android-studio - Why is Android Studio unable to reference classes in Moudle after introducing Moudle?

Question

I introduced a control in a project in the form of Moudle, but when I used it I found that I could not introduce any class in this Moudle

It is also introduced in settings.gradle
It is also introduced in the project structure, but the code in Moudle cannot be referenced when writing code.

Completely deleting Moudle and then re-importing it, or creating a new Moudle and copying the classes into it will not work.
It will be useless to close AS, delete the .idea file in the root directory and then restart it.

Help. . .

Answer 1

Compile project of main module

Answer 2

Requires main module dependency