解决方案:
/sdcard
is a symlink to/storage/emulated/0
.
'/storage/emulated/0/' like a abstract path, you can upload file on sdcard/,and visit it use '/storage/emulated/0/' in android code.For example,if you want to visit a test.txt in '/storage/emulated/0/myFiles/test/test.txt'(code path), you should upload the test.txt in 'sdcard/test/test.txt'(in Device File Explorer,AS).
因此只需要向/sdcard文件夹中上传文件即可。