MVP Helpers

This library exposes a minimal API, that should help you to build well architected Android Apps. ¡Check the following steps to get up and running!

Installation

Actually I don't have this library in JCenter/Maven Central, so if you want to use, follow the instructions. The library is distributed for Java and Kotlin. Looking for Kotlin variant? Go here

Gradle

• Add it in your root build.gradle at the end of repositories:

allprojects {
 repositories {
  ...
  maven { 
   url "https://jitpack.io" 
  }
 }
}

• Add the dependency:

dependencies {
  compile 'com.github.BlackBoxVision:mvp-helpers:v0.2.0'
}

Maven

• Add this line to repositories section in pom.xml:

<repositories>
 <repository>
    <id>jitpack.io</id>
   <url>https://jitpack.io</url>
 </repository>
</repositories>

• Add the dependency:

<dependency>
  <groupId>com.github.BlackBoxVision</groupId>
  <artifactId>mvp-helpers</artifactId>
 <version>v0.2.0</version>
</dependency>

SBT

• Add it in your build.sbt at the end of resolvers:

  resolvers += "jitpack" at "https://jitpack.io"

• Add the dependency:

  libraryDependencies += "com.github.BlackBoxVision" % "mvp-helpers" % "v0.2.0" 

Core Concepts

The concepts behind this library are the following ones:

• View → The View is an interface that contains methods related to UI interaction. Those methods should be implemented in your Activity, Fragment or View.

• Interactor → The Interactor is the class that do the hard work, all the blocking operations like I/O, Networking, Database Intectations should be done here.

• Presenter → The presenter acts as a middle man between the Interactor and the View.

Usage example

The usage is really simple:

1 - Create your View interface by extending the BaseView. BaseView is an empty interface that acts as water mark for the Presenter.

public interface DetailsView extends BaseView {

    void onInfoReceived(@NonNull Bundle information);

    void onInfoError(@NonNull String errorMessage);
}

2 - Create an Interactor class by extending the BaseInteractor class. The BaseInteractor provides you a set of helper methods to deal with background execution and UIThread interaction. The methods are the following ones:

• runOnUiThread → use it when you need to post data to the main thread.
• runOnBackground → use it when you need to make background processing.
• runOnBackground → use it when you need to make a scheduled task.
• cancelTask → use it when you want to cancel a scheduled task.

//This example uses Java 8 features, I assume the usage of retrolambda
public final class DetailsInteractor extends BaseInteractor {

    public void retrieveDetailsFromService(@NonNull final String id, @NonNull final OnSuccessListener<Bundle> successListener, @NonNull final OnErrorListener<String> errorListener) {
        runOnBackground(() -> {
            //Getting data from somewhere
            final Bundle data = MockUtils.getMockedData(id);

            runOnUiThread(() -> {
                if (data != null) {
                    successListener.onSuccess(data);
                } else {
                    errorListener.onError("Ups, something went wrong");
                } 
            });
        });
    }
}

3 - Create a Presenter class by extending the BasePresenter class. The BasePresenter provides you with a set of helper methods to deal with View management. The methods are the following ones:

• isViewAttached → check if you have set the view to the presenter, returns to you a boolean value that you should handle in your presenter implementation.
• attachView → add the view to the presenter, so you can start to handle the cycle of view - presenter - interactor interaction.
• detachView → dereference the view, setting it to null. This method should be called in the onDestroy method in case of use in Activity, and onDestroyView in case of Fragment usage.
• getView → simple getter, to make your access to the view defined more cleaner.
• onViewAttached → callback fired when the view is attached to the presenter, it gives you the view so you can start doing something like restoring state, instantiating the interactors.
• onViewDetached → callback fired when the view is detached from the presenter, in this place you can dereference the objects you won't use anymore.

//I use method references from Java 8 to point the callbacks to interactor, I assume a working project with Retrolambda
public final class DetailsPresenter extends BasePresenter<DetailsView> {
    private DetailsInteractor interactor;
    
    @Override
    protected void onViewAttached(@NonNull DetailsView view) {
        interactor = new DetailsInteractor();
    }

    @Override
    protected void onViewDetached() {
        interactor = null;
    }

    public void findRequiredInformation(@NonNull String id) {
        if (isViewAttached()) {
            interactor.retrieveDetailsFromService(id, this::onSuccess, this::onError);
        }
    }

    private void onSuccess(@NonNull Bundle information) {
        if (isViewAttached()) {
            getView().onInfoReceived(information);
        }
    }

    private void onError(@NonNull String errorMessage) {
        if (isViewAttached()) {
            getView().onInfoError(errorMessage);
        }
    }
}

4 - Create a custom PresenterFactory class to provide the presenter instance. You should implement the PresenterFactory interface.

Now we have to create a Factory, because I have recently implemented a way to not loose presenter when configuration changes. The BaseActivity/BaseFragment use a Loader to provide the Presenter instance, Android Loaders can survive configuration changes, that's why I select them.

class DetailsPresenterFactory implements PresenterFactory<DetailsPresenter> {
 
 @Override
 public DetailsPresenter create() {
  return new DetailsPresenter();
 }
}

5 - Attach this cycle with Android specific classes. You can choice an Activity/Fragment or also a custom view. In this case I will show you an example with Fragment that inherits from BaseFragment

The BaseFragment comes with a resumed lifecycle, and a set of methods to implement. The methods are the following ones:

• createPresenterFactory → in this method you have to create an instance of PresenterFactory.
• getLayout → in this method you have pass the id reference to the layout.
• getPresenter → simple getter, to make your access to the presenter more cleaner.
• onPresenterCreated → In this method you can start doing something with the presenter. ¡Now the View is attached automatically to the Presenter!
• onPresenterDestroyed → In this method you can do something, like saving app state.

public final class DetailsFragment extends BaseFragment<DetailsPresenter, DetailsView> implements DetailsView {
    
    @Override
    protected DetailsPresenterFactory createPresenterFactory() {
       return new DetailsPresenterFactory();
    }
    
    @LayoutRes
    @Override
    protected int getLayout() {
       return R.layout.fragment_details;
    }
    
    @Override
    protected void onPresenterCreated(@NonNull DetailsPresenter presenter) {
     //Do something when presenter it's created
     getPresenter().getInformationFromId("ssdWRGD132");
    }
    
    @Override
    protected void onPresenterDestroyed() {
     //Do something when presenter is removed, this method is called in onDestroy 
    }
    
    @Override
    void onInfoReceived(@NonNull Bundle information) {
       Toast.makeText(getContext(), information.toString(), Toast.LENGTH_SHORT).show();
    }
    
    @Override
    void onInfoError(@NonNull String errorMessage) {
       Toast.makeText(getContext(), errorMessage, Toast.LENGTH_SHORT).show();
    }
} 

Advise about ButterKnife

From version 0.2.0 of this library, I have decided to remove butterKnife, in order to not force any dev to use butterKnife.

Issues

If you found a bug, or you have an answer, or whatever. Please, open an issue. I will do the best to fix it, or help you.

Contributing

Of course, if you see something that you want to upgrade from this library, or a bug that needs to be solved, PRs are welcome!

Release History

• 0.2.0

  • CHANGE: BasePresenter has now two new callbacks, to be notified about view attachment/detachment.
  • CHANGE: BaseActivity/BaseFragment has now two new callbacks to be notified about presenter creation/destruction, also, addPresenter callback has been replace with createPresenterFactory
  • CHANGE: Added PresenterFactory interface to create custom factories to provide presenter instances
  • CHANGE: Added PresenterLoader, an Android Loader, that provides the presenter instance and survives configuration changes.
  • BUG FIX: Fixed issue with BaseInteractor runOnBackground method, this method was calling executor.isTerminated instead of calling executor.isShutdown, this produce a RuntimeException, because of troubles with ThreadPool reuse. Also, the methods have been refactored, to use a ExecutorService to get more control instead of an Executor.

• 0.1.0

  • CHANGE: Folder refactor under UI package
  • CHANGE: Modified BasePresenter method registerView to attachView in order to get more consistence
  • CHANGE: Added new runOnBackground version in BaseInteractor that uses a ScheduledExecutorService and also cancel method to stop execution
  • CHANGE: Added Custom Views to extend BaseRelativeLayout, BaseFrameLayout and BaseLinearLayout

• 0.0.3

  • CHANGE: Removed ButterKnife annotation processor
  • CHANGE: Rename mvphelper library to library

• 0.0.2

  • CHANGE: Minor updates

• 0.0.1

  • Work in progress

License

Distributed under the MIT license. See LICENSE for more information.