选择模块设置并进行这些更改，它将工作

在文件>项目结构>模块中，点击“+”按钮，

根据你的项目添加新的模块，比如Java或RUBY之类的 然后应用，ok

intellij密切 删除。idea文件夹 重启intellij 单击导入，选择您的项目 从现有资源创建项目，单击下一步，下一步，下一步

你应该可以出发了。

尝试重新导入Maven项目。|文件类型|忽略文件和文件夹。

将“Project”下拉菜单改为“Project Files”

我知道这并没有回答涉及Maven模块的OPs问题，但这是截至2021年7月谷歌上的第一个搜索结果，当时试图调试为什么文件夹在IntelliJ中不能正确显示

I have a better solution that worked for me and it might work for you. No need to delete the whole .idea folder as this way you lose the whole project. It is possible that you just accidentally excluded all folders in project settings. I also found that project folders disappeared. I was trying to find out how to disable indexing, so I was looking at Project Settings -> Modules and I clicked on Excluded to see if I could add the whole project there to ignore it for indexing. It didn't do anything and I couldn't drag and drop the folder under Excluded. What I didn't realize is that simply clicking "Excluded", IntelliJ automatically moves the folder to Excluded and all folders disappeared in Project Explorer. "Excluded" button changes background to gray, which means exclusion is active. This is a very poor user interface because it is hardly noticeable and clicking this button has a far-reaching impact on your project.

Fix:

打开项目设置->模块 如果“排除”突出显示，单击它 单击应用或关闭

结果: 项目中的文件夹再次显示出来

非常糟糕的UI设计!源和排除按钮看起来像标签时，他们的工作实际上是“复选框”!

注意，仅仅单击Sources或Excluded似乎是一个没有任何可见效果的选项卡选择，但它具有深远的影响，基本上是从构建过程中添加或删除文件。

对于我在IntelliJ，它显示我一个弹出框导入现有的项目作为gradle项目。我只是点击确定，然后文件夹结构显示正确。