update：场景截图案例代码结构的修改

src/examples/sceneSet/sceneScreenshot/sceneScreenshot-function.js

-let viewer;  // 全局声明viewer
-
-export function addSceneScreenshot() {
-    const script = document.createElement('script');
-    script.src = 'https://cesium.com/downloads/cesiumjs/releases/1.99/Build/Cesium/Cesium.js';
-    script.onload = () => {
-        window.Cesium.Ion.defaultAccessToken = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJqdGkiOiI3Njg4ZWU5Yi1iZDhiLTRhYmUtOTRiYS04YjM5NmUwNjVmMDMiLCJpZCI6MjI3MzQ3LCJpYXQiOjE3MjA1MjA4Mjh9.E5XW4LnwgfVAaBC-znaYr61m4yK0-j2qEQhi9qwFFPE'
-
-        viewer = new window.Cesium.Viewer('cesiumContainer', {
-            navigationHelpButton: false, // 是否显示帮助信息控件
-            infoBox: true,  // 是否显示点击要素之后显示的信息
-            fullscreenButton: false, // 全屏显示
-            CreditsDisplay: false,
-            contextOptions: {
-                webgl: {
-                    alpha: true,
-                    depth: true,
-                    stencil: true,
-                    antialias: true,
-                    premultipliedAlpha: true,
-                    // 通过canvas.toDataURL()实现截图需要将该项设置为true
-                    preserveDrawingBuffer: true,
-                    failIfMajorPerformanceCaveat: true
-                }
-            }
-        });
-    };
-    document.head.appendChild(script);
-
-    const link = document.createElement('link');
-    link.rel = 'stylesheet';
-    link.href = 'https://cesium.com/downloads/cesiumjs/releases/1.119/Build/Cesium/Widgets/widgets.css';
-    document.head.appendChild(link);
-}
-
-export function exportImage(){
+export function exportImage(viewer){
     // 获取场景的canvas
     const canvas = viewer.scene.canvas;
     // 创建一个临时的a标签用于下载图片

src/examples/sceneSet/sceneScreenshot/sceneScreenshot.vue

 <template>
     <div id="cesiumContainer" class="cesium-container"></div>
-    <button @click="exportImage()" class="btn-class">下载场景图片</button>
+    <button @click="exportImage(viewer)" class="btn-class">下载场景图片</button>
 </template>
+
 <script setup>
 import { onMounted } from 'vue';
-import { addSceneScreenshot, exportImage } from './function';
+import { exportImage } from './function';
+
+let viewer;
 
 onMounted(() => {
-    addSceneScreenshot()
+    const script = document.createElement('script');
+    script.src = 'https://cesium.com/downloads/cesiumjs/releases/1.99/Build/Cesium/Cesium.js';
+    script.onload = () => {
+        window.Cesium.Ion.defaultAccessToken = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJqdGkiOiI3Njg4ZWU5Yi1iZDhiLTRhYmUtOTRiYS04YjM5NmUwNjVmMDMiLCJpZCI6MjI3MzQ3LCJpYXQiOjE3MjA1MjA4Mjh9.E5XW4LnwgfVAaBC-znaYr61m4yK0-j2qEQhi9qwFFPE'
+
+        viewer = new window.Cesium.Viewer('cesiumContainer', {
+            navigationHelpButton: false, // 是否显示帮助信息控件
+            infoBox: true,  // 是否显示点击要素之后显示的信息
+            fullscreenButton: false, // 全屏显示
+            CreditsDisplay: false,
+            contextOptions: {
+                webgl: {
+                    alpha: true,
+                    depth: true,
+                    stencil: true,
+                    antialias: true,
+                    premultipliedAlpha: true,
+                    // 通过canvas.toDataURL()实现截图需要将该项设置为true
+                    preserveDrawingBuffer: true,
+                    failIfMajorPerformanceCaveat: true
+                }
+            }
+        });
+
+        
+    };
+    document.head.appendChild(script);
+    const link = document.createElement('link');
+    link.rel = 'stylesheet';
+    link.href = 'https://cesium.com/downloads/cesiumjs/releases/1.119/Build/Cesium/Widgets/widgets.css';
+    document.head.appendChild(link);
 });
 </script>
 
 <style>
 .cesium-container {
-width: 100%;
-height: 100vh;
+    width: 100%;
+    height: 100vh;
 }
 .btn-class {
     position: absolute;