u-button>
        </view>
      </view>
    </view>

    <!-- 基本信息 -->
    <!-- <view class="base-info-box" v-show="activeIndex === 0">
      <BaseInfo></BaseInfo>
    </view> -->

    <!-- 合同内容 -->
    <!-- <view class="contract-content-box" v-show="activeIndex === 1">
      <ContractContent></ContractContent>
    </view> -->

    <!-- 服务计划 -->
    <!-- <view class="service-plan-box" v-show="activeIndex === 2">
      <ServicePlan></ServicePlan>
    </view> -->
  </view>
</template>