MVVM & Nested Fragments/Views: ViewModel Contracts
summary
Claim: define small interface-based ViewModel Contracts that fragments expect and pass the parent ViewModel class in their arguments so fragments obtain the parent instance via ViewModelProvider and cast it to the contract. Uses LiveData, ViewModelProvider/ViewModelFactory, LiveData transformations and simple extension helpers. Built a registration flow (username email interests + persistent progress card) and refactor removes the activity as mediator, yields plug-and-play reusable fragments and clearer state mapping instead of a monolithic shared ViewModel. Sample code on GitHub; approach works in production.
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chapters (8)
- 0:00Introduction and motivation
- 1:07Fragment communication challenges
- 5:38Registration flow example
- 8:47MVVM and ViewModel basics
- 12:36ViewModel contracts concept
- 16:24Implementation steps
- 21:59Key benefits and takeaways
- 23:06Resources and conclusion
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