LifeCycleBinder

Using LifeCycleBinder you can create Java classes connected to the lifecycle of an Activity or a Fragment.

The usage is simple, you just need to create a class that implements LifeCycleAware and modify your Activity/Fragment adding a field annotated with @BindLifeCycle and invoking LifeCycleBinder.bind(this) in onCreate method.

If you want to create an object that survives on configuration changes you can annotate a Callable or a Provider field using @RetainedObjectProvider annotation.

Usage

In this example we are using a field annotated with @BindLifeCycle. We don't need to extend a custom base class, we just invoke the LifeCycleBinder.bind static method:

public class MyActivity extends AppCompatActivity {
    @BindLifeCycle
    MyLifeCycleAware myLifeCycleAware = new MyLifeCycleAware();

    private TextView textView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        textView = new TextView(this);
        setContentView(textView);

        LifeCycleBinder.bind(this);
    }

    public void setText(String text) {
        textView.setText(text);
    }
}

The MyLifeCycleAware class must implement LifeCycleAware interface, the class DefaultLifeCycleAware can be used to override only some methods:

public class MyLifeCycleAware extends DefaultLifeCycleAware<MyActivity> {
    @Override
    public void onCreate(MyActivity view, Bundle savedInstanceState, Intent intent, Bundle arguments) {
        view.setText("Hello world!");
    }
}

The first parameter of LifeCycleAware methods is always the Activity or the Fragment. An interface or a base class can be used to avoid dependency to Android classes. The other parameters are usually the same parameters of the corresponding Activity/Fragment method, there are two exceptions:

onCreate method contains the Activity intent and a Bundle (it can be the Activity intent bundle or the Fragment arguments);
onDestroy method contains a changingConfigurations parameters.

Using LifeCycleBinder it's easy to manage retained objects, we can create an Activity with a Callable field annotated with @RetainedObjectProvider:

@RetainedObjectProvider
Callable<MyRetainedLifeCycleAware> myFactory = () -> new MyRetainedLifeCycleAware();

In this example a MyRetainedLifeCycleAware object is created on the first start, all the callbacks are invoked on this object. If the Activity/Fragment is destroyed for a configuration change the object is retained. In case we need to use this object directly we can create a field and add the field name as parameter to the @RetainedObjectProvider annotation:

MyRetainedLifeCycleAware myRetainedLifeCycleAware;

@RetainedObjectProvider("myRetainedLifeCycleAware")
Callable<MyRetainedLifeCycleAware> myFactory = () -> new MyRetainedLifeCycleAware();

LifeCycleAware interface contains the methods to manage option menu:

boolean hasOptionsMenu(T view)
void onCreateOptionsMenu(T view, Menu menu, MenuInflater inflater)
boolean onOptionsItemSelected(T view, MenuItem item)

Activity navigation can be managed using LifeCycleBinder, LifeCycleAware interface contains onActivityResult method that it's invoked when an Activity returns. LifeCycleBinder class contains a static method startActivityForResult, you need to use this method passing the Activity/Fragment to receive the callback.

How does it work under the hood?

LifeCycleBinder creates a new Fragment with no user interface and adds it to the Activity or the Fragment. This new Fragment manages the lifecycle and invokes the methods on the registered objects. Annotated objects are collected using an annotation processor.

Retained objects are managed using a Loader associated to the Fragment.

LifeCycleBinder depends on support-v4 v24, it uses the new method commitNow to dynamically add the Fragment.

Dagger support

LifeCycleBinder can be easily used on objects managed by Dagger 2. @BindLifeCycle works on fields populated using @Inject annotation, @RetainedObjectProvider can be used on Provider fields. The previous examples can be rewritten using Dagger:

@Inject
@BindLifeCycle
MyLifeCycleAware myLifeCycleAware;

MyRetainedLifeCycleAware myRetainedLifeCycleAware;

@Inject
@RetainedObjectProvider("myRetainedLifeCycleAware")
Provider<MyRetainedLifeCycleAware> myFactory;

JitPack configuration

LifeCycleBinder is available on JitPack, add the JitPack repository in your build.gradle (in top level dir):

repositories {
    jcenter()
    maven { url "https://jitpack.io" }
}

and the dependency in the build.gradle of the module:

dependencies {
    annotationProcessor 'com.github.fabioCollini.lifecyclebinder:lifecyclebinder-processor:0.3.2'
    compile 'com.github.fabioCollini.lifecyclebinder:lifecyclebinder-lib:0.3.2'
}

License