注意:这纯粹是 IDEA/AS 问题，gradlew clean |构建 > 清洁 |Build > Rebuild 只会浪费你的时间.

Note: this is purely an IDEA/AS issue, gradlew clean | Build > Clean | Build > Rebuild will just waste your time.

这里的大多数解决方案都是在黑暗中盲目刺伤.这是我发现的根本原因:

Most of the solutions here are blind stabbings in the dark. Here's what I found to be the root cause:

1. 某些 .iml 文件可能丢失(可能是因为我们删除了它)，检查模块错误是否有.iml.
2. 如果缺少，请检查 .idea/modules.xml 是否有该模块的条目

1. Some of the .iml files may be missing (maybe because we deleted it), check if the module erroring has .iml.
2. If it is missing, check if .idea/modules.xml has an entry for that module

在同步时，我注意到 IDEA/AS 试图在 .idea/modules.xml 中放入一个新的重复条目，而已经有一个.当同步尝试重置内存中的模块时，此重复条目可能会被处理两次.

While syncing I noticed that IDEA/AS tries to put a new duplicate entry into .idea/modules.xml while there's already one. This duplicate entry is probably disposed of twice while the sync tries to reset the modules in memory.

快速解决方案:为了使它工作，最简单的方法是删除 .idea/modules.xml 和 .iml 文件.另外可能值得删除 .idea/modules/ 文件夹(如果存在).重新启动 Android Studio(无需清除缓存)并从 Gradle 视图或工具栏强制 Gradle 同步以重新创建文件.

Quick Solution: In order to make it work the easiest is to delete .idea/modules.xml along with the .iml files. Additionally may worth deleting .idea/modules/ folder if it exists. Restart Android Studio (no need to clear cache) and force a Gradle sync from Gradle view or toolbar to recreate the files.