当您添加新文件并且 Visual Studio 将其设置为错误的构建操作时，可能会发生这种情况.我知道这已经发生了很多次，并且可能会花费很长时间试图弄清楚发生了什么.如果您右键单击该文件并看到构建操作.这应该设置为Android Resource.希望有帮助

This might happen when you add a new file and Visual studio sets it to the wrong build Action. I know this has happened me multiple times and can spend ages trying to figure out what going on. If you right click the file and see the Build action. this should be set to Android Resource. Hope it helps