问题
Can I use main expansion file as optional download option in application? So I don't need download it with APK file but later when user would do it.
回答1:
When you create an expansion file, it should be something like
[main|patch].<version>.<package_name>
main, is for files that you're app needs to run, so you choose patch. The version is the same apk version you are uploading the expansion file with. If your apk version is 7 you should name the expansion file as follow:
patch.7.com.yourpackagename
You then zip it, and upload to google play!
来源：https://stackoverflow.com/questions/25830667/android-apk-expansion-file-optional