一.Cannot find getter for field
我定义的变量为：private String mWord;但是get方法是这样的：getmWord()
解决方法就是改成getMWord
二.警告: Schema export directory is not provided to the annotation processor
so we cannot export the schema. You can either provide `room.schemaLocation`
annotation processor argument OR set exportSchema to false.
如图设置一下就行