GrapheneOS PdfViewer无法打开PDF问题求助（附Logcat日志）

正在构建GrapheneOS的PdfViewer项目，已下载对应子模块，但无法打开PDF文件。使用Windows系统，Logcat输出日志如下：

2022-11-02 00:12:37.712 21225-21279 PdfViewer D  path /viewer.html
2022-11-02 00:12:37.748 21225-21225 chromium  I  [INFO:CONSOLE(0)] "Error with Permissions-Policy header: Unrecognized feature: 'ambient-light-sensor'.", source:  (0)
2022-11-02 00:12:37.748 21225-21225 chromium  I  [INFO:CONSOLE(0)] "Error with Permissions-Policy header: Unrecognized feature: 'battery'.", source:  (0)
2022-11-02 00:12:37.748 21225-21225 chromium  I  [INFO:CONSOLE(0)] "Error with Permissions-Policy header: Unrecognized feature: 'hid'.", source:  (0)
2022-11-02 00:12:37.748 21225-21225 chromium  I  [INFO:CONSOLE(0)] "Error with Permissions-Policy header: Origin trial controlled feature not enabled: 'interest-cohort'.", source:  (0)
2022-11-02 00:12:37.748 21225-21225 chromium  I  [INFO:CONSOLE(0)] "Error with Permissions-Policy header: Unrecognized feature: 'payment'.", source:  (0)
2022-11-02 00:12:37.748 21225-21225 chromium  I  [INFO:CONSOLE(0)] "Error with Permissions-Policy header: Unrecognized feature: 'picture-in-picture'.", source:  (0)
2022-11-02 00:12:37.748 21225-21225 chromium  I  [INFO:CONSOLE(0)] "Error with Permissions-Policy header: Unrecognized feature: 'serial'.", source:  (0)
2022-11-02 00:12:37.749 21225-21225 chromium  I  [INFO:CONSOLE(0)] "Error with Permissions-Policy header: Unrecognized feature: 'speaker-selection'.", source:  (0)
2022-11-02 00:12:37.749 21225-21225 chromium  I  [INFO:CONSOLE(0)] "Error with Permissions-Policy header: Unrecognized feature: 'usb'.", source:  (0)
2022-11-02 00:12:37.749 21225-21225 chromium  I  [INFO:CONSOLE(0)] "Error with Permissions-Policy header: Unrecognized feature: 'xr-spatial-tracking'.", source:  (0)
2022-11-02 00:12:37.752 21225-21279 PdfViewer D  path /pdfjs-dist/webpack.js
2022-11-02 00:12:37.752 21225-21271 PdfViewer D  path /viewer.css
2022-11-02 00:12:37.753 21225-21271 PdfViewer D  path /pdf.js
2022-11-02 00:12:37.760 21225-21271 PdfViewer D  path /viewer.js
2022-11-02 00:12:37.764 21225-21225 chromium  I  [INFO:CONSOLE(1)] "Uncaught SyntaxError: Unexpected token '.'", source: https://localhost/pdf.js (1)
2022-11-02 00:12:37.770 21225-21225 chromium  I  [INFO:CONSOLE(3)] "Uncaught ReferenceError: pdfjsLib is not defined", source: https://localhost/viewer.js (3)
2022-11-02 00:12:37.772 21225-21279 PdfViewer D  path /favicon.ico
2022-11-02 00:12:37.773 21225-21225 chromium  I  [INFO:CONSOLE(203)] "Uncaught ReferenceError: pdfjsLib is not defined", source: https://localhost/viewer.js (203)

问题分析 #

日志中的Permissions-Policy警告属于非致命提示，不会导致PDF无法打开。核心故障链是：

1. pdf.js第1行出现语法错误Unexpected token '.'，说明该文件内容损坏或加载不完整
2. 后续pdfjsLib is not defined报错是连锁反应——pdf.js未能正常加载，导致依赖它的viewer.js找不到核心变量

解决方案 #

• 重新同步子模块：在项目根目录执行git submodule update --init --recursive，确保pdfjs-dist等子模块文件完整无缺失，避免因子模块下载中断导致文件损坏
• 检查本地文件映射：确认本地服务（localhost）正确映射项目文件，直接查看本地pdf.js的开头内容，排查是否存在无效字符或文件截断情况
• 适配语法兼容性：如果使用的Chromium/WebView版本较旧，可能不支持ES6+语法（如可选链?.），需调整项目编译配置，添加Babel转译兼容旧环境
• 清除缓存：清空浏览器或WebView的缓存，避免加载之前缓存的损坏文件

内容的提问来源于stack exchange，提问作者Muhammad Nadeem