vue+cesium初始化地球时遇到问题

1、首先通过vue-cli构建项目，在你习惯的目录下打开cmd输入：

vue init webpack cesium-demo    我这里的cesium-demo是我项目的名称，后续一些构建项目的选项省略.....

2、然后在项目中安装cesium框架： 

npm install cesium --save

3、webpack配置，build/webpack.base.conf.js 文件中添加

resolve: {
    alias: {
        // Cesium module name
        cesium: path.resolve(__dirname, '../node_modules/cesium/Source')
    }
}

4、build/webpack.dev.conf.js 文件中添加

plugins: [
        ...
        // Copy Cesium Assets, Widgets, and Workers to a static directory
        new CopyWebpackPlugin([ { from: path.join('node_modules/cesium/Source', '../Build/Cesium/Workers'), to: 'Workers' } ]),
        new CopyWebpackPlugin([ { from: path.join('node_modules/cesium/Source', 'Assets'), to: 'Assets' } ]),
        new CopyWebpackPlugin([ { from: path.join('node_modules/cesium/Source', 'Widgets'), to: 'Widgets' } ]),
        new webpack.DefinePlugin({
            // Define relative base path in cesium for loading assets
            CESIUM_BASE_URL: JSON.stringify('')
        })
    ]

5、main.js中配置

import Cesium from "cesium/Cesium";
import "cesium/Widgets/widgets.css";

Vue.prototype.Cesium = Cesium
Vue.config.productionTip = false

6、App.vue 中输入以下代码

 <template>
  <div id="app">
    <div id="cesiumContainer"></div>
  </div>
</template>
    
<script>
export default {
  name: "App",
  mounted() {
    this.$nextTick(() => {
      const viewer = new this.Cesium.Viewer("cesiumContainer");
      console.log('viewer: ', viewer);
    });
  },
};
</script>
<style>
html,
body {
   100%;
  height: 100%;
  padding: 0;
  margin: 0;
}
#app,
#cesiumContainer {
  font-family: "Avenir", Helvetica, Arial, sans-serif;
   100%;
  height: 100%;
  overflow: hidden;
}
</style>

运行： npm run dev

项目运行起来之后报错！！！

页面如下，是个空白的

控制台报错： Error in nextTick: "TypeError: Cannot read property 'Viewer' of undefined"

现在问题在这里解决不了，求助！！！！！！！

请问是哪里出了问题，请踊跃评论！！！