Lightweight BaseFragment - boilerplate reduction

[IvanToplak]

I've noticed boilerplate code when overriding lifecycle methods: we have to call parent method for each override (call to super).
Some developers don't follow best practices for when to call super (i.e. is it before or after setup/cleanup code).
It's possible to enforce those rules and remove call to super from Fragments by creating BaseFragment that would:

• extend Fragment and override lifecycle methods,
• make overrides final so that they can't be overridden in Fragments,
• declare setup/cleanup methods: protected open fun do[lifecycleMethodName] that we can override in Fragments,
• call setup/cleanup methods at correct locations in overrides.

This is inspired by template method design pattern.

Correct locations of setup/cleanup method calls:

• onCreate, onViewCreated, onStart, onResume - after call to super
• onPause, onStop, onDestroy, onDestroyView - before call to super.

Example of that kind of method in BaseFragment:

    final override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        doOnViewCreated(view, savedInstanceState)
    }

    protected open fun doOnViewCreated(view: View, savedInstanceState: Bundle?) {}

For example when we want to override onViewCreated in a Fragment we would override doOnViewCreated instead.

Add clear warning to Kdoc of BaseFragment that it should be lightweight and it's not intended to hold methods that could be extension functions. We don't want another View superclass.

[julianfalcionelli]

I think what you propose is good! I am also one of those who use a BaseFragment/BaseActivity to reduce the boilerplate code.
We just need to be careful to not add too many things in the Base classes.