What a fantastic idea. I have a Huawei round Android Wear watch, so I just grabbed this watch face - thanks!
The lack of nullability info for Android/JDK frameworks is sad and makes the null safety less useful than it could have been. In the early days there was a tool that would try to infer nullability annotations but it didn’t work all that well so JetBrains ended up with their current approach.
It’d be great if post-1.0 a backwards compatible way to solve this was found. Perhaps, in fact, the OpenJDK project would accept contributions of annotations. As Android is now switching to OpenJDK classes as well, it’d help kill two birds with one stone.
The main issue is that annotating everything with @NotNull is really painful. In my own Java code I only used @Nullable but there seemed to be no way to tell IntelliJ to assume @NotNull unless otherwise specified. If there was, it’d be easier to annotate large Java codebases.