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Practice with Coroutines Flow, ViewModel and get data with Retrofit from two APIs

Project example for learn ViewModel, flow and Coroutines with fetching data with retrofit from two Apis

Show data with logd on MainActivity.class onCreate() method

        override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        val networkHelper = NetworkHelper(this)
        postViewModel =
        ViewModelProvider(this, ViewModelFactory(networkHelper))[PostViewModel::class.java]
           myViewModel =
             ViewModelProvider(this, ViewModelFactory(networkHelper))[MyViewModel::class.java]

        postViewModel.getUserWithPost().observe(this) {
           when (it) {
            is UserResource.Loading -> {
                Log.d(tag, "onCreate: Loading...")
            }
            is UserResource.Error -> {
                Log.d(tag, "onCreate: ${it.message}")
            }
            is UserResource.Success -> {
                Log.d(tag, "onCreate: ${it.userWithPost.userList}")
                Log.d(tag, "onCreate: ${it.userWithPost.postList}")
            }
          }
        }
           myViewModel.liveEvent.postValue("PDP")
           myViewModel.liveEvent.observe(this, Observer {
         })
        }

Note

/**

  • A lifecycle-aware observable that sends only new updates after subscription, used for events like

  • navigation and Snackbar messages.

  • This avoids a common problem with events: on configuration change (like rotation) an update

  • can be emitted if the observer is active. This LiveData only calls the observable if there's an

  • explicit call to setValue() or call().

  • Note that only one observer is going to be notified of changes. */

         class SingleLiveEvent<T> : MutableLiveData<T>() {

     private val mPending = AtomicBoolean(false)

     @MainThread
     override fun observe(owner: LifecycleOwner, observer: Observer<in T>) {

      if (hasActiveObservers()) {
        Log.w(TAG, "Multiple observers registered but only one will be notified of changes.")
       }

       // Observe the internal MutableLiveData
         super.observe(owner, Observer { t ->
           if (mPending.compareAndSet(true, false)) {
            observer.onChanged(t)
              }
           })
          }

          @MainThread
           override fun setValue(t: T?) {
           mPending.set(true)
           super.setValue(t)
           }

          /**
            * Used for cases where T is Void, to make calls cleaner.
            */

            @MainThread
             fun call() {
             value = null
               }

              companion object {

               private const val TAG = "SingleLiveEvent"
                }
               }

Used Libraries

ViewModelScope

implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:2.4.0"

Coroutines

implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.5.2'
implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.5.2'

Retrofit

implementation 'com.squareup.retrofit2:retrofit:2.9.0'
implementation 'com.squareup.retrofit2:converter-gson:2.9.0'