LightCycle is an Android library that helps break logic out of Activity and Fragment classes into small, self-contained components called LightCycles.

Fields that are annotated @LightCycle and implement the LightCycle API within a LightCycleActivity or LightCycleFragment will be bound to that Activity or Fragment lifecycle.

public class MyActivity extends LightCycleAppCompatActivity<MyActivity> {
    @LightCycle MyController controller = new MyController();

    @Override
    protected void setActivityContentView() {
        setContentView(R.layout.main);
    }
}

public class MyController extends DefaultActivityLightCycle<MyActivity> {

    @Override
    public void onPause(MyActivity activity) {
        // MyActivity was paused
    }
    
    [...]

    @Override
    public void onResume(MyActivity activity) {
        // MyActivity was resumed
    }
}

LightCycle lets self-contained classes respond to Android’s lifecycle events. This supports composition over inheritance and promotes components that follow the single responsibility principle. We believe it helps us write more readable, maintainable and testable code. It works particularly well alongside dependency injection.

• Activity & Fragment classes:
• Inflate layouts and configure Android specifics
• Declare LightCycles
• A LightCycle component is responsible for an isolated chunk of logic (such as presentation, tracking etc.)

A LightCycle doesn't know about other LightCycles. There is no guarantee for ordering when multiple LightCycles receive the same lifecycle callback.

• basic
• "real world"

There are 3 types of LightCycles - the API is comparable to the ActivityLifecycleCallbacks from the Android SDK:

• ActivityLightCycle
• FragmentLightCycle
• SupportFragmentLightCycle

For convenience, default implementations are provided:

• DefaultActivityLightCycle
• DefaultFragmentLightCycle
• DefaultSupportFragmentLightCycle

This dispatches an Activity or Fragment lifecycle callback to attached LightCycles. The API defines a single bind method. See the LightCycleDispatcher interface.

Three types of dispatchers are provided:

• ActivityLightCycleDispatcher
• FragmentLightCycleDispatcher
• SupportFragmentLightCycleDispatcher

Note: these built-in classes are both dispatchers and LightCycles, meaning that you can nest LightCycles.

public class MyActivity extends LightCycleAppCompatActivity<MyBaseActivity> {
    @LightCycle MyController controller = new MyController();

    @Override
    protected void setActivityContentView() {
        setContentView(R.layout.main);
    }
}

public class MyController extends ActivityLightCycleDispatcher<MyActivity> {
    @LightCycle MySubController1 controller = new MyController1();
    @LightCycle MySubController2 controller = new MyController2();

    @Override
    public void onCreate(Bundle savedInstanceState) {
        [...] // <- specific init 
        super.onCreate(savedInstanceState) // <- call super to dispatch.
    }
}

The following base activities are provided so far:

• LightCycleActionBarActivity
• LightCycleAppCompatActivity
• LightCycleFragment
• LightCycleSupportFragment

To add LightCycles to your MyBaseActivity, your Activity must:

• Implement the LightCycleDispatcher interface
• Dispatch all the lifecycle methods
• Bind fields annotated @LightCycle with LightCycles.bind(this)

The same technique applies for Fragment.

public class MyBaseActivity extends Activity implements LightCycleDispatcher<ActivityLightCycle<MyBaseActivity>> {

    private final ActivityLightCycleDispatcher<MyBaseActivity> lightCycleDispatcher;

    @Override
    public void bind(ActivityLightCycle<MyBaseActivity> lightCycle) {
        lightCycleDispatcher.bind(lightCycle);
    }
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        LightCycles.bind(this);
        lightCycleDispatcher.onCreate((MyBaseActivity) this, savedInstanceState);
    }
    
    [...]
    
    @Override
    protected void onDestroy() {
        lightCycleDispatcher.onDestroy((MyBaseActivity) this);
        super.onDestroy();
    }
}

See for example LightCycleActionBarActivity or LightCycleSupportFragment.

Gradle:

buildscript {
  dependencies {
    classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8'
  }
}

apply plugin: 'com.neenbedankt.android-apt'

ext.lightCycleVersion=<LATEST_VERSION>

dependencies {
  compile 'com.soundcloud.lightcycle:lightcycle-lib:$lightCycleVersion'
  apt 'com.soundcloud.lightcycle:lightcycle-processor:$lightCycleVersion'
}