Android-Architectures

Project Description :

Connect With a REST - API and retrieve list of countries in Mvc , Mvp and Mvvm Architectures.

Countries API to be connected with

https://restcountries.eu/rest/v2/all

A Free Api to respond with countries list in JSON ; We are going to use country names to display a list as a part of this exercise.

Adapters Used :

• RX Java , RX Android

• RetroFit , RetroFit Adapter For RX Java , Gson Converters

MVC : Model - View - Controller

Concept : To Split the implementation as per data model ; presentation layer ; and controller flows

How it fits with Android ?

• In android an Activity manages layout + Business logic .

• Mvc makes an activity to set it's View (Layout) alone and makes it dependent on controller for model operations.

Conclusions :

Separation of Concerns is done as below :

• Model -- Controls the connection with API and retrieval of Countries list

• View -- Controls all Actions related to GUI (Activity)

• Controller -- Business logic here to retrieve country list and delegate back to handle success or Failure scenarios.

Pain Points :

• A tight coupling between activity and controller ; but better than keeping every thing in an activity .

MVP : Model - View - Presenter

• Starts with providing a solution for the problem which MVC creates ; A tight coupling or one - one relation between view and controller

• In an enterprise project this creates a roadblock on maintainability

• MVP Addresses this problem by Abstracting the View as an interface

Separation of Concerns :

• Presenter (A.K.A) generalised controller will not be connected to a view directly but instead to an interface of view .

• It solves the tight coupling between view and controller as view can be easily swapped with another view implementing the interface as per the business requirement .

Pain Points :

• Though Presenter is un aware of the view it's calling ,view knows exactly to what presenter it's bounded to it .

• More over , Presenter is now allowed to call back view with out dependency to the state of the user .

MVVM : Model - View - ViewModel

• Solves the problem of Presenter directly calling the view alongside many advantages on unit testing the module making it modular

Seperation of Concerns :

• Model connects with the API and emits events to ViewModel

• View Model will handle those events and update it's state to serve view when requested.

• view model basically updates it's local information and stays up to date with model , view can use that information as per it's requirement .

Advantages :

• No tight coupling between View and View model ; and this pattern even separates activity which has Android API dependency from model and view model

• It enables for easy unit testing on business logic as it's a normal java programme.

###Screenshots for the app Created

Screen to Retry when countries list is unavilable