Android MVP

Events

Coroutines

This is a small library (less than 70KB) that will help you through your Android features development in order to keep things simple, clear and tidy.

Please refer to this article to get a more in-depth explanation about how this library and its components work.

Setup

Add implementation or api (library projects) dependency

implementation "com.github.marcherdiego.mvp:events:LATEST_VERSION" 

// Optional if you want to use coroutines for model operations
implementation "com.github.marcherdiego.mvp:coroutines:LATEST_VERSION" 

Usage

There are three different options to integrate this MVP library to your application, either extending a BaseActivity/BaseFragment that handles all the wiring and setup automagically (recommended), having a reference to the presenter within your Activity/Fragment, or using behaviours. For the three of them, the model, view and presenter behave the same so the only difference is in the activity/fragment

Extending BaseActivity (recommended)

Activity

// Extending BaseActivity will automatically register and unregister the presenter to the bus whenever your activity get resumed or paused
class FeatureActivity : BaseActivity<FeaturePresenter>() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.feature_activity)

        presenter = FeaturePresenter(
                FeatureView(this),
                FeatureModel()
        )
    }
}

Fragment

// Extending BaseFragment will automatically register and unregister the presenter to the bus whenever your activity get resumed or paused
class FeatureFragment : BaseFragment<FeaturePresenter>() {
    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.fragment_example, container, false)
    }

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)

        presenter = FeaturePresenter(
                FeatureView(this),
                FeatureModel()
        )
    }
}

Holding a presenter reference (without inheritance)

Activity

class FeatureActivity : AppCompatActivity() {
    private lateinit var presenter: FeaturePresenter
    private var bus = Bus.newInstance

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.feature_activity)

        presenter = FeaturePresenter(
                FeatureView(this),
                FeatureModel(),
                bus
        )
    }

    override fun onResume() {
        super.onResume()
        bus.register(presenter)
    }

    override fun onPause() {
        bus.unregister(presenter)
        super.onPause()
    }
}

Fragment

class FeatureFragment : Fragment() {
    private lateinit var presenter: FeaturePresenter
    private var bus = Bus.newInstance

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.fragment_example, container, false)
    }

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)

        presenter = FeaturePresenter(
                FeatureView(this, bus),
                FeatureModel(bus)
        )
    }

    override fun onResume() {
        super.onResume()
        bus.register(presenter)
    }

    override fun onPause() {
        bus.unregister(presenter)
        super.onPause()
    }
}

MVP components

Presenter

class FeaturePresenter(view: FeatureView, model: FeatureModel) : BaseActivityPresenter<FeatureView, FeatureModel>(view, model) {
    //...
}

View

class FeatureView(activity: FeatureActivity) : BaseActivityView(activity) {
    //...
}

Model

class FeatureModel : BaseEventsModel() {
    //...
}

Basic wiring

Presenter

class FeaturePresenter(view: FeatureView, model: FeatureModel) : BaseActivityPresenter<FeatureView, FeatureModel>(view, model) {
    // Event posted by the view
    @Subscribe
    fun onActionClicked(event: FeatureView.ActionClickedEvent) {
        view.setTextValue("Executing background task...")
        model.doSomethingInBackground()
    }

    // Event posted by the model
    @Subscribe
    fun onBackgroundTaskCompleted(event: FeatureModel.BackgroundTaskCompletedEvent) {
        view.setTextValue("Background task completed")
    }
}

View

class FeatureView(activity: AppCompatActivity) : BaseActivityView(activity) {
    private var textView: TextView = activity.findViewById(R.id.text)

    init {
        // Helper library method to handle click event
        onClick(R.id.some_button, ActionClickedEvent())
        
        // Optionally you can do
        activity.findViewById<View>(R.id.some_button)?.setOnClickListener {
            bus.post(ActionClickedEvent())
        }
    }

    fun setTextValue(value: CharSequence) {
        textView.text = value
    }

    class ActionClickedEvent
}

Model

import com.nerdscorner.mvplib.events.model.BaseEventsModel

class FeatureModel : BaseEventsModel() {
    fun doSomethingInBackground() {
        backendCall().execute {
            success = {
                bus.post(BackgroundTaskCompletedEvent())
            }
        }
    }

    class BackgroundTaskCompletedEvent
}

Coroutines example

import com.nerdscorner.events.coroutines.extensions.withResult

class FeatureModel : BaseEventsModel() {
    private var fetchJob: Job? = null

    fun doSomethingInBackground() {
        fetchJob = withResult(
            resultFunc = someSuspendFunctionHere(),
            success = { // this: SuspendFunctionReturnType
                bus.post(BackgroundTaskCompletedEvent(this))
            },
            fail = { // this: Exception
                bus.post(BackgroundTaskFailedEvent(this.message))
            },
            cancelled = { // Called when executing fetchJob?.cancel()
                Log.e("InheritanceMainModel", "Job cancelled :(")
            }
        )
    }

    fun cancelJob() {
        fetchJob?.cancel()
    }

    class BackgroundTaskCompletedEvent(val pageHtml: String?)
    class BackgroundTaskFailedEvent(val message: String?)
}

Contributing

Please fork this repository and contribute back using pull requests.

Any contributions, large or small, major features, bug fixes, unit tests are welcomed and appreciated but will be thoroughly reviewed and discussed.

Author

Diego Marcher | diego@marcher.com.uy