ThirtyInch - a MVP library for Android

This library adds Presenters to Activities and Fragments. It favors the stateful Presenter pattern, where the Presenter survives configuration changes and dumb View pattern, where the View only sends user events and receives information from the Presenter but never actively asks for data. This makes testing very easy because no logic lives in the View (Activity, Fragment) except for fancy animations which anyways aren't testable.

The name

Keep Android At Arm’s Length

— Kevin Schultz, Droidcon NYC '14

The perfect distance to the Android Framework is approximately thirty inches, the average length of the human arm, shoulder to fingertips.

Story

Read the introduction article on Medium

See the slides of the latest talk on Speakerdeck

Get it

ThirtyInch is available via jcenter

dependencies {
    def thirtyinchVersion = '0.8.0'
    
    // MVP for activity and fragment
    compile "net.grandcentrix.thirtyinch:thirtyinch:$thirtyinchVersion"
    
    // rx (1 or 2) extension
    compile "net.grandcentrix.thirtyinch:thirtyinch-rx:$thirtyinchVersion"
    compile "net.grandcentrix.thirtyinch:thirtyinch-rx2:$thirtyinchVersion"
    
    compile "net.grandcentrix.thirtyinch:thirtyinch-logginginterceptor:$thirtyinchVersion"
    
    // test extension
    testCompile "net.grandcentrix.thirtyinch:thirtyinch-test:$thirtyinchVersion"
    
     
    // CompositeAndroid plugin
    // When you are using ThirtyInch with the CompositeAndroid extension you have to manually 
    // include the CompositeAndroid dependency. It has to be the same version as appcompat and 
    // the support library 
    
    compile "net.grandcentrix.thirtyinch:thirtyinch-plugin:$thirtyinchVersion"
    // def supportLibraryVersion = '24.2.1' <-- use your own version
    compile "com.pascalwelsch.compositeandroid:activity:$supportLibraryVersion"
}

ThirtyInch sample project (work in progress)

There is a sample implementation based on the Android Architecture Blueprints TODO app which can be found here: ThirtyInch sample project (work in progress)

Hello World MVP example with ThirtyInch

HelloWorldActivity.java

public class HelloWorldActivity 
        extends TiActivity<HelloWorldPresenter, HelloWorldView> 
        implements HelloWorldView {

    private TextView mOutput;

    @NonNull
    @Override
    public HelloWorldPresenter providePresenter() {
        return new HelloWorldPresenter();
    }

    @Override
    public void showText(final String text) {
        mOutput.setText(text);
    }

    @Override
    protected void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_hello_world);

        mOutput = (TextView) findViewById(R.id.output);
    }
}

HelloWorldView.java

public interface HelloWorldView extends TiView {

    @CallOnMainThread
    void showText(final String text);
}

HelloWorldPresenter.java

public class HelloWorldPresenter extends TiPresenter<HelloWorldView> {

    @Override    
    protected void onAttachView(@NonNull final HelloWorldView view) {
        super.onAttachView(view);
        view.showText("Hello World!");
    }
}

ThirtyInch features

Presenter

• survives configuration changes
• survives when the Activity got killed in background
• is not a singleton
• dies when the Activity gets finished

Lifecycle

The TiPresenter lifecycle is very easy.

It can be CREATED and DESTROYED. The corresponding callbacks onCreate() and onDestroy() will be only called once!

The TiView can either be ATTACHED or DETACHED. The corresponding callbacks are onAttachView(TiView) and onDetachView() which maps to onStart() and onStop().

public class MyPresenter extends TiPresenter<MyView> {

    @Override
    protected void onCreate() {
        super.onCreate();
    }

    @Override
    protected void onAttachView(@NonNull final HelloWorldView view) {
        super.onAttachView(view);
    }

    @Override
    protected void onDetachView() {
        super.onDetachView();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
    }
}

The lifecycle can be observed using TiLifecycleObserver

There is no callback for onResume() and onPause() in the TiPresenter. This is something the view layer should handle. Read more about this here Hannes Dorfmann - Presenters don't need lifecycle events

Configuration

The default behaviour might not fit your needs. You can disable unwanted features by providing a configuration in the TiPresenter constructor.

public class HelloWorldPresenter extends TiPresenter<HelloWorldView> {

    public static final TiConfiguration PRESENTER_CONFIG = 
            new TiConfiguration.Builder()
                .setRetainPresenterEnabled(true) 
                .setCallOnMainThreadInterceptorEnabled(true)
                .setDistinctUntilChangedInterceptorEnabled(true)
                .build();
            
    public HelloWorldPresenter() {
        super(PRESENTER_CONFIG);
    }
}

Or globally for all TiPresenters

public class MyApplication extends Application {

    @Override
    public void onCreate() {
        super.onCreate();
        TiPresenter.setDefaultConfig(MY_DEFAULT_CONFIG);
    }
}

TiView Annotations

Two awesome annotations for the TiView interface made it already into Ti saving you a lot of time.

public interface HelloWorldView extends TiView {

    @CallOnMainThread
    @DistinctUntilChanged
    void showText(final String text);
}

@CallOnMainThread

Whenever you call this method it will be called on the Android main thread. This allows to run code off the main thread but send events to the UI without dealing with Handlers and Loopers.

Requires to be a void method. Works only for TiView interfaces implemented by "Android Views" (TiActivity, TiFragment).

Enabled by default, can be disabled with the TiConfiguration

@DistinctUntilChanged

When calling this method the View receives no duplicated calls. The View swallows the second call when a method gets called with the same (hashcode) parameters twice.

Usecase: The Presenter binds a huge list to the View. The app loses focus (onDetachView()) and the exact same Activity instance gains focus again (onAttachView(view)). The Activity still shows the huge list. The Presenter binds the huge list again to the View. When the data has changed the list will be updated. When the data hasn't changed the call gets swallowed and prevents flickering.

Requires to be a void method and has at least one parameter.

Enabled by default, can be disabled with the TiConfiguration

View binding interceptors

View Annotations only work because ThirtyInch supports interceptors. Add interceptors (BindViewInterceptor) to TiActivity or TiFragment to intercept the binding process from TiView to TiPresenter. Interceptors are public API waiting for other great ideas.

public class HelloWorldActivity extends TiActivity<HelloWorldPresenter, HelloWorldView>
        implements HelloWorldView {

    public HelloWorldActivity() {
        addBindViewInterceptor(new LoggingInterceptor());
    }
}

LoggingInterceptor is available as module and logs all calls to the view.

RxJava

Using RxJava for networking is very often used. Observing a Model is another good usecase where Rx can be used inside of a TiPresenter. The Rx package provides helper classes to deal with Subscription or wait for an attached TiView.

public class HelloWorldPresenter extends TiPresenter<HelloWorldView> {

    // add the subscription helper to your presenter
    private RxTiPresenterSubscriptionHandler rxHelper = new RxTiPresenterSubscriptionHandler(this);

    @Override
    protected void onCreate() {
        super.onCreate();
        
        // automatically unsubscribe in onDestroy()
        rxHelper.manageSubscription(
                Observable.interval(0, 1, TimeUnit.SECONDS)
                    // cache the latest value when no view is attached
                    // emits when the view got attached
                    .compose(RxTiPresenterUtils.<Long>deliverLatestToView(this))
                    .subscribe(uptime -> getView().showPresenterUpTime(uptime))
        );
    }

    @Override
    protected void onAttachView(@NonNull final HelloWorldView view) {
        super.onAttachView(view);
        
        // automatically unsubscribe in onDetachView(view)
        rxHelper.manageViewSubscription(anotherObservable.subscribe());
    }
}

CompositeAndroid

Extending TiActivity is probably not what you want because you already have a BaseActivity. Extending all already existing Activities from TiActivity doesn't make sense because they don't use MVP right now. CompositeAndroid uses composition to add a TiPresenter to an Activity. One line adds the TiActivityPlugin and everything works as expected.

public class HelloWorldActivity extends CompositeActivity implements HelloWorldView {

    public HelloWorldActivity() {
    
        // Java 7
        addPlugin(new TiActivityPlugin<>(
                new TiPresenterProvider<HelloWorldPresenter>() {
                    @NonNull
                    @Override
                    public HelloWorldPresenter providePresenter() {
                        return new HelloWorldPresenter();
                    }
                }));

        // Java 8
        addPlugin(new TiActivityPlugin<HelloWorldPresenter, HelloWorldView>(
                () -> new HelloWorldPresenter()));
    }
}

Yes you have to extend CompositeActivity, but that's the last level of inheritance you'll ever need.

License

Copyright 2016 grandcentrix GmbH

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.