XML files in a project often report errors for no reason, but it does not affect the running of the program, which is really intolerable to people like me, so I searched online, I can turn off the validation of XML, and it will not report errors again. The operation is as follows: Window — Preferences — Validation, as shown in the figure

PS: Also, if you have similar validation errors for other types of files, you can remove the validation for the corresponding file type. At the same time, in order to improve the startup and compilation speed of the project, you can remove the validation of some files appropriately.