android - Why there's a separate MutableLiveData subclass of LiveData?

Question

It looks like MutableLiveData differs from LiveData only by making the setValue() and postValue() methods public, whereas in LiveData they are protected.

What are some reasons to make a separate class for this change and not simply define those methods as public in the LiveData itself?

Generally speaking, is such a form of inheritance (increasing the visibility of certain methods being the only change) a well-known practice and what are some scenarios where it may be useful (assuming we have access to all the code)?

Answer 1

In LiveData - Android Developer Documentation, you can see that for LiveData, setValue() & postValue() methods are not public.

Whereas, in MutableLiveData - Android Developer Documentation, you can see that, MutableLiveData extends LiveData internally and also the two magic methods of LiveData is publicly available in this and they are setValue() & postValue().

setValue(): set the value and dispatch the value to all the active observers, must be called from main thread.

postValue() : post a task to main thread to override value set by setValue(), must be called from background thread.

So, LiveData is immutable. MutableLiveData is LiveData which is mutable & thread-safe.