Lifecycle : ON_DESTROY & ON_CREATE are called after config_change even when a retained Fragment is used as LifecycleOwner

[viraj49]

I came across this unexpected behaviour when using AAC-Lifecycle alpha5, where I am using a retained fragment as a LifecycleOwner and a regular class as LifecycleObserver and upon configuration change (orientation change), my Fragment's onDestroy & onCreate were not called as expected, but my Observer class's onDestroy & onCreate methods were called, which was strange for me.

Is this a bug with AAC-Lifecycle or issue with my implementation or am I missing something here?

Here is the code I used,

    compile "android.arch.lifecycle:runtime:1.0.0-alpha5"
    compile "android.arch.lifecycle:extensions:1.0.0-alpha5"
    annotationProcessor "android.arch.lifecycle:compiler:1.0.0-alpha5"

Activity.kt

class Activity : LifecycleActivity() {

    private val TAG = "Activity"

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity)
        Log.e(TAG, "OnCreate")

        if (savedInstanceState == null) {
            supportFragmentManager
                    .beginTransaction()
                    .replace(R.id.frame_layout, Fragment())
                    .commit()
        }
    }

    override fun onDestroy() {
        Log.e(TAG, "OnDestroy")
        super.onDestroy()
    }
}

Fragment.kt

class Fragment : LifecycleFragment() {

    private val TAG = "Fragmemt"
    private val observer = Observer()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        retainInstance = true
        lifecycle.addObserver(observer)
        Log.e(TAG, "OnCreate")
    }

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

    override fun onDestroy() {
        Log.e(TAG, "OnDestroy")
        lifecycle.removeObserver(observer)
        super.onDestroy()
    }
}

Observer.kt

class Observer : LifecycleObserver {

    private val TAG = "Observer"

    @OnLifecycleEvent(Lifecycle.Event.ON_CREATE)
    fun onCreate() {
        Log.e(TAG, "onCreate")
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
    fun onDestroy() {
        Log.e(TAG, "onDestroy")
    }
}

[JoseAlcerreca]

I can't find an obvious answer but before taking a closer look, have you tried alpha8?

[viraj49]

I just tried with alpha8, unfortunately it's reproducible with alpha8 as well.

    compile "android.arch.lifecycle:runtime:1.0.0-alpha8"
    compile "android.arch.lifecycle:extensions:1.0.0-alpha8"
    annotationProcessor "android.arch.lifecycle:compiler:1.0.0-alpha8"

E/Activity: OnCreate
E/Fragmemt: OnCreate
E/Observer: onCreate
E/Activity: OnDestroy
E/Observer: onDestroy
E/Activity: OnCreate
E/Observer: onCreate

[pcqpcq]

I think it's the same issue with #47

[ianhanniballake]

Feel free to file a bug against Lifecycle on the issue tracker if this is still an issue.