<template>
  <view class="my_main">
    <!-- 页面内容 -->
  </view>
</template>

mounted() {
  console.log('窗口变化前,my_main的高度为:',
  document.querySelector('.my_main').style.height)
  // 获取初始页面高度
  let mainHeight = document.body.offsetHeight
  console.log('mainHeight', mainHeight)
  // 监听页面高度变化window.onresize,
  window.onresize = function () {
    console.log('窗口变化了:')
    let Height = document.body.offsetHeight
    console.log('mainHeight', mainHeight)
    console.log('Height', Height)
    if(mainHeight > Height){
      document.querySelector('.my_main').style.height = mainHeight + 'px'
    } else {
      document.querySelector('.my_main').style.height = '94vh'
    }
  }
},