After importing the project, only the project file is displayed, not the project structure
Solution
1.点击file->project structure..->Modules
Click the + plus sign in the upper right corner - "import Modules"
2. Select your project and click OK
3. Select import modules from external model on the following page
Select maven, then keep clicking Next, and finally click Finished
4. After the import is as follows, if the project is not displayed, click Add Content Root to add the project path
Then click OK, the main interface normally displays the project structure