flutter File 写入文件失败问题

File 写入文件出错：FileSystemException: Cannot create file, path = '/storage/emulated/0/Download/xxx.pdf' (OS Error: File exists, errno = 13)

出错机型：华为 nova 5 pro
Android 10

解决方案：
AndroidManifest.xml

<application
        ...
        android:requestLegacyExternalStorage="true"
>