Android Jetpack Architecture Components: Getting Started | raywenderlich.com

🎓 Courses & Articles
1

In this tutorial, you will learn how to create a contacts app using Architecture Components from Android Jetpack like Room, LiveData and ViewModel.

This is a companion discussion topic for the original entry at https://www.raywenderlich.com/6729-android-jetpack-architecture-components-getting-started
2

Excellent article! I have doubt in one of the snippet shown here.

Inside PeopleDetailsViewModel we have following method.

fun getPeopleDetails(id: Int): LiveData<People> {
    peopleId.value = id
    val peopleDetails = Transformations.switchMap<Int, People>(peopleId) { id ->
      peopleRepository.findPeople(id)
    }
    return peopleDetails
  }

What it does is, every-time we call getPeopleDetails, it will always initialise peopleDetails and return the new instance. Actually this kills the purpose of having Transformations.switchMap. I believe it should be update to following snippet.

Updated ViewModel code

init {
    peopleData = Transformations.switchMap<Int, People>(peopleId) { id ->
      peopleRepository.findPeople(id)
    }
  }

  fun getPeopleLiveData() = peopleData

  fun refreshPeople(id: Int) {
    peopleId.value = id
  }

Fragment Code

viewModel.getPeopleLiveData().observe(this, Observer { peopleDetails ->
     populatePeopleDetails(peopleDetails)
})

// Find people with provided id

val peopleId = arguments?.getInt(getString(R.string.people_id))
            
peopleId?.let {
   viewModel.refreshPeople(peopleId)
}

So in above case, whenever id changes, refreshPeople method will be called by fragment, it will set new id on peopleId LiveData, which will in turn trigger switchMap call to findPeople.

Let me know If my understanding is correct.

3

@zr.faisal Can you please help with this when you get a chance? Thank you - much appreciated! :]

4

Hi @vipshah, thanks for highlighting and yes, your understanding is perfect! The above code is demonstrated in such way just to introduce audiences with the LiveData Transformations feature and explain with easy, of course in real use-cases there are always room for improvements just like you showed one. We will definitely update that in the next revisions. Thanks again! :slight_smile:

5

thanks very much for your wonderful article , I really learnt a lot

just a question, I used to work with mvvm architecture , what do you suggest as a professional ? which architecture do you prefer to use ?

thanks in advance

6

Glad that you liked this article and learned something new from it!

As a professional, you should go for the app architecture which is more comfortable to all your team members and allows you to write simpler and maintainable code. MVVM is a better choice for such case now a days!

My personal favourite is MVVM + Databinding for architecting Android apps.

I would recommend you reading this book:
https://store.raywenderlich.com/products/advanced-android-app-architecture
so that you can compare with other popular app architectures out there and choose the one that suites best for you.

Happy coding! :]

7

This tutorial is more than six months old so questions are no longer supported at the moment for it. Thank you!