The document discusses several common Android architectural patterns including classic Android, MVC, MVP, MVVM, and Clean Architecture. The goal of these patterns is to create apps that are scalable, maintainable, and testable. Classic Android becomes difficult to maintain and test in large apps. MVC separates concerns but violates single responsibility. MVP and MVVM split tasks into smaller testable units, though MVP's presenter acts as a middleman. Clean Architecture aims for independence from frameworks and databases but has many layers. MVVM removes UI code from activities/fragments and enables data binding and easy unit testing.

1. Architectures:
● Classic Android (View Model)
● MVC
● MVP
● MVVM
● Clean
and many more….

2. Goal!
● Scalable (Large scale vision / new features)
● Maintenance (Anyone can be able to understand and edit it)
● Testing (easily testable)

3. Classic Android
View:
● Activity
Data:
● Database
● Webservices

4. Pros:
● Preferable for small apps
Cons:
● Activities and Fragments get bigger and bigger
● Hard to understand for other developers
● Unit testing is impossible
● Implementing new feature takes lot of time
Classic Android

5. Model View Controller (MVC)
Model:
● POJO classes
● Business logic
View:
● Layout resources
Controller:
● Activity
● Fragments
● Adapters

6. Pros:
● UI and business logic is not connected
● Easier to unit test
Cons:
● Huge controllers
● Violates Single Responsibility principles
● Man in the middle (Controller)
Model View Controller (MVC)

7. Model View Presenter (MVP)
View:
● Renders logic
Presenter:
● Handle User events and callbacks
Model:
● Database logic
● REST Helpers

8. Pros:
● Huge tasks split into simpler tasks
● Smaller objects, less bugs
● Easy to unit test
Cons:
● Model can’t be reused, tied to specific user case
● Presenter mainly does the invoking and callback stuff
Model View Presenter (MVP)

9. Clean Architecture
Interactor

10. Pros:
● Independent of Frameworks
● Independent of UI
● Independent of Java
● Independent of Database
Cons:
● Lots of layers
Clean Architecture

11. Model View ViewModel (MVVM)
View:
● Activity
Model:
● POJO classes
ViewModel:
● Interaction with model
● Updating the View

12. Model View ViewModel (MVVM)
● Microsoft pattern
● Removes UI code from Activities / Fragments
● Binding ViewModels to UI (Using databinding)
● Easy unit tests
● No ‘findViewById()’...............

13. XML Code sample
<layout ...>
<data>
<variable .... />
</data>
<TextView ......
android:visibility=”@{viewModel.hasValue ? View.VISIBLE : View.GONE}”>
</TextView>
</layout>
GitHub sample: https://github.com/activesince93/MVVMDemo