uni-app获取设备底部安全区高度，解决自定义底部tabBar

// app.vue
onLaunch: function () {
   const result = uni.getSystemInfoSync();
   this.globalData.safeareaHeight = result.screenHeight - result.safeArea.bottom;
}

// components/menu.vue
<template>
    <view>
      <view>
        <view>导航一</view>
        <view>导航二</view>
        <view>导航三</view>
        <view>导航四</view>
      </view>
      <view
        :style="{ paddingBottom: safeareaHeight + 'px' }"
        class="safearea"
      ></view>
    </view>
</template>

<script>
const app = getApp();
export default {
  data() {
    return {
      safeareaHeight: 0,
    };
  },
  mounted() {
    if (app.globalData.safeareaHeight > 0) {
      this.safeareaHeight = app.globalData.safeareaHeight;
    }
  }
};
</script>