MVVM on Android by Sami Lassed

MVVM on Android by Sami Lassed

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GDG Montreal

February 26, 2019
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  1. MVVM on Android – Architectural Standpoint Senior Android Tech Lead

    @ Bell Canada + Sami LASSED, twitter: @SamiLassed
  2. I am going to talk about: • What is MVVM?

    • MVVM Architecture in General • MVVM Architecture on Android • Benefits of using MVVM on Android
  3. What is MVVM? • It stands for Model View ViewModel

    • Also referred as Model-View-Binder • Introduced on 2005 by Ken Cooper, Ted Peters, and John Gossman • Architectural Pattern
  4. MVVM Architecture Representational Diagram View ViewModel Model Binder Repository The

    Binder is a markup language based on Declarative-Data and Command-Binding
  5. MVVM Architecture The Binder = Data Binding Library <?xml version="1.0"

    encoding="utf-8"?> <android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" …..> <TextView android:id="@+id/featureSettingTitle" ……… android:text="@{viewmodel.title}" app:layout_constraintLeft_toLeftOf="@id/leftSafeAreaGuideline" app:layout_constraintTop_toTopOf="parent" />
  6. MVVM Architecture on Android Representational Diagram Activity/Fragment (View) ViewModel Model

    ViewModel Android Architectural Component Coroutines Android Architectural Component
  7. Detailed MVVM Architecture on Android MVVM + Clean Architecture Pattern

    View ViewModel Service Layer ViewModel Android Architectural Component Coroutines Android Architectural Component ViewModel Helper (Activity, Fragment) Service 1 Service 2 Service 3 Service N Repository Data Model Dummy activity/fragment A loosely coupled view Lightweight, clean code and easy to manage ViewModels SRP 1) Fetch, Store then Update. 2) Update from cache, Ftech, Store then Update. Caching Manager
  8. Detailed MVVM Architecture on Android View Layer • Less boiler

    plate code on view layer by using Data Binding Lib. • Easy to test UI (higher testing coverage) • Activity is not needed to test UI <TextView android:id="@+id/featureSettingTitle" ……… android:text="@{viewmodel.title}" ………… app:layout_constraintTop_toTopOf="parent" /> class ServiceView(override rootView: ViewGroup) : BaseView(rootView), OverviewAdapter.OverviewListener, ServiceContract.View { ………. /** * Hiding Shimmer View */ override fun hideShimmer() { super.hideShimmer() rootView.shimmerView.visibility = View.GONE
  9. Detailed MVVM Architecture on Android Activity == ViewModelHelper ??? •

    ViewModel First Approach • Less responsibilities à à à is request permission View’s responsibility??? • Very simple and lightweight, View shouldn’t be complex. • Easy to test (Also, Testing UI is independent from System)
  10. Detailed MVVM Architecture on Android Service Layer • Applying SRP

    (Single Responsibility Principle) to main components. • Loosely coupled components/logic • Again, Easy to test logic à Higher testing coverage à better quality. • Easy to maintain and support.
  11. Detailed MVVM Architecture on Android ViewModel • Less complicated ViewModel

    • Extensible ViewModels: PlugAndPlay approach, by plugging or removing any service(s) at any time, without major changes.
  12. Detailed MVVM Architecture on Android Service Layer, Example class CreditCardInfoService(private

    val baseViewModel: BaseViewModel, private val paymentAPI: IPaymentApi): IPaymentInfoService { //OR inject the ones above using DI ………….. override fun validateCreditCardInfo(transaction: Transaction,…..) { ………. paymentAPI.validateCreditCard ( headers, payload,…..) { override fun onApiSuccess(response: Response) { …… } }) } }
  13. Benefits of using MVVM on Android • Less boilerplate code/Clean

    Code, especially on View Layer. • DECOUPLING • Highly maintainable code (Support teams) • Easy supporting • Easy testing
  14. Thank You

  15. MVVM on Android – Architectural Standpoint Senior Android Tech Lead

    @ Bell Canada + Sami LASSED, twitter: @SamiLassed