ActivitiesTracker

ActivitiesTracker.kt

import android.annotation.SuppressLint
import android.app.Activity
import android.app.Application
import android.os.Bundle
import timber.log.Timber
import java.lang.ref.WeakReference

class ActivitiesTracker {

    private val createdActivities = mutableListOf<WeakReference<Activity>>()
    private val startedActivities = mutableListOf<WeakReference<Activity>>()

    @SuppressLint("BinaryOperationInTimber")
    fun init(app: Application) {
        app.registerActivityLifecycleCallbacks(
            object : Application.ActivityLifecycleCallbacks {

                override fun onActivityCreated(activity: Activity, savedInstanceState: Bundle?) {
                    createdActivities.addDistinct(activity)
                    Timber.d("[ActivitiesTracker] created: " +
                            "${activity}, ${createdActivities.size}")
                }

                override fun onActivityStarted(activity: Activity) {
                    startedActivities.addDistinct(activity)
                }

                override fun onActivityResumed(activity: Activity) {}

                override fun onActivityPaused(activity: Activity) {}

                override fun onActivityStopped(activity: Activity) {
                    startedActivities.removeLastActivity(activity)
                }

                override fun onActivitySaveInstanceState(activity: Activity, outState: Bundle) {}

                override fun onActivityDestroyed(activity: Activity) {
                    createdActivities.removeLastActivity(activity)
                    Timber.d("[ActivitiesTracker] destroyed: " +
                            "${activity}, ${createdActivities.size}")
                }
            }
        )
    }

    @Suppress("Unused")
    fun getCreated(): Activity? = createdActivities.getLastExisting()

    @Suppress("Unused")
    fun getStarted(): Activity? = startedActivities.getLastExisting()

    @Suppress("Unused")
    fun allCreated(): List<Activity> =
        createdActivities.mapNotNull { it.get() }

    @Suppress("Unused")
    fun finishAllExcept(except: Activity) {
        allCreated().forEach { activity ->
            if (activity != except) {
                Timber.d("[ActivitiesTracker] finish: $activity")
                activity.finishAndRemoveTask()
            }
        }
    }

    private fun List<WeakReference<Activity>>.getLastExisting(): Activity? {
        if (BuildConfig.DEBUG) {
            forEach {
                Timber.d("[ActivitiesTracker] getLastExisting list: ${it.get()}")
            }
        }
        asReversed().forEach {
            val activity = it.get()
            if (activity != null) {
                return activity
            }
        }
        return null
    }

    private fun MutableList<WeakReference<Activity>>.removeLastActivity(activity: Activity) {
        val asReversed = asReversed()
        asReversed.forEachIndexed { index, weakReference ->
            val fromRef = weakReference.get()
            if (fromRef === activity) {
                asReversed.removeAt(index)
                return
            }
        }
    }

    private fun MutableList<WeakReference<Activity>>.addDistinct(activity: Activity) {
        if (!containsActivity(activity)) {
            add(activity.weak())
        }
    }

    private fun List<WeakReference<Activity>>.containsActivity(activity: Activity) =
        any { it.get() === activity }

    private fun Activity.weak() = WeakReference(this)
}