ant-design-vue/components/alert/demo/banner.md

#### 顶部公告 页面顶部通告形式，默认有图标且`type` 为 'warning'。 #### Banner Display Alert as a banner at top of page.

<template>
  <div>
    <a-alert message="Warning text" banner />
    <br />
    <a-alert message="Very long warning text warning text text text text text text text" banner closable />
    <br />
    <a-alert :showIcon="false" message="Warning text without icon" banner />
    <br />
    <a-alert type="error" message="Error text" banner />
  </div>
</template>