由于某种原因,我无法导入 ArryaAdapter 和 ArrayList class,它以前可以工作,但我刚刚重新打开了项目,现在它没有了

I cannot import the ArryaAdapter and ArrayList class for some reason, it was working before but I just reopened the project and now it doesn't

错误:

我尝试重建项目。当我将光标移到它上面时,它显示 "Cannot resolve symbol".

试试这个。

转到菜单中的文件 -> 使缓存无效/重新启动 -> Select 使无效并重新启动