D:\Unity 2019.4.0f1\Editor\Data\Resources\PackageManager\BuiltInPackages\com.unity.ugui\Runtime\EventSystem\UIBehaviour.cs(78,16): error CS0246: The type or namespace name 'UIEventData' could not be found (are you missing a using directive or an assembly reference?)
打开工程就报这样的错误，解决思路。找同版本能打开的同学，把
替换过来就可以了
